bd0nalds0n

Recently, I've had a situation where the warning light for my temperature gauge lights up when the needle gets halfway between the two white marks. This is a sporadic issue, there have been times when the light sort of flashes on and off right when I start the car.

I'm virtually certain that the car isn't running hot, due to the fact that it has occurred when the car is cold.

My first instinct is to change the sending unit to see if that solves it, and then tear into the pod/dash/gauge to investigate further if it doesn't.

My question is whether anyone here knows what is the logic that applies to how the central warning system "determines" when an overheat condition exists and when to light up the red light above the gauge as well as the (!).

I would guess that the sending unit sends out variable resistance which drives the gauge depending on the value, and I would've thought that when the resistance eclipses a certain level (or if there's maybe a mechanical switch that's tripped inside the gauge once it passes the upper white mark), then the idiot lights engage.

My experience would lead me to believe that there's not a mechanical switch in the gauge, since the (!) and red light in the gauge will illuminate even when the temp needle is low, but it also puzzles me as to why the central warning system would engage if the resistance from the sending unit isn't high enough to push the gauge needle into the red.

Anyone chased down a similar problem?

Thanks.

AO

I had a similar issue after monkeying with the nitrous system. It is most likely the sending unit itself ot the wires to it. I found my wires to be almost falling apart and very corroded (sp?). I suggest you inspect the wires and clean the connections. If that doesn't work move on to the sensor. My problem has since cleard up.

Tony

Ive installed an aftermarket Autometer gauge and today i saw water temps at 215-220 the needle was appx at the center of the stock guage. If i get a red light at some point i will let you know what temp that occurs at . I was out and about in my car today, running errands in 104F with the AC on...on onad off boost now and then ....no issues so far.

The most missed issue in coolling with this car is the seal in the Tstat housing. I bet yours looks like this?? (TOP)
The bottom pic is the replacement.
For peace of mind nextime you do a coolant flush or somehting, pop the Tstat out and check it.

Adam C

I am getting this exact same thing. Anybody got an opinion?

Same as donaldson - my red light flickers on and off, sometimes even when dead cold. Must be a sender issue. Ideas?

dr bob

Hmmm. Bottom picture looks bigger. Must flow more coolant. [Homer Voice] Need more reactor coolant! [/Homer Voice]

Seriously, a bit of leakage around the radiator (through the back of the thermostat where that seal hangs out) would do a number on engine temps, especially on hot days. Nice pics Tony!

V-Fib

I recently chased down some gauge gremlins to the engine harness plug. The wiring looked great just looking at it. I unplugged it and turned it over only to find deteriorated corroded wiring. I also had corrosion on the pins inside the plug itself. I'm going to finally break down and bite the bullet and get a wiring harness from Carl.

TAREK

Tony,

Have you attained higher temps since then? and what did they correspond to, on the dash gauge? If not, here's an excuse for a few peak hp runs on the g-tech and other data collection gizmo

BTW 104 degrees F when running errands is pretty darn low!!! Did that correspond to below the first white line on the dash gauge?

Also, how do you remove the thermostat inner seal? Mine is being too stubborn and I don't wanna break it into little pieces if I don't have to

TIA

Peter F

When changing my inner seal I had to beat it pretty hard to get it out.
(so much that it deformed)
Nothing to worry about though, just take care not hurting the aluminum seating.

Cheers/Peter

Garth S

When changing mine, I first tried to cut it out with a razor knife - catch one edge with a screwdriver and drive it to the center of the opening: the (uncuttable) metal ring collapses easily: the new one taps in place as any seal does.

TAREK

Thanks guys. So I guess I'll have to remove the water bridge for better leverage

heinrich

Tony, correct. That seal is a great way to solve overheating issues, and is *always* rusty. Brian, there are two circuits for temp, the warning circuit and the gauge circuit, they are independent. If the warning comes on and the gauge looks OK, there is a problem where one is too high or the other is too low.

heinrich

Garth has it. One caveat: DO NOT lever against the opening, it will definitely bend and deform. Insert wood or thick leather if you must, but I just push inward (to the centre of the opening) and it bends fine and then pull it. Takek ... no need to pull the bridge.

worf928

Heirich, I always believed the above to be true until I looked at the wiring diagrams a few days ago. The temp gauge on the GTS acts wacky after several hours of driving and thus I looked at the GTS wiring diagrams. The only coolant temp-related sensor that goes to the pod is the temp sensor on the driver's side of the crossover. I was a bit skeptical. But, I didn't find another sensor.

I'd be grateful if you could reference the wiring diagrams and point out what I missed in my search. Or do you mean that the two circuits are in the pod but are feed from the same signal?

heinrich

Dave that is what I mean, the sender units are shared but the circuit afaik from there are entirely separate.

worf928

Blarg. I was really hoping I was wrong and my original interpretation of your post was correct.

I do not like the idea of a single sensor feeding both the gauge and the idiot light.