What could possibly cause this to happen. I drove 4 hours from Toronto to Windsor yesterday in the blazing heat. I dont know why this happened but My temp rose almost o max after having the A/C on for more than 5 minutes.

Anyone know why ?
Any fixes?

Your thermostat is probably bad, pull it out and check it. The car does work harder when the AC is on and does tend to get a bit hotter, but shouldnt goto max temp. Does this only happen when the AC is on? Also check the cooling fans, make sure they are coming on when under load.....just two cents from this monkey....

I'm 99% sure that what Yahnozha said will correct your problem, but...

You didn't mention how efficiently the A/C functioned during this 'heated episode'. If, after following Yahnozha's excellent advice, you still find a problem, your A/C compressor might have started seizing-up. On a 10 year old car, it's worth checking it out.

An additional comment here (hoping not to sound too preachy) but...

If a member finds that their car suddenly starts to overheat (for no obvious reason – like low oil pressure etc), DO NOT switch the engine off. Put the heater on full and pull to the side of the road – and leave the engine running, unless the temp continues to rise. Only switch-off the ignition when the temp get back to something approaching normal.

Originally posted by Gaz
I'm 99% sure that what Yahnozha said will correct your problem, but...

You didn't mention how efficiently the A/C functioned during this 'heated episode'. If, after following Yahnozha's excellent advice, you still find a problem, your A/C compressor might have started seizing-up. On a 10 year old car, it's worth checking it out.

An additional comment here (hoping not to sound too preachy) but...

If a member finds that their car suddenly starts to overheat (for no obvious reason – like low oil pressure etc), DO NOT switch the engine off. Put the heater on full and pull to the side of the road – and leave the engine running, unless the temp continues to rise. Only switch-off the ignition when the temp get back to something approaching normal.

My first impression of things is to check your fans, relays, etc. I doubt it's the compressor cuz the A/C seems to be working just fine, and a compressor is unlikely to affect your engine at all. Also try checking things like coolant and such like that.

Here's the scoop. A/C works but not 100%. Its better than keeping the window open but is not really cold. When I switch the A/C on I get a sound from the compressor area which sounds like someone blowing over an empty beer bottle. the A/C works but its not really efficient nor is it cold.


I think I will definately need a recharge. How do I know I need one and that it is not something else?

Thermostat is fine when A/C is not on but if Im on the highway in excessive heat then we have a problem. Only in extreme heat + A/C does the temp. gauge rise to 90%

Originally posted by GTA_G20
Thermostat is fine when A/C is not on but if Im on the highway in excessive heat then we have a problem. Only in extreme heat + A/C does the temp. gauge rise to 90%

That still doesnt mean that your thermostat is working properly. Take it out and throw it into a pot of hot water and see if it opens. If it doesnt get a new one...

Another thing you may want to do if you havent done it in a while, is to flush your coolant system. That will help loads, no telling what is in there...

If you only experience this overheating when the A/C is on then, and everything else has checked-out okay (see Yahnozah and FF Drifter above) my bet is that the problem is likely the compressor starting to seize.

Despite what FF Drifter said, you have only to switch on the A/C on most G20's to notice the increased engine load – and that's with a perfect A/C system. This load is due to the power required to drive the compressor. If the compressor starts to seize (bind), the load will be increased that much more.

The early warning is poor A/C, the late warning is overheating because of the extra power required to provide the increased torque necessary to turn a compressor with bad bearings. If the belts are properly tensioned, the final warning is the belt starting to burn and smoke because the compressor has seized.

If all else fails, I would have someone check the compressor. Although a lack of coolant gas could account for the inefficiency of the A/C system and cause the compressor to run excessively, that alone should not cause the engine to overheat on such a short trip. I would put my money on fried compressor bearings!

I did notice the temp rise quiker and hotter on the G20 when driving in the Nevada/Arizona/Utah desert and would sometimes turn off the A/C for a few minutes to let it cool down.. It never got that close to overheat though.. just past the normal operating tempature I was used to seeing and since I was still far from home, I choose to live without AC every so often to allow the car to cool down...

How fast were you driving to Toronto? Mybe that has something to do with it too? -- grin --

I was doing about 80-90 miles an hour for four hours. It was so hot outside I took my shirt off and had the windows open and I was still sweating. The A/C would only last for literally 3minutes before I had to turn on the heat to let the heat out of the cooling system

Originally posted by Yahnozha
Your thermostat is probably bad, pull it out and check it. The car does work harder when the AC is on and does tend to get a bit hotter, but shouldnt goto max temp. Does this only happen when the AC is on? Also check the cooling fans, make sure they are coming on when under load.....just two cents from this monkey....
I have to agree with Yahnozha on that:the only factors that could contribute to the temp gauge rising is a bad thermostat and cooling fans not working. I can't see anything else that would have such an effect.:-\

i had the same problem and now i need a new engine............the problem a bad radiator, i know it seems wierd but trust me mine was doing the same thing so i stoped using my ac and then when the temp started to rise outside it would start doing it agian. i changed the thermostat to see if that was the problem and no about aweek later my car overheated---it went past the H on the gauge and i warped the block..........SO GO GET IT FIXED ASAP---A FEW HUNDRED DOLLARS IS A LOT BETTER THEN $5K FOR A NEW ENGINE

Originally posted by P10 WRC
i had the same problem and now i need a new engine............the problem a bad radiator, i know it seems wierd but trust me mine was doing the same thing so i stoped using my ac and then when the temp started to rise outside it would start doing it agian. i changed the thermostat to see if that was the problem and no about aweek later my car overheated---it went past the H on the gauge and i warped the block..........SO GO GET IT FIXED ASAP---A FEW HUNDRED DOLLARS IS A LOT BETTER THEN $5K FOR A NEW ENGINE
:surprised Bad radiator? What happened to it?:-\