Why? do fuses blow?, answer , "to prevent the fire" that would happen as the wires glow red hot.
The battery can produce 500 amps. (over 5000 watts of energy) or 6.7 Horse Power of pure energy. Or 50 times , 100watt light bulbs. (or 3 hair dryers)
The Fuse prevents the fire , by interrupting this faulting path.
It can protect the igniton switch from blowing out, and the $300 combo switch melt down. Do not increase fuse sizes (ratings)
How to remove your SHORTS?
A short is when any feed power wire (12vdc) accidentally gets connected to ground.
A short is an electrical request for infinite energy, a very bad state, or condition.
Partial shorts or leakage paths, that drain batteries "dead or weak" overnight are called drains. ( look for lamps stuck on everywhere on car)
Phantom drains are key off illegal current flows. over about 0.050 amps. A car stalls and the battery is dead, running, is a failing charge system.
For Phantom DRAINS (dark current )
The techniques for finding phantoms drains and dead shorts are the same, use an Ammeter and pull fuses, with a valid schematic in your hand.
See how to find a non EFI "electronic fuel injection" a short in the PARK /TAIL/ Running lamp circuit .
Diagnostic Methodology:
The best way to find any short is to pull connectors and all loads, until the fuse stops blowing the last pulled connection, that ends the blow out, is the bad component.
What is a load?, it is anything connected , that is not a wire or connector. The most complex circuit is the PARK (tail) path.
A load is an object that uses power to operate , a radio is a load, a blower fan is a load.
So are EFI sensors.... and all modules on the car. PCM/TCM./Cruise/ and many others, and all lamps in the car are loads.
Many shorts can be found just look (inspecting )the ends of all harneess in the car, if that looks good, why not look at the whole harness system?
See Duane's fine video.. No start, dead CEL , lost power 12vdc to ECU/PCM and fuse F20 blows, over and over , last he finds 02 sensor shorted. (wires)
Note he uses real diagrams, and never GUE$$e$ and an ammeter to trace the shorted path. You don't need Duanes expensive beeper, any $10 volt meter works.
See Chris video how to find shorts; he has a KEY off DRAIN and finds stuck on fog lamp. This video is to see how he pulls fuses, to find the load stuck on.
Chris's method is no good for a dead short because that blows out the meter internal amps fuse. 10 or 20 amps. His drain was 9 amps. (huge)
Best is AMPCLAMP or use this .
or use the Short finder (tm)
The normal key off drain is 0 to 0.040 amps, 40 mA max, 0.1 bad, 0.2 bad, 0.050 iffy. (depends on year car and all those silly extra computers added, lots)
There are many fuses, and most have many loads to just one fuse, any one of which, can short and if not protected with a fuse, the wire will catch fire and burn.
This is called a SHORTED out circuit, it means a power feed is grounding out, or crossed over from power to ground. Any feed.
A power feed is a source of power from the battery to some device, something that needs 12 vdc power to function correctly. (lights and electronics, and soleniods)
Think of a the cars wiring like a tree, we find which part ,or branch , has a short?, then what LEAF is shorted. See? Or which fruit is shorted out.
The FSM calls these schematics, the Power Distribution pages. Newer cars have like 30 pages of them , vast ways to short. (not this car, it's simple)
Any part can short, the wire, the connector or the load.
Think of it like water pipes, any pipe in the house or valve can leak. (keep and open mind)
The harness itself, can short out. Some countries call this a LOOM. (looming shorts?) haha.
These tactics work on all cars, ships, boats, planes or trucks. (even inside modules , this works !)
