AC causes car to over heat

bdemat · Jul 15, 2020

Hello, every one, have a 90 mustang GT. Car runs great accept when I run the AC. Going down the road the air gets cool but not cold. When I am at idle, it gets warm and the car starts to over heat. Soon as I go down the road it starts to cool down again, both the temp and the AC. New radiator, water pump, thermostat, fan and fan cluch. I realize it's a airflow problem but the car is almost stock, what's the cure. Also while not running the AC the temp is perfect even at idle.
Any advise would be appreciated.

Adieu · Jul 15, 2020

bdemat said:
Hello, every one, have a 90 mustang GT. Car runs great accept when I run the AC. Going down the road the air gets cool but not cold. When I am at idle, it gets warm and the car starts to over heat. Soon as I go down the road it starts to cool down again, both the temp and the AC. New radiator, water pump, thermostat, fan and fan cluch. I realize it's a airflow problem but the car is almost stock, what's the cure. Also while not running the AC the temp is perfect even at idle.
Any advise would be appreciated.

Check your fan clutch. Drive the car until it's up to operating temperature, shut the car off, pop the hood, and try to turn the fan. If it turns easily, you need a fan clutch. If it has only slight resistance, you need a fan clutch. If it won't turn or is stiff as hell, it's not the fan clutch, you'll need to look elsewhere in the cooling system.

90sickfox · Jul 15, 2020

Do you have a fan shroud ? If not it could be the issue.

General karthief · Jul 15, 2020

Check the air damn under the radiator support, it a plastic piece that runs vertical below the radiator, also there are two pieces, one on each side of the radiator that close off the opening. I would also make sure the condenser in front of the radiator is clean or does not have a bunch of junk between it and the radiator.
What temperature is it getting up to?
Has the ac been worked on recently?

bdemat · Jul 15, 2020

I had it recharged about two yrs ago. The air damns are all intact but I did notice that there is quite a bit of over spray paint on the bottom of the condenser. About two inch high. Think that might have an affect but it just started this week. It runs normally at the lower quarter mark with out the AC. With the AC it got iin between the half and the 3/4 mark before I turn it off . I took the engine idle up and the engine temp started back down.

revhead347 · Jul 15, 2020

Look in your condensor and see if it's all clogged up with schmutz.

Kurt

mikestang63 · Jul 15, 2020

the AC turned on adds more heat into the engine. You say you have a new radiator, fan, fan clutch, etc...
can you feel the air sucking into the condensor good or is it weak... a clogged condensor will cause this.
you can also take a hose and spray out debris caught in the condensor
Make sure there isnt any trash between the condensor and the radiator
Is your AC system in good shape? no clogs and fully charged
stock radiator or aftermarket.. did you get all the air out of it
are you running an overflow and is it working properly
did you put a new radiator cap on it and test it- is it 16lb
You sure you put the belt on right- dont laugh if you have it on the wrong way it will spin the water pump clockwise. the smooth side of the belt goes against the water pump pulley
Check the fan clutch to make sure it is working properly
Is the shroud good- not cracked and up against the radator
are all the air dams in place
The stock clutch fan pulls over 3000 cfm and should be sufficient to keep your car cool

bdemat · Jul 16, 2020

mikestang63 said:
the AC turned on adds more heat into the engine. You say you have a new radiator, fan, fan clutch, etc...
can you feel the air sucking into the condensor good or is it weak... a clogged condensor will cause this.
you can also take a hose and spray out debris caught in the condensor
Make sure there isnt any trash between the condensor and the radiator
Is your AC system in good shape? no clogs and fully charged
stock radiator or aftermarket.. did you get all the air out of it
are you running an overflow and is it working properly
did you put a new radiator cap on it and test it- is it 16lb
You sure you put the belt on right- dont laugh if you have it on the wrong way it will spin the water pump clockwise. the smooth side of the belt goes against the water pump pulley
Check the fan clutch to make sure it is working properly
Is the shroud good- not cracked and up against the radator
are all the air dams in place
The stock clutch fan pulls over 3000 cfm and should be sufficient to keep your car cool
[/QUOT the radiator is new stock from AZ. I will try washing out the condenser and have the AC system checked. Question, how far should the fan be away from the radiator? Mine is 2, 2 1/2 inches away.

General karthief · Jul 16, 2020

You didn't say if there is a shroud.
You need to get a mechanical gauge and install even if it is zip tied to the wiper arm. This way you can tell what your temps are actually reading.

bdemat · Jul 16, 2020

I do have the factory shroud, but they don't sit flush on the radiator. There's about a 1/4 inch gap on both sides all the way down. The fan is about 2 to 2 1/2 inches from the radiator, I am wondering if I should get it closer with a spacer. It's an all stock car I am assuming that it was manufactured that way.

General karthief · Jul 16, 2020

Does the fan sit about half way in the shroud?

bdemat · Jul 16, 2020

No, it's all the way in the shroud

General karthief · Jul 16, 2020

Pics?

bdemat · Jul 17, 2020

General karthief · Jul 17, 2020

Fan looks correct to me

Monkeybutt2000 · Jul 18, 2020

General karthief said:
Fan looks correct to me

IDK man,I just looked at my car,and from the side it's completely covered by the shroud.

General karthief · Jul 18, 2020

Monkeybutt2000 said:
IDK man,I just looked at my car,and from the side it's completely covered by the shroud.

I'm sure there is some tolerance for the fan in the opening of the shroud, as long a most of the blades are in the opening, there is usually just enough of the blade outside to whack a finger.

HoboNC · Jul 18, 2020

Engine hot at idle while watching the fan turn the engine off if the fan keeps spinning you have a bad fan clutch. I like to see them not turn more than a few turns when I turn the engine off...

bdemat · Jul 18, 2020

Monkeybutt2000 said:
IDK man,I just looked at my car,and from the side it's completely covered by the shroud.

So, you think my fan is to far back? Could you do me a favor and measure the distance from the radiator to a fan blade. I would really appreciate it.

General karthief · Jul 18, 2020

bdemat said:
So, you think my fan is to far back? Could you do me a favor and measure the distance from the radiator to a fan blade. I would really appreciate it.

You are over thinking it. Your fan/shroud is just fine.

AC causes car to over heat

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