formula1nut

I have a 1999 Coupe with dual zone Auto air. About two years ago (maybe 1500 miles) everything under the hood, AC related, was replaced. When it works the air blows very cold.

The problem that I am trying to resolve is that it stops blowing cold air more or less intermittently. It always runs cold on start up. Generally it continues to run cold for an hour or so. Then it continues to blow air but it is not cold, just air. I can recover the cold air by turning the AC off for 2 minutes then turning the Auto back on. BUT that only lasts cold for 15 minutes or so. Again if I shut it off and back on; the cold comes back on for another 15 minutes or so.

Once it fails it will not run cold in manual mode.

There are no codes.

I have done the reset procedure several times.

Coolant temperature always normal.

I am prepared to replace the door actuators but do not want to invest the time only to find out I still have the problem.

I have researched the forum thoroughly and cannot see my specific issue discussed.

Solutions would be very much appreciated.

73Corvette

Sounds like it's freezing off.... we've had some issues like that when low on freon... when you turn the compressor off it thaws out and then cools again till it freezes off again....then blows a little slower and not as cold...

formula1nut

Thanks. I would far rather replace freon than door actuators!
To clarify though, when I turn it off and restart the AC there is only maybe between 5 and 10 minutes.

Still sound like freon?

Thanks a lot!

Robert Perkins

Yes sounds like the system is freezing up, low freon.

tblu92

Does your car have Long Tube headers ??

formula1nut

Yes it does!

Bill Curlee

You need to figure out if the COMPRESSOR is cutting off or running when this issue is happening.

If the compressor stops rotating, it going to stop blowing cold air! Look at the front of the compressor. You will see a belt driven pulley and a center HUB. In the CENTER is the HUB. When the system is ON and running the center HUB should be spinning. When the system is OFF, the HUB will not be rotating.

There's a red light on the HVAC Control panel. When the system stops blowing cold air, what does the red light do???

IF, the system is low on charge, it can kick off on low suction pressure. The only way to see if that the cause is to put a set of gages on the system and see what they are telling you.

Bill

formula1nut

Thanks Bill. There is no indication on the display control panel when the cold air stops. I have not specifically looked at the compressor when the cold air is off for three reasons: the compressor is virtually brand new, when it fails I am driving so would have to be streetside to look at it, third never thought of it!

Bill Curlee

The reason it would possibly STOP TURNING is :

1. Low Suction Pressure Cut OUT switch.

2. High output pressure

3, Bad electrical connection at the AC Compressor Magnetic clutch.

BC

tblu92

Most often when installing LT headers you will find on the passenger side the A/C coolant line will actually touch or be very close to the exhaust tubes----This will make your A/C refrigerant spike up yo very hot temperatures and the A/C will not work after the engine gets warms-----Most LT header companies will instruct you to "bend" the A/C line further away from the header tubes and maybe even wrap them with heat insulation wrap--The A/C coolant line needs to be at least 1/2 inch away from the header tubes or the tube heat will transfer to the A/C coolant and it will blow hot air

formula1nut

Thanks! I will be checking it tomorrow!
Question though.........If I shut off the AC and turn it back on cold air comes back. I am shutting it off for 2 minutes. Would that be enough time for the line to cool off?

Thanks!

formula1nut

I just checked.

I think you are onto something.

On my car the compressor has been moved lower to accommodate a belt driven supercharger. Its line runs parallel to the right side header. Generally it is about 1 inch away from the header. Probably 80% of the line is wrapped in heat shield wrap. BUT the outlet from the compressor is about 1/2 inch from the header and is not protected.

To give your suggestion more credence it does get very hot under the hood. (car NEVER overheats and runs about 220 degrees)

I imagine that if this is the cause it has been a potential issue since it was modified in 2001; just the previous owner never drove it for more than an hour!

I will report back once I get and install the appropriate heat shield.

formula1nut

Today I installed the heat shield insulation. Next step long drive!

formula1nut

After fitting the heat shielding took the car on a three hour non-stop drive. It is fixed!!!!!!!!!!! A huge thank you! 3 summers of frustration gone and as a minimum hundreds of dollars saved. THANKS A LOT!

Pounder