Goal 1, is to find which fuse NAME blows and what color wire, on that output, of fuse, is shorted. (yes, a schematic will help vastly)
Most fuse outputs, can go to many places, and can meander about the cars harness. (the Park (tail-running) lamps go to up to 20+ places)
The output of this FUSE drives all loads, on this power feed Bus. (it's just a wire that has splices and junction and connectors)
Then we , trace that path. (there are many ways to find a short, I will cover many hard failure paths, on this page, even the profound )
The below covers shorts in the cab box, not the 50-100 amp engine bay fuse box that loves to rust out. (but the techniques, are one in the same)
My page will give examples of many types of shorts. (not all)
Hint 1: This car has hidden connectors all over (last chapter in FSM covers this) and you can use this fact, to great advantage to find a short (pull them)
WAYS to FIND shorts: (the ohmmeter is a poor way, to find a short, (loads attached) for 1 simple reason, lamps read 0 ohms ! cold. (a fact)
- A box of fuses , lots of time and $$$ fuses, and pull all connectors on
that feed, on the whole car, and then put them back 1 by 1, rear to
front of car, bam, now you know which harness section is shorted.
- Use an Ammeter to find the short. (use the
amp clamp meter with the CB below)or use the series analog
Ammeter with this.
- Use
a DMM Ohmmeter (poor way) (don't work on
lamps, say the park circuit as there are 20 lamp shorts there
,normally) But does work on naked harnesses , loads all removed on your
bad PATH.
- Use a Circuit Breaker (CB) in place
of the fuse to
save money on constant blown regular fuses., then detach all loads to
find which branch has the short.
(A TOP WAY)
- Use A D.C.
12volt power pack
supply with current limit, to find shorts super easy. I set it to like
5-20 Amps @12v. and then find the short by pulling loads. (do not do this to ECU output pins)
- You could use a powered
test lamp or any lamp
connected in place of the fuse, to find any short. (An 1157 lamp works good here) The lamp glows when there is a short.
- Some folks even add fuses to very complex wiring, to find a
short, one great place is the fuel
pump feed that loves to short. (behind rear left tail light) I
use 10amps here. (inline fuse holder) Pink wire.
- Use
a TDR tester,
(very expensive)
"it's a radar for wires that finds shorts" It show the exact distance
from test point to the short ! I own this tool to find bad CAT5/6
network cables (a cheap tool)
NO TOOLS Method 6 above will not work on lines with lamps, as they draw too much current , but always works if,you unplug all load devices, say tail lamps. to find an actual harness shorts.
Remember metal brass colored base lamps, love to short inside the base. So, pull them first.
Same is true of way 3. Lamps read a short with all ohmmeters. (means DMM set to Resistance low scale, eg: Ohms) Lamps read 0 ohms cold and way more glowing white hot.
This meter ohms test, does work perfect on all disconnected loads from harnesses. (say, pull all the loads and the fuse blows, do a insulation test with the ohmmeter and expert infinity ohms)
I have used all ways listed above, and all work great.
The CB + amp clamp way wins the game, fast and with no guess work. CB means Circuit breaker, used in place of the fast acting thermal fuse. (stock fuse out)
The fuel pump , draws 4 amps, normally: (a factoid, not in books)
You really should have 2 tools here, and Ammeter and a thermal auto resetting circuit breaker, (20amps) < see Duane's video above for proof.
More tools are here.
I can a find shorts easy ,with my amp clamp Ammeter (DMM). (with the CB fuse inserted, is real easy to find any short)
The tool-less?, must use unplug and pray. Pray the short goes away, pulling loads off line. (this does work and is cost free (except 2 blown fuses) , but slow)
You can use any old school, series shunt ammeter, but you will blow up the meter, unless you use a lamp tester.
You can use this same resistor to test your old series 20 amp meter , that love to blow up its internal fuse.
All modern meters, Amps, are fuse inside, do not blow it out, or fail to check it first. (I always test my meters, before using them.)
You only need 2 things to start; the meter and the schematic here, or at alldata.com DIY.
The Schematic shows you all those branches in the tree and all loads connected to a branch.
The real FSM actually, shows ever inch of the harness and where it goes. and connector views, etc. (real means from the car maker, a book)
FSM = Factory Service Manual.
Here is the circuit breaker tool.
