Air conditioner overheating my old MKIII

[Igottwormms]

I have wondered about this for a while and hoped someone could shed some light on the subject. I tried to use the search to find something out because I figured others may have had this problem however the search feature always gives me a ton of stuff that has nothing to do with what I am looking for.

Anyway, my old supra had a problem. It was a silver 1988 n/a with 7m-ge motor. I had found out what was causing this problem by trial and error the hard way lol. I drove to visit some friends of mine that live about 5 hours away. The car had been driving pretty well but I had noticed the car's temp went up a bit with the ac on but hadn't been a problem until I drove to visit some friends. My supra overheated about 45 minutes from their home and I got a tow using triple A to their house from where I broke down.


To make a long story short......I found out that with my a/c button depressed but not on, it was causing my car to overheat. Once I pressed the button for the ac to let it out I didn't have the problem again but of course I couldn't use my ac without the car overheating. If the ac was running and the ac button was depressed it would overheat also. I don't have the car anymore and I do not know for sure if it had a bhg or not but I have wondered what had caused the problem.


I have recently bought another 1988 red n/a supra that blows hot air out of the ac, but not sure yet if I have the same problem or not. The furthest I have driven it is about an hour or more. I am sure it doesn't have any coolant and I plan on putting some in soon as the summer heat is a bit much (especially when it rains with the windows rolled up lol). I am also wondering, if I ran around with no coolant in the a/c but had the a/c on would that also cause my engine to overheat? Or should running the a/c have no effect to engine temp?

thanks in advance

Wormms

 

[Nick M]

I don't get it. You have the A/C button depressed but it isn't on?

You needed a radiator, coolaing fan, or maintenance of the two items. Such as dirt on the front that you don't see, or maybe the fan clutch had leaked its viscous fluid. Or maybe even the fan did not turn on. The extra heat comes from the drag of the compresson on the engine. The over heat comes from the cooling system needing repair.

 

[Igottwormms]

The ac button depressed but the control was off. As in low - med - high - off.

the cooling system needing repair? What would need repairing? I just found this thread: http://www.supramania.com/forums/showthread.php?15081-Air-Conditioner-Aux-Fan Would an aux fan or switch suggested in this thread cause the engine to overheat and would that be the culprit that would need repairing?

My old supra had a fan and shroud and fan worked fine.

 

[Nick M]

A fan wouldn't make you overheat. The auxillary fans come on with the A/C or high temps. If the system is off, then the compressor is not running, unless you have custom wiring done incorrectly with the system.

 

[Igottwormms]

I am sure there wasn't any custom wiring but could have definitely have been some faulty wiring. I was thinking that with the ac button depressed but the control being off maybe something was running when it shouldn't be. Even with both the ac and the control on low - med - high it would still overheat. If I had found this forum when I had my last supra maybe I could have done some more research or trouble shooting. Mainly I was being a little cautious with my current supra to make sure the same thing doesn't happen and was wondering if that might be a common problem.

I hope to take my supra out for a little photo shoot to make a little thread in the introductions section. Just got an image shack account recently and uploaded a couple pics but I don't have any decent pics of my supra since I have done a bunch of work to it. I hope to get the pics shortly.

Thanks for the help Nick.

 

[Heavy D]

i had the same problem, i was on the highway, i had to pass this guy around 90mph with the a/c, and when i looked at my temp it started to clime up slowly so i turn the a/c and still kept going up, so i pulled over, i let the car cool for 10 min, and my resivour was shaking and pissing out antifreeze so i started the car and cooled back down and drove home with out the a/c, i do use the a/c a couple of times but hasnt over heated again.

also did you converted your a/c system to r134 from r12?

 

[89nasupra]

Do you have the under engine cover on? The condenser in from the radiator gets hot so you are pulling hot air thru the radiator. Make sure there is not trash between the two and use a good A/C coil cleaner and spray them both down and wash them out very good. Check to make sure the AUX fans are turning on.

 

[zman6127]

mines doing the same... just started not too long ago and i discovered i had 2 hoses leaking. I fixed em and then had no problems on my daily route to work and back home. the other day i took a longer trip with the a/c on and started to notice the temp gauge climb a bit so i turned the heat on and it went down. my coolant in my resivor was alot higher ( i know because i was checking it after every drive to make sure my leak was stopped) i turn the a/c off and rolled the windows down and got home ok but now my coolant level is lower then it was from the start ( maybe it overfilled when it was high and hot). ive done a drain and fill of coolant, tstat, rad cap and replaced the two water hoses on back of head. i even bleed the cooland system for air bubbles. its driving me nuts and it only happens if i drive longer distances then my normal route of say 30 miles round trip to work. if i have to pick my son up or go somewher else before going home the temp gauge rises. MY A/C HAS BEEN CONVERTED

 

[Igottwormms]

I knew I wasn't the only one to have this problem lol. The explanation from Nick wasn't satisfying enough to make me think, "ahhh haa. that's what it was!" I wish I could duplicate the problem with my old car but I am glad I can't currently because my new supra may not have that problem. I am soon going to convert it to 134a. I went to toyota and they had freeze 12 and good thing I had read up about freeze 12 here before telling them to hook me up lol. I guess they want you to come back in with a busted ac system when all the oil stops circulating. $$$

I have no idea about if my old supra had been converted or not. It always blew hot air even with the ac on and I never spent the money to go get it fixed or to have someone diagnose the problem. I might have mentioned something to Supraman here where I live at his place in Jonesborough. (A couple people may know who I am talking about. He has a barn full of supra parts and 8 supras in his driveway lol I took a pic at his place which is now my avatar. It's hard to see but there's a 7MGE in the door and a 7MGTE behind it on engine stands) It's been a while ago since I owned my last supra though so not sure if he ever looked at that problem or not.

Keep us updated zman and tell us if you do something that corrects the problem for good.

 

[Heavy D]

i turned my a/c on today again to try it out, and still no problem, it gets cold, and the temps stayed at operation level. just weird how this becomes a problem. but then i did read about converting that you need to buy a couple of adapters and sensors so that the pump and other parts can last longer and work properly

 

[zman6127]

well i thought when i did my thermostat i had the little hole thats to be up, sideways or down so i got a new gasket and started to do it last nite. the little hole was not facing up but sideways, everything was going good till i broke the top bolt off in the housing...luckily it came out easy. so i got some new bolts and will put back together tonite and see if this was my problem. ill let u guys know.