Water Tem. Meter / Gauge Unit testing. 
New sender and STAT, 1991 Kick

Rule 1: It is not an instrument , it has no numbers, the above shows my Photoshop reading with a new sender.
It's only 2 purposes is to warn of too hot, and slow thermostats. (or a frigid engine or cab heater)
Get an IR pyro gun (they are cheap) to find the truth.

The circuit is simple: (just  3 parts, sender, wire , gauge, same as in 1920 cars.)
The ignition feeds 12vdc to the Gauge , the other side of the Temperature guage goes to the sender and the body of the sender is grounded.
Simple to a fault.
It uses lots of current and is way too sensative to bad resistive connections.  (and is slow to react , 1 or 2 minutes to go stable or less)

Meter Test. (fast)
Pre checks (noob levels)  we do not rip the dash apart until last, ok? Only when the meter is known bad.
Key on:
Motor cold , meter at maximum?   fail 1
Unplug the 1 pin Gage sender near thermostat housing.
Did the meter drop to zero. Yes? then is a bad sender. (buy a new sender) if the meter stayed high, the meter is bad, or that wire, your touching, is grounded out.
Motor hot, meter at minimum?  fail 2
Just put a lamp, at the sender pin and other lamp ot lead to ground (use clean metal on engine)
 The lamp prevents damage to the expensive meter. (hard to find too) grin.
Did the meter go near full? yes, meter good, sender bad. No?, meter did not max out, then its a bad meter, replace meter (or the wire is cut ,end to end)
(oop's Suz dont sell meters now.....any more.)

FSM, all tests: (factory service manual)
  • Connnect a 12vdc 3.4 watt  #194 test lamp to the  Yellow/white wire , pulled from sender single pin, at the thermostat housing base.
  • Connect the other end of the test lamp GE #194,  to ground.   ( I converted Japan lamp spec.s to USA lamp numbers) 194 is a sidekick fender side, parking lamp .
  • Turn on the igniton key ( not starting)
  • The lamp will glow and the TEMP needle will deflect slowly up range. (towards H , HOT) The FSM does not say how far. Mine goes fully. It must just go well high.
  • If not, the guage or wiring is faulty at or to  the guage, or the fuse powering the guage, is blown.
Sender test: (Fsm way , in details)
  • Remove the sender itself  (it has 1 pin). (ECT has 2 pins )  This sender is below the thermostat housing.(see location here)
  • Put it into a pan of  water.
  • Attach an ohmmeter to the pin lug and ground of the brass casing.
  • heat water per below.
  • at 122║ deg. F, the Ohm meter will read, 134 to 179 ohms.
  • at 176║ deg F, the meter will read 48 to 57 ohms
  • at 212║ deg F, the meter will read 26 to 29 ohms.
  • if any reading is off, the sender is faulty, if it glitches during the test , it is again , bad.
You can attach an Ohm meter to the sender and varify it  reads in spec. and if it varies.  (meter from ground (-) to tip lug (+) of sender)
If it varies?, then you have one of the problems stated in the last paragraphs below.  Normal is about 40 ohms hot motor. 180║degree F, or up to 195║F.

The Test lamp:

Any GE/CM  #1895 bayonet twist lock lamp
or a #194 car trim lamp works. 
he latter lamp, is very common (as nails in USA)  Remove a car fender trim lamp, ? and use that if no standard test lamp in you tool box.
Do not use tail lamps, they draw too much current.  tail lamp number are 1156  and 1157.
Any lamp at about 1/4amp (0.25) is perfect.  12vdc.   use the fender side lamps or any of the shelf ,AUTO STORE 12v passive TEST LAMP.
(3.4w lamp  Jap. spec,means a USA GE #194)  In Japan they don't use USA lamp numbers, only volts. watts and Lumen's

Do not ground out the Yell/white wire at the sender or the meter WILL be damaged.  ( old school 1960 tactics, can wreck even a simple guage.)
The old Suzuki books tell you to ground it but all newer books show using a lamp test.  (that is because if you leave it grounded, too long, the meter my get damaged , overheated!)

Why are we here?
If you are here because the gauge reads funny ( its not calibrated and has no scale at all , see ?)
If it deflects to any mid scale reading it is working.
If it moves up and down as you drive  then consider the following issues before condeming this simple device.
Guage varies alot ,problem:  (you =someone, anyone)
  • You put in the thermostat in upside down.  The wax pellet end goes DOWN. 
  • You put  the wrong gasket on the thermostat, read the TSB on that issue.
  • There is a water pocket (bubble) under the STAT, because you did not place the STAT bleed hole (jiggle-pin) forward, this bleeds air off the water jackets.
  • The Clutch fan is siezed or dead (slips full time). See fan test links here.
  • Fan Belt is slipping.  Tighten Alternator mount.
  • Bad thermosat (sticking inside )  New STAT time.  (slow stat,  stuck open , or close or not opening fully hot.)
  • Corroded Temp. Senser (gauge only) the lug  pin (faston) can get loose causing the guage to go nuts, but not the EFI, it has its own sensor ECT.
  • Its -10║ F outside  (TOO COLD) and you forgot to put cardboard on the front of the radiator ( watch the truckers, copy them) [start with 1/2 blocked]
  • Bad Guage, wiring to it or bad power feed to it. 
If your thermostat housing has a 4mm rim (not 1mm) IT must HAVE the rubber surround gasket on the STAT itself and NO paper gasket at all.!
Or the STAT will float around and make coolant temperatures, vary like crazy.  << A.K.A: the frigid  Kick syndrome
Aka = also known as,......

When the thermostat is floating , the water (coolant) walks around the STAT, (illegal bypassing it) and this causes , cold coolant, and ECU that goes totally nuts.
The ECU just HATES this, and you EFI will suck fuel like NO TOMORROW !!!
The better condition the radiator is, the worse the Frigid.

Read the TSB and use the correct parts.
The Factory Thermostat comes with both gaskets,  so is not a problem.  SEE ?  NOT A PROBLEM with TSB and FACTORY THERMSTAT KIT in hand.
The Stupid aftermaket , comes with the wrong gasket or none at alll,  so buy both gaskets before doing the job. Splurge and blow extra $2?

ver4  12-22-2012