Pull the loads 1 by 1 and see if the fuse holds or not (blows), (have a large box of fuses handy ;as you keep blowing them...$$$)
Or use an Ammeter, most serial Ammeters are NOT DIY friendly ! and the meter blows its' internal fuse confusing the users.
Some meters just blow up, with cloud of smoke. 1970 meters. or older. (some old meters, have no internal protection fuses)
Never connect any ammeter across any power source, AMP meters are serial devices , that is connected in series with any load.
( so , use an Amp clamp tool and fix cars and not have to replace blown meters or fuses, all day. or use the lamp trick.)
I = V/R if V is 12v and R is 1 ohm then 12 amps flows and the 20 amp meter reads 12 amps, if not?, the meter is TOAST.
An AMP CLAMP Ammeter, will not fail you, or blow up, or fail to find the short. (it is, the best of the best in tools)
Most or Cheap Amp. Clamp meters only do A.C. Current and are useless on cars.
Cars use D.C (Direct Current) sourced from a D.C. battery.
You only need 1 or 2 tools:
A DC ammeter and a schematic, the latter is free below, and covers 10 years.
There is a trick to save fuses, Pull all loads in the tree branch, that attach to the fuse that blows, fuse holds now? if not?, the harness is shorted. (see full PDF for all loads)
Trick one : (stuck off road and no tools)?
If you pull all loads first, you only need to blow 2 fuses and the last load connected and blown is the bad load.
Can be done with 1 blown fuse, (Pull all loads, plug in loads, 1 at a time until the fuse blows) BINGO the last load connected is shorted out.
If you have the circuit breaker (CB) adapter , you can do the job in any order. (nice huh?) If fact pull loads until it stops tripping. I carry these tools offroad, way off road.
I'll do the lazy way below, as most do. (a box of fuses handy) No long wait for tools in the mail.
ECU/PCM SHORTS:
This page section below , this example, covers only 1 shorted path, the most difficult of all, all other shorts on car, are vastly (brakes, blinkers,etc) more easy to find.
The Main ECU relay is a tad tricky. (on USA cars, keyone the relay closes, via 1 dumb diode in the ECU)
Be aware that some cars, not in USA, have the Immobilizer controlling the MAIN relay. (I do not cover IMMO issues)
What I do is use my AMP clamp tool to find the wire that is shorted, (eg, at the actual load in question)
The ECU has 3 fuses, IG-coil, "FI" and DOME. The first 2 can short easy with bad CAP.'s inside the ECU. "FI" means Fuel Injection. and Injectors , ECU and Fuel pumps do short.
I will do 2 types of blown fuses, both are common. the IG-COIL and FI fuse blowing.
FI blows is covered here:
CASE #1: Ignition shorts:
The IG-COIL blows over and over. (only, NOT FI) "
The black-white wire is shorting to ground blowing fuses, this is caused by bad devices operating off this power feed.
(a bad harness is rare on un-molested cars , still stock !) But many cars the harness clamps are messed up by owners.
The old 1991 car, 8 valves, is my example: (16v in Red)
Simple tactics:
You pull each of these loads 1 by one to find the short. (or all loads at once and put them back 1by1) (lots of fuses, used , I use my ammeter and circuit breaker)
If no AMP meter in tool box, skip this...
I connect my Amp-clamp to the black-white feed wire at the fuse panel, and turn the Ignition key, the fuse blows and the meter shows a huge short. (a huge pulse then nothing)
(the Amps Display goes over range a huge spike of current and fuse blows, (circuit breaker (CB) trips) There you are , I SEE YOU !
The IG-Fuse does not run the Fuel pump, the FI fuse does that. so don't waste time on the problematic fuel pump this time.
If the FI blows, use the Amp Clamp at the PINK fuel pump feed wire...
I have my IG-fuse replaced with my CB tool...
To find this short pull the listed below items, first. then add MAIN relay first , then all others, 1 by 1, key off. then on.
Rule 1, do no hot swap any ECU or PCM.
