Odd A/C issue
Thread Starter
Racer
Joined: Oct 2018
Posts: 333
Likes: 86
From: Hope Mills, NC
Odd A/C issue
Okay team here's another one for you. When I first start my 89 during idle the AC does not blow cold. Once I start moving down the road and reach say 40 miles an hour Denny AC will start blow cold and it will remain cold even if I stop and I'm sitting at an idle. It will remain cold until the next time I shut off the car. The next time I start the car is the same thing all over again. I have gone through the FSM and everything seems to be working the way that it's supposed to and I cannot figure out why it is doing this. Any suggestions?
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Is the AC compressor engaged when you first start up?
If you shut down after it's blowing cold and immediately restart does it still blow cold?
How is the fluid pressure in the AC system?
Does the fan come on when you switch On the AC?
If you turn on the AC after fresh startup and let it idle till coolant temp is up will the AC start blowing cold?
If you shut down after it's blowing cold and immediately restart does it still blow cold?
How is the fluid pressure in the AC system?
Does the fan come on when you switch On the AC?
If you turn on the AC after fresh startup and let it idle till coolant temp is up will the AC start blowing cold?
Thread Starter
Racer
Joined: Oct 2018
Posts: 333
Likes: 86
From: Hope Mills, NC
Is the AC compressor engaged when you first start up?
If you shut down after it's blowing cold and immediately restart does it still blow cold?
How is the fluid pressure in the AC system?
Does the fan come on when you switch On the AC?
If you turn on the AC after fresh startup and let it idle till coolant temp is up will the AC start blowing cold?
If you shut down after it's blowing cold and immediately restart does it still blow cold?
How is the fluid pressure in the AC system?
Does the fan come on when you switch On the AC?
If you turn on the AC after fresh startup and let it idle till coolant temp is up will the AC start blowing cold?
2. If I immediately restart it still blows cold.
3. I just filled the system two days ago.
4. The fan does come on when I turn on the A/C.
5. The A/C does not blow cold at idle even after the temp comes up. I let it idle til the temp came up to 197 and still nothing.
It is the electronic climate control and it has been rebuilt. Like I said, it is odd. It won't blow cold until I get the vehicle up to speed. The compressor is engaging at idle but will not blow cold until I start driving at about 40 or so. I'm hoping I just didn't get enough freon into the system.
Melting Slicks
Joined: Feb 2003
Posts: 2,677
Likes: 812
From: Saskatoon Sask.
1. I'm not sure if the compressor engages upon first start up, will have to check on Tuesday.
2. If I immediately restart it still blows cold.
3. I just filled the system two days ago.
4. The fan does come on when I turn on the A/C.
5. The A/C does not blow cold at idle even after the temp comes up. I let it idle til the temp came up to 197 and still nothing.
aIt is the electronic climate control and it has been rebuilt. Like I said, it is odd. It won't blow cold until I get the vehicle up to speed. The compressor is engaging at idle but will not blow cold until I start driving at about 40 or so. I'm hoping I just didn't get enough freon into the system.
2. If I immediately restart it still blows cold.
3. I just filled the system two days ago.
4. The fan does come on when I turn on the A/C.
5. The A/C does not blow cold at idle even after the temp comes up. I let it idle til the temp came up to 197 and still nothing.
aIt is the electronic climate control and it has been rebuilt. Like I said, it is odd. It won't blow cold until I get the vehicle up to speed. The compressor is engaging at idle but will not blow cold until I start driving at about 40 or so. I'm hoping I just didn't get enough freon into the system.
Melting Slicks
Joined: Jan 2014
Posts: 2,192
Likes: 381
From: Lunenburg MA
Did you fill it with R12 or R134a? Was it evacuated first? Assuming it was done right, I'd guess it's either under filled or it's filled with R134 and the old R12 cycling switch isn't kicking in until it get's warm and the pressure rises. If it was R134 it should have been 2 1/2 cans. If it still has the R12 cycling switch, see if it has an adjusting screw between the terminals (most do). If it does, turn it 1/2 turn counter clockwise.
I would think over charging would do the opposite. Stop working when it gets warm and hits the high limit cutout.
I would think over charging would do the opposite. Stop working when it gets warm and hits the high limit cutout.
Safety Car
Joined: Jul 2004
Posts: 3,845
Likes: 30
In my '88, with the "auto a/c" