94 SL2 Overheat problems....

I've had the car for about a year and wrote a couple times about a problem I
was having with the temp gauge bouncing all over. I thought it was the
thermo - changed that, Radiator - changed that, Fan- working

But something happened on the way to and from the Bills-Jets game yesterday
that got me wondering....

Stuck in traffic after the game and temp gradually got up to near red-line,
so we turned on the heat and it dropped a bit for a minute, then came back
up. It was then that I thought of something that I had read on here about
the fan being on all the time when you throw on the A/C...So I gave it a
shot and the temp shot down in a minute and stayed there until I shut of the
A/C, then started creeping up again. Is there some sensor that tells the
fan to come on when a certain temp is reached? Where is it and is it easy
to have it checked to see if it's working right? If not, how much to
replace?

Thanks

 

There is a coolant temperature sensor - on the block near the top left.

If that fails, sometimes the computer will think that the engine is not as
hot as it is and will not turn the fan on. Turning on the A/C will force the
fan to go on.

Stop by the Saturn dealer, buy the coolant temperature sensor that feeds the
computer (there are two - one is for the gage, one is for the computer).

While you're there, ask the mechanic to show you where it is.

It's an easy fix. Good Luck.

 

Coolant temperature sensors seem to be a common failure item on the Saturn
S-series cars, they can crack and result in false temperature readings to
the ECM. Note that there are often two of them, one for the ECM (2 wires)
and one for the gauge (1 wire) - the ECM one is the one you want to
check/replace.

 

There is a coolant temperature sensor - on the block near the top left.

Actually its on the cylinder head but thats detail is trivial.....

This will often be accompanied by decreased gas mileage and possibly high idle.

The sensor with 2 wires is for the computer, with 1 wire is for the gauge. FYI,
the intake air temp and the coolant temp sensor for the computer is the exact
same part number.

 

Thanks for the info everyone...

I'll try to get to it this weekend as Sunday is usually the only day the car
sits still long enough to work on it...

 

I'll try to get to it this weekend as Sunday is usually the only day the car

Let us know how you make out.

 

In my case, I had a defective ECM and not a bad sensor. My '01 SW2's
temperature gauge would shoot up to the red zone at a cold startup
(and stay there), so we knew it wasn't really overheating.
I could, and did, run the car like this for a month after I paid $45
for a diagnosis.
Then the fuel gauge did the same thing. I decided to spring a new ECM
at that point. It fixed the gauge problem.

r.b.