I PULL: All are IG loads. key off before removing a part or adding a part , DOME fuse removed to protect ECU)
You don't need to follow my list , this way, you could pull the easy ones first and let reality make the job harder... luck happens, say the fire wall condenser was shorted.
- O2
sensor connector at left side of engine bay fire wall: (a top fail here
or the melted wires near by 2000F exhaust pipe.) (a top fail !
bar none here.)
- Pull the A/T- TCC relay (not found on 5speed cars, ) You may discover that only driving 45mph the IG fuse blows. (stalling motor) that is the TCC path shorted.
- Generator (ALTernator ) rear plug.
- The Ignition coil
COIL (in 1996 16v this HV coil is
inside the dizzy , impossible to pull) so unplugged the Distributor
(Dizzy)
- CONDENSER (on fire
wall above the COIL) It's only a noise filter, it is not the
SUPPRESSOR module.
- Fuel PUMP relay
relay below ECU, or starting in 1996
moved to right side of cab heater box. ( 89/90 has a huge
integrated fuel and main relay, below ECU)
- Main Relay same
loc. next to FP relay ( ditto 96 loc
above) this act kills ECU. The CEL is now out with
this pulled. (I'm only looking for a shorted relay here. coil to
pink)
- The Alarm module. (door /key, belt buzzer)
- Pull C2 connector on the rear of the I/P cluster (a short in speedo head?)
- if the fuse still blows, the harness is shorted and may take a while to find it.
What I do, if the pulled main, kills the shorts, I replace the main, or swap it with the Fuel pump relay (91-98) if the relay proves good, the ECU is shorted, they do so intermittently when the caps dry out.
The 89/90 , has a dual relay, and no separate relay and needs careful attention to what is shorted out. Using and Amp CLAMP here at each wire, makes child's play here. for sure.
The clamp allows me to measure actual ECU current and or fuel pump current directly with ,I might add, NO CUT WIRING. (important that is)
FYI: The pump is a 4 amp load, not 10 , not 15, 4 Amps. Many pumps draw too much current just be for they DIE. (or make huge electrical noise, (seen on a lab scope)
HARNESS BAD:
Do not use an old series connected path Amp meter as a fuse , without this
or you will blow up that ammeter. (shorts can be infinite current)
Some meters are un-fused and just blow up.
This meter, solves all this worry.
Do not short out a fuse socket , ever (using a solid copper or paper clip jumper) you will get a FIRE.
Only use real fuses, or far better, the circuit breaker here.
For sure, if you don't have the ATC circuit breaker tool , shown here, then pulling all loads and plugging them back 1 by 1 starting with MAIN relay saves the most cash in blown up fuses!
You found the IG short (oxygen sensor wires shorted to the hot exhaust, the previous owner felt compelled to remove the wire clamps and let these flop about...
Dangme.
and corrected it !
Bravo !
CASE2:
FI FUSE BLOWS: FI means Fuel Injection, IG means IGNITION.
I will now do the FI fuse blowing tests: at end of this document.
WIRE COLOR BLUE-BLACK has a short,( blue with a black tracer)
Drawing 1: Key on, MAIN closes and the fuse blows, or you hit a speed bump and bam FI blows, Bad ECU IS #1.
If you pull the main rela,y from its socket, the fuse will not blow, but the Engine will never run. (if it does, it's a harness short)
This is a SUZUKI 1.6L 1991-95 ECU 8v only. G16A
Keep in mind all 89-95 ECU loves to short the Blue/black wire. It's a Passion ! No , it's RUBYCON's ghost of the past , and evil ghost. Haunting these years.
I put my AMPcamp meter at the B1 pin wire at ECU actual and it reads 15amps as the fuse blows. or as my CB trips closed then opens.
You need to look up your ECU power pin, the 16v (pre 96) is pin A12, and 1996 is C2-pin12.
If say the ECU pin is not shorted, the we AMPCLAMP (verb) the dizzy wire, blue-black and all other wires of that color to find what load is shorted.
If none are , that means the harness is shorted, and that takes unplugging all harness connectors on the blue-blk feed to isolate which section of harness is shorted and close inspections.
