Got my A/C fixed after many years of not working. Now when I turn it on the A/C the car wants to overheat . 91 Corvette 383 stroker.

 

How hot does it get?

 

The condenser puts out heat and raises the air temperature of the air going into the radiator. You never had this condition before and your cooling system might be on the verge of just keeping it cool without the A/C on.Now that you have A/C, conditions have changed and you might need a bigger radiator.
Try leaving the A/C off and see if things return back to where they were before.

 

What kind of cooling setup do you have? I'd start with making sure the radiator is clean

 

Temp runs 200 or better then I turn it off. With the A/C off it runs fine about 180 or so. I will do some cleaning and see what happens.

 

200 is not unreasonable. Clean the space between the condenser and radiator, blow or rinse out the radiator fins to insure they're clean plus insure the secondary fan is running when the a/c is turned on.

I suspect you don't have a problem, but these are all basic maintenance items anyway so it never hurts.

 

WHALEPIROT is absolutely right! If you have driven one of these cars in Washington DC traffic with the A/C on in August you would see temps hovering in the low 220's when my fans are running. They do run hot but that is what was supposed to make them run so very clean, emissions-wise, that is.

Having worked on several cars A/C systems I do one thing that most mechanics that work on A/C systems don't do. I use "Coil Cleaner" spray made for use on Home A/C systems. One of the first things they do at home a/c service calls is clean the condenser. They frequently have refillable spray bottle and coat every inch of aluminum on the tubes and fins with it. Wait about 5 minutes and wash off with a hose and you are done. Our C4's are old enough that by now if you still have the original condenser on your car there is very likely a big layer of surface corrosion on that aluminum.

Coil Cleaner removes most all of the corrosion and leaves your condenser feeling nice and clean and ready to transfer more heat. I do it as a precautionary thing on all my cars as well as the big condenser outside that runs constantly in August. It takes a very fine layer of corrosion and your condenser looses efficiency fast. Aluminum is a beautiful metal and when welding it I use a spray that removes the corrosion leaving me bare aluminum for a minute or two. This spray is made of the same stuff used in most Coil Cleaners. It is a mild phosphoric acid they use and it works great in either form. Locally I find it at Home Depot or Lowes, just look for "Coil Cleaner" for an air conditioning system.

Since I have a hot running engine in my C3 I use it on Aluminum radiators and their fins as well. I buy the liquid you spray at Eastwood in their welding section. You can probably buy it locally at a welding supply shop.

One last thing, check your radiator hoses and be sure that one or the other is not collapsing under load. The other would be to make sure that you have the proper coolant ratio for your region. Too much coolant and you loose the heat transfer that you need. Here in Virginia I use 30% anti freeze-70% distilled water, this alone really makes a difference.

Good Luck!

 

CT do you take the condensor off the car first? Or just spray it on while on the car? Is it possibly to over-apply and damage the condensor?

Great advice and I'll go ahead and pile on saying that is not overheating. Cleaning the radiator is a good idea but that's not even really that hot. 230+ I would start to be concerned, before that you're fine. The car was designed to run AT MINIMUM at 195 degrees, so anything less than that is under the temp the engineers designed for and 200 is pretty much right on spec.

 

Great post! Thanks guys! My 1990 L98 ran up to about 220 one day last week while slow driving in traffic. I'm in Virginia too and it was hot out and very humid. Once I got out of the city and out on the open road she cooled back down to normal. Coolant levels are fine, no leaks, but I haven't had a chance to see how clean the radiator is yet. I was not aware that had a tendency to run a little hot. Very informative post!

 

Thanks for all of the information , i have work to do . I have never cleaned the radiator or the condenser. Again Thanks