Hey guys, I'm new to subaru's, usually deal with VW's. Anyways, I've got an 88 gl-10 that runs great. It has the digital readout gauges, and while the A/C is on and running, the temp jumps up to almost red, but as soon as i turn off the a/c, it drops back down to normal almost immediately. Also, after the car is parked for a few minutes then we jump back in it and turn it on, the gauge is back up to almost red or is in the red, but as soon as i start driving it drops back down immediately. So my question is this: what the heck is going on here. It doesn't bubble coolant, doesn't seem any hotter than normal by just intuition. Thanks for the help or any information!

Chris

Does your electric fan come on when your temp gauge is up that high? I'd check into that first. My car acted the same way and it turned out to be a sticky/slow thermostat.

+1 or the fan switch or power isn't good.....

Thanks guys. I'll check the electric fan and see if that's kicking on or not, and the thermostat as well. Probably put a new one in, could use it i think.

Thanks again!

Chris

Those turbo engines are temperamental, if you haven't done it or its been a while that the previous owner doesn't know, the cost of coolant and an OEM subaru thermostat are cheep insurance.

 

The fan advice is good, and also check to see if there is any blockage between the evaporator and the radiator, and if the radiator is corroded, both inside and out.

the fan should come on as soon as you kick the a/c on.

 

+1 on the thermostat. make sure you go OEM with it. the aftermarkets suck and these engines are way too easy to destroy by overheating

Checking out the previous suggestions is a good thing to do but since you state that the temperature drops almost immediately after turning off the AC I suspect there may be something else causing the temperature gauge to change like that. I have seen the same kind of thing on my '88 GL-10 and I think what is causing the temperature display to do that is due to bad grounding in the dash or bad connection to the display. There may be bad grounding in the engine area also. On my car at times I would notice the display change as I turned on things like the blower. The display would change a couple of elements to the hotter side and then go down when the accessory was turned off. Cleaning the ground connections in the dash and engine areas may solve this minor issue.

 

If the water temperature was really as hot as the display indicates it is then it would take a period of time for the temperature to drop back down to normal as the engine cools down. The digital display is a nice deal I think but it has little quirks like this. If you want to prove that the water temp is really ok you could monitor the temperature sensor voltage with a voltmeter and see if it changes readings with the display.

A new radiator can solve a lot of overheating problems.

Plus 2 for what cougar says,you really know it when something overheats sounds much more like an earth problem with the gauge it is easy enough to have some radiator place or decent mechanic check if the gauge is accurate.

I added another fat ground wire from my engine to the frame, right at the thermostat housing, for this same issue. It helped a lot but I still see it occasionally. When my blinker goes I can see the dash lights dim slightly so there is some other bad connection in the dash.

Some dimming of the lights is normal. You could try adding an extra ground between the dash cluster and the chassis to see if that helps. Try cleaning the ground to the radiator and battery to chassis ground also.

Thanks guys! I haven't noticed it actually over heating, just that the gauge says it does, but as soon as I turn off the A/C while I'm driving it drops immediately, or if I start driving after it's been off for a few minutes it drops back to normal. I'll definitely change the thermostat and flush the coolant as well as check and clean all the dash grounds.

Chris