See here for ECU power pins. 1992 to 1995 MPI
THE 92-95 MPI G16B ECU drawing his here.
Below.
The 92-95 power is distributed as follows, The Key Ignition feeds power to the IG-COIL. See it?
Drawing 2: One more common short is the Alternator, at Link A below blowing fuse, below. (the diode pack in the Alternator is shorted)
Drawing 3 :
Now the last drawing on this car , all IG-loads
End IG-coil fuse blows, begin FI blows.
FI Loads: The Black-Red to Blue-black wire feed is shorted to ground.!
The schematic for the 8v FI circuit above seen at Drawing 1:
The 92-95 16v is here. showing all FI loads etc..
The 89/90 is here , now a unified Fuel pump and main relay ! (not the lack of FI fuse and shared IG-coil fuse, see errors I corrected in the drawing.!
To see power feeds to the first OBD2 ECU , the below helps.
The 96 wiring is here. (fuse 7 is main) see the fuse here, moved to the RF fender box.
Fuse #16 IG-coil runs Ignition coil, and other coils in relays and both 02 heaters seen below.
96-98 EFI ECU schematics : Left Middle Right.
More schematics here.
(8v TBI and 16v MPI unified) (see 96+ schematics for FI power routing here)
1991 to 1995: FI fuse BLOWS:
The "FI" Fuse "means fuel injection" it only drives the MAIN relay, (located under ECU next to fuel pump relay, on right side of heater box ,starting in 1996)
So, the short is below this relay, the BLUE-BLACK wire is shorted, and for sure pulling the MAIN relay hides the short, but also prevents finding the short. (relay out)
The best way to find this is to pull all loads, and then add them until the fuse blows, (lacking and ammeter (amp clamp meter) or a Circuit breaker used in place of stock fuse.
If savvy? (tools) attach the AMP-Clamp ,meter to 8V B1 pin or 16v C2-12 key on, see if meter slams over 20 amps and 15amp fuse blows. bingo the ECU is bad. NO guessing here.
In 1989-95 years, the ECU LOVES to short due to BAD CAPS. (ECU is a top fail item for BAD CAPS.)
FI-Fuse blows: (Do not force these locked connectors)
Pulls: Black-blue wires. The amp clamp tried, on every wire ,this color,in the car, finds the path that is shorted, easiest, and fasted, but.....
The below is the pocket full of fuses, way to find the short. (key off , pull item , key on, blows fuse?)
Way1: Left or right, means from the seated drivers perspective.
- Pull the Fuel pump connector , PINK, wire large
behind left
rear tail
lamp ,or the fuel pump relay, see locations of FP relay here.
- Pull the ISC connector, it's a 12ohm (6 below 1991) it
must not have a 0 ohm coil, pull it now. (at TBI right side or on
left lower front side if intake on 16v) (
- Pull All 2 VSV valve conn. in Drawing 1. (usually only 3
VSV on front of motor or front right near evap tank)
- If
16v MPI? pull the MAF sensor connector now. (next to Air
cleaner box, just to the rear of box ,fitted right there) Hacked
up, CAI cars, anywhere.
- Pull all 4
injectors connectors, if engine is 16v now. (do not force any connector
,all conn. have lock levers, extreme car, Suzuki don't sell them ,
the jokers. IMO.
- Pull distributor connector, (it's locked, do not
force
any
connector) and this dizzy never shorts here, but the list must be
accurate and complete. Entropy is cruel.
- I pull the ECU connectors ECU loves to ECU shorted B1 pin due to bad caps. (A TOP
FAIL after 02 shorts) The ECU pins that are FAT , are the ones
that SHORT.
- Pull MAIN relay last, if
pulled too soon , it hides may shorts above, pull main last.
- There is now , nothing connected to the FI feed buss.
so....
- If all loads above are pulled, and she blows fuse FI , the harness is bad, see how to fix that above under harness. using Black-blue wires to test.
This relay is near the group of relays just in front of all A/T opted cars, it has a blue-black wire, bingo. TCC relay.
Way2:
The PULL all list , Key off and pull all things listed above. (saves fuses but is more work)
Then
Key on, boom, fuse blows , its a bad harness or some alarm installer (hacker) modified the harness.
No boom ! (I'll use that slang for now on ,to be brief, for the fuse blew)
Never hot plug any parts key on, (keep the dome fuse out ,until the ECU is installed.)
- Fresh FI fuse. 15amps
- Plug in the MAIN relay first. key on? good,
keyoff
- ECU is next, plug it in, and key on ,
boom? (a top failure here.)
CEL now glows. key off.
- Put back Fuel pump relay or pink wire connector now. key
on, wait 3 seconds, no boom. you heard the fuel pump run for 3
seconds. good. (89/90 plug in pump)
- Plug in all VSV, (these never fail much so just do them all, if the fuse blows, im wrong, try 1 at a time. VSVs are good, keyon.
- Plug in MAF is engine is 16v MPI. (skip for 8v)
- Plug in the Distributor. key on, no boom.
- Plug in all four 16v injectors (skip for 8v) keyon, no blow, and crank motor, no blow?
- Plug in the ISC,key on , and crank , no blow?
- Put back the dome fuses. The short is gone. and car
starts?
Make sure you use CB near the one rate in the failed circuit, a little less is Tokay, but bigger is wrong. All auto stores, in my town have CBs on the Fuse rack !!!
Sources: vast:
The Fuse buddy wins the award.
- Remove the "FI" , ATC
fuse from cab box. (or any fuse load that is shorted) FI is just
and exampe the Fuel Injection fuse.. (could be any fuse)
- Rig up or plug in, a
circuit breaker and connect it to the FI
socket.
- Key on , it blows and keeps resetting, good ,the above works or you must reset it by hand , that's ok too. use any 15-20 amp breaker. DC.
- Pull anything you want , in lists above, but
do not pull the MAIN relay until last. if ECU shorts are suspected (I'd
defeat the Fuel pump first , in
89/90 only the pink wire can kill the pump, no FP relay that year )
- The next pulled device,
this stopped the CB from tripping, so that was the shorted
device. You found it.
The 1989/90 will blow the IG fuse (no FI fuse exists) so pull the Fuel pump pink wire first. (there is no FP relay, pulling main ,kills all paths so you must do main , last)
The 89/90 is here , now a unified Fuelpump and main relay ! (not the lack of FI fuse and shared IG-coil fuse, see errors I corrected in the drawing.!
In 1996+ the ECU changed, but there is a main and and FP relay moved to right side of the heater box. (very rare for 96+ to fail like this)
and they moved the fuses. See here the changes.
Suzuki's have a weak wire gauge feeding the ECU and the shorted fuel pump, likes to make the ECU reset over and over, click ,click ,click.
The pump is 4 AMPS running, if it hits about 10 amps the ECU goes quite MAD! The pump can go bad and become this huge noise generator.
On the O-scope DSO you see HUGE brush noise or shorted fuel pump commutator segment is vivid details on said scope. Love my scope.
Can see about to fail 100% dead pumps, early just buy LOOKing. (amp clamp for scope)
end ECU issues:
CASE #3: The "TAIL" fuse blows (park, tail, running lights and interior dial lights and illumination lights)
EXAMPE #1: (above is ECU issuses)
Blowing the PARK/TAIL/RUNNING light fuse , you are! I like the PARK name, there are tail lamps in the front of car and side, is that not confusing, yes, call them PARK)
In 1920 there were just 1 or 2 tail lamps, things changed. They are parking lamps. (or dusk lamps, in some states)
This FAIL path in most cars, is the most hard to find, due to the vast network of wires on the PARK feed. Up to 20 lamps! Daunting comes to mind....
(I turn the Headlights to park (1st click) and BAM the park fuse blows) Dang me !
The Park -Tail- Running lights are shorted. (this includes all the dash lamps, that are dimmable)
A Great potential here , to short.
