My 90 runs too hot with the AC on?

[drdave]

I live in north Texas, and it is HOT right now. When I have my AC on, and am at an idle or stop and go traffic, my 90 wants to overheat. If I turn off the AC the temperature quickly returns to normal. If the car is in motion, the temperature stays good as well. The problem is only related to the AC being on and the car not moving.

The fan works well, in fact I replaced it a couple of weeks ago. My compressor does not cycle when at idle, may have to do with 134a. Does the AC cycling help to keep the temperature down at idle?

Please help. You only have to idle with the AC off for about 30 seconds when it's 98 outside before you're pretty damned hot!

 

[jymwhi]

DAve,

It was hot here in Portland OR yesterday. I was in some stop and go traffic when I going home and noticed my temp gage was up to the "N" and my AC wasn't on. I got on the free-way and everything was fine, back down to the "L". I also have a new water pump, thermostat and radiator. My guess it is a combo of the hot weather and these "tiny" cooling systems it seems that most cars have now

 

[1stGenSHO]

There is something wrong with your cooling system.
I run around Phx,Az in my '90 and do not have problems. I'm still running R12 for the A/C, but I don't think that would make a difference.
If the fan is running ok, it's probably the radiator or thermostat. Good luck.
1stGenSHO

 

[drdave]

I don't see how it can be my cooling system since my temperature is perfect with the AC off. On the highway the temp stays at A. When in traffic or idling the fan turns on when the needle hits the top of the M and turns off when it hits the bottom of the M.

With the AC on the temp stays in the A on the highway but will try to overheat in traffic or while idling. The only variable is the AC. Now I think the AC cycles at speeds over 30, but does not cycle at idle. I still wonder what the relationship is.

 

[AutoSHO]

The AC cycles based on the refridgerant temperature, it has nothing to do with speed. When it reaches a set cold temp, the compressor cycles off, and then clicks back on when the refridgerant heats up a little.

 

[aberdeenSHO]

I actually just had the same problem... I took it to a shop thinking it was just my cooling system(even though i had replaced everything possible) and found out that it was the head gasket. My symptoms were that the car would get up pretty hot and the fan would kick in moving it back down to the middle in hot weather, but it would never totally overheat without the a/c. When i turned on the a/c, it would completely overheat slowly. Good luck and i hope that's not your problem but it sounds pretty close to what happened to me...

 

[pete c]

how old is your rad? Sounds like it's lost some of it's heat dissipation ability, from years of crud collecting in the fins. It no longer has the ability to keep things cool on a hot day at idle w/ac on, which is the time your cooling system is working it's hardest. You may try flushing the rad or replacing it altogether.