'96 Sunfire - Cooling

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96_Sunfire

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Hey, I know the topic of cooling has been posted a lot about. In brief all I need to know is if I manually push the A/C button is the radiator fan commanded on regardless of ambient conditions?

No need to read further if you know that answer... :)

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Longer story, hence the question:
I have a Cavalier and Sunfire, both '96 models both with extremely low mileage.
The first to exhibit an issue was the Cavalier, followed a few months later by the Sunfire (recent issue).
Both vehicles have had overheating issues (boil overs, hot hot hot), I have subsequently changed/replaced the following in BOTH vehicles;
  • New Water Pump
  • New Thermostat
  • New Head Gasket (the Sunfire had a massive external leak failure)
  • Cooling system reverse flush & fill (vented according to factory service manual)

Cavalier currently running fine, somewhat elevated temperature on the gauge but normal per se. No real concern.

Sunfire running fine, temperature exactly in the middle of the gauge and I cannot get it to heat up at all. Oddly much lower temp showing than the Cavalier.

Previously in the fall, when I pushed the A/C button on either vehicle with the fan on and set to cold, the radiator fan would be forced on. Right now, neither vehicle will do that. Its COLD here in Canada right now, I'm thinking maybe that circuit monitors the intake air temperature and wont turn the radiator fan on? The A/C clutch doesn't come on either.

To check the fan, I disconnected the coolant temp sensor, the fan will come on (throws a check engine light of course).

Because I cannot get the car to warm up to the point in needs the radiator fan to cool, I was hoping to test it with the A/C button... but it doesn't come on. I thought this was odd as the defrost mode generally kicks on the A/C but that doesn't engage the compressor now either? Too cold in Canada to test this?

I have a factory service manual, it doesn't specify whether the ambient air temperature is an input signal for the A/C system. Does anyone here know?

I have a new coolant temp sensor which I may install in the Sunfire, but I do not believe it is malfunctioning at this time. Car currently runs and drives awesome. Two daughters, two identical cars... they're great cars!

Thanks in advance.
 

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if the ac compressor actually engages the fan will come on in your case it could be the extreme cold. Have you used a AC charge kit with a gauge to determine if your AC system has sufficient gas? To verify exact temperatures you need an IR gun you cannt rely on the dash gauge.
 
Thanks. I do have an IR gun, and charged up the A/C only a few months ago. As an update, once the car warmed up (eventually) both the issues I had with the fan were sorted out. Incidentally, that A/C button will not engage the compressor & fan until the car is sufficiently warmed up (odd). Seems counter-intuitive since the A/C helps the defroster effectiveness. Oh well.

The rest of this is just feedback in case others are searching for cooling info later....

This temp gauge has no graduations to indicate the values, but its running dead center, way lower then is has before. Eventually at idle it will climb enough to engage the radiator fan for a few seconds. I'm certain summer weather conditions will result in different behavior. Both the Cavalier and the Sunfire have temperature gauges that move around more than any other car I've ever driven. Strange system design. IR gun says the cavity near the thermostat seems to be happy around 185 to 190°F... the area around the temp sender sits at 195 to 200°F... all good. Fan will eventually come on once the temperature climbs up a bit.

I did change both the cooling fan relay and the blower relay afterwards as cheap insurance. I'll keep the new temperature sender as a spare for now. Ordered two replacement expansion tank caps. Seems they've updated the caps to 18 psi from 15 psi, no doubt there has been debate about that topic before. I'll run the 18psi orange labelled cap with Dex-Cool and call it good.
 
the fans normally will not come on until you hit the 215 to 225 range.
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Thanks Mel, the cooling fan and sender seems to be operating as designed. Wishing I knew what the root cause of the overheating was in the first place. I can only assume the thermostat failed (I may test the old one). I believe the water pump and head gaskets were victims of the overheating issue as I did not spot any leakage from either of them when I first investigated a few days before the massive gasket leak. It overheated again, and the rest is history.... sorry to see it undergo such a repair, for a 22 year old vehicle with only 75k kilometers (46k miles). Runs great again.
 
Thanks Zim, I'd agree must be monitoring engine temp and/or ambient temp. Definitely won't turn on until either one is satisfied.

Still chasing the cause if the failure, I bench tested the old thermostat side by side with a brand new thermostat. Unfortunately they both operated identically which woudl suggest the old thermostat was okay.

New 18psi expansion tank caps now installed in both cars.

Pontiac is running like brand new, perfecto... hopefully it continues to. These cars are under-rated... they're fun to drive. Way more economical than my '17 Hemi powered RAM ... lol
 
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