(funny how the 2 lamps in the front are called tail lamps?, they are park or running lamps, but are one in the same.) Back in 1920 there was only one tail lamp, but not today.
Each lamp by itself measures a 0 ohm short cold, when the bulb tungsten filament is dead cold, so using and ohmmeter (resistance Rx1) ,you will not find your short, with lamps present.
Imagine 20 lamps connected, all reading in parallel 0 ohms, you get 0 ohms and for 100% sure,this is very normal. (All lamps must come out or use the tool below)
When the lamp warms up the OHMS is 120 ohms for one lamp. R = V/I or as 6 ohms for very powerful brake lamps.
Pure cold tungsten is 0 ohms cold.
You do know these lamps love to short, right? the base gets loose and bam is shorts. (over twisted by Gremlin's?)
1156/1157/s are classic; loves to short and 10x that, if from China crappola If you can not find the short, you may have to pull all the park lamps 2 Front /3 rear. Kinda a first thing first here, as is turn down the dimmer knob on dash.
last? (what I do is pull body harness connectors to Isolate Engine bay side, Dash side or rear of car , to show what sections are shorted)
The FSM documents every inch of this harness, with a schematic and harness lay out drawings and end chapters.
here is no need to guess here, all that is covered in the FSM. (at the end ) $15 used on ebay, for most older cars.
The amp clamp meter makes all this so easy, move the meter to every wire "this color", on park circuits and bam, here is the short.
Side lamps:
The Push-in type (194's?) bulbs found in side maker park lamps, that have no real base caps , never short. (well, you'd really have to work at that ..... )
If the short is now gone?, bad bulbs removed, don't be surprised , this is common. Test them or buy new ones.|
Dah CAB:?
Called "interior illumination"
Does the dash lamp dimmer effect the fuse blowing? if yes, the dash lamps or wires are shorted.
Did you remove the left rear trail light lens, yet and see that hacked in trailer harness connector with many shorts. sure.
Or the 4 corners of car for damage to wires from previous collisions? or Pack Rats, or squirrels,etc. (no limits on critter damage, seen vast)
You found it, a shorted lamp. Dangme.
General practices, ways and means, to find shorts:
To save a fortune in fuses , get one of these.
CB = Circuit breaker.(auto resets !)
You can find all shorted circuits (not harness actual ) just using a CB, you pull lamps until the CB stops popping.
- The parking lamp bulbs can short inside, the tail and front lamps can be twisted too hard and they always short. so remove them, first.
- Next, dim (twist) the dash
lamp dimmer knob, does that stop the
fuse from blowing? yes? then the cab dim lamps feed is
shorted. Ash tray , Cig lighter lamps, and cluster lamps.
- Say the above passes test. (no blow) I insert my CB into the fuse socket that blows and start pulling harness connector all over the car. The FSM shows them all. EG volume 2.
- I find (example)with the rear harness connector in the driver door threshold plate pulled, this connector hidden , pulled, kills my CB overloading. The short is in the rear of the car.
- I
pull the left tail lamp connectors there. and find which path there is
shorted. (if any) OMG the prev. owner has hack job trailer wiring
here. oh so common....
- I can also pull all lamp loads off, but that is near 20 lamps , so on this circuit, I pull connectors in the harness to find the offending harness section first. Then I pull all lamps on that section.
- What you pull and the order , is your call , and your luck what is bad, but do pull the four corner of car lamps first.
- You can in fact pull all loads,
and all connectors in the shorted branch to isolate any short, not a
harness short... the best way to find harness shorts is below.
and test each lamp 1 by 1, using a car battery. (the fuse protects you from burning wires, if the lamp was shorted)
One great tool to use , is the Amazon sold (GREAT PRICE of $25), short finder. (sold at Walmart for $48, almost 2 times more)
This tool may require pulling all bulbs, to find the short in a harness.
The combined current in the park circuit can add up to 8 AMPs. (lamps active total)
The lamp loads will peg this meter, easy. (but not my amp clamp tool)
I use it only for harness shorts.
The Tenma clamp meter (orange) far below works, ever better at 2 times the #25100 cost. $25
This meter 25100 uses a circuit breaker, and keeps resetting over and over with any short circuit, or overload. The meter is just an inductive meter (wireless)
This Ammeter is Bipolar (silver meter), it shows current direction in a very intuitive way, then needle shows the shorted point of any wire.
All this assumes, the loads are removed first to see if they are not shorted .
But the meter works with the loads in place too. Keep in mind that if the lamps (or loads) total amperage is less that 15amps the RED tube circuit break will not trip.
If there is a short, the breaker (red tube) will trip, and if it does, you can find any harness short, or say a load that is attached mid harness. (move the meter until current goes to zero, (meter center = 0 this is the shorted node.)
or?
If you do remove all loads and the CB trips, and the meter shows it's shorted, the harness is shorted and now use the meter to find it, this method requires you to move the meter along the whole harness
path and find where the meter dies. This point is the shorted spot, to ground. (insulation damage, by now is obvious to the person do doing this, test)
There is no current flowing past that point. (due to the short)
This device saves you boxes of fuses, wasted, and all that time fiddling those fuses and frustrations.
The meter nulling out, discovery, saves unwrapping harnesses to find shorts.
If you already own the CB breaker linked above. and the Amp clamp meter 72-7224, there is no need for the below 25100 meter. The below short finder, is for shops with no good inductive ammeters.
See my phantom drain page, for more tests.
The RED cylinder object below is a hidden CB, or circuit breaker. This replaces the blown car fuse.
hint: smash the old fuse and use the tabs remaining to fit the alligator clips on the below Red tube device.
I lab tested this meter, the meter is about 60 AMP (full scale) from center half way up is 30amps.(measured carefully)
The CB on mine (red tube) does not trip until 15amps. All perfect, for the job, in my opinion.
Instructions are here.
The SHORT FINDER:
See Mr. Duane's VIDEO and use this meter to find a difficult short circuit.
You to can build a test circuit, to learn to use meters correctly. (seen in VIDEO)
The above meter and below saves time. (and fists full of hair )
DMM 101?
How to find some of these parts, a FSM really helps but see here for engine, parts etc.
THE TENMA 72-7224 AMP CLAMP (really is the best bang for the buck...0.1 amps to 400amps) $50?
I can measure alternator charge current and starter current easy. (non intrusively) Even rear defroster current.
The Amp Clamp. This
finds shorts easy, like magic, really. It measures the current
magnetically, no wires !!!. More tools are here.
Find Sidekick engine parts
Find TCC shorts
Find dash parts that can short.
Speedo C2 cable (power to I/P cluster is here) (the black-white wire, going in to HERE can short (rare to the max, but can)
Fuel pump feed , fully covered here, ever detail.
Dirt cheap test tools: "NO AMP CLAMP"
This will work too, and if you have a test lamp, I use a trailer light socket/ bulb, that has a 1157 bulb ,it has 2 filaments, one is parking lights other is brake,
Use the 2 amp brake lamp wire socket leads. and the ground wire.
Connect the cheap meter in the 10 or 20 amps mode (special banana plugs there for that)
Then wire the lamp in series with the meter.
This act , limits current to 2 amps
Then put this Combination end to end, connected in place there to the old blow fuse pins F1a and F1b (any order works , red or black.
Test your setup using a 12v battery to makes ure lamp glows and meter shows 2 amps, never connect this meter directly across any battery, in amps mode. (10A,MA or uA)
If this lamp test fails, the meters internal fuse is blown out. (replace it now) and repeat this test)
Next ,connect up to the suspicious car fuse per below wiring scheme.
Lastly, find out what is shorted by pulling loads. (or other fuses)
You can also not use just this lamp (no meter) as a fuse replacement and see gross shorts. But a meter works best.
At walfart for 8 bucks
version 8: 5-14-2014, added more tools and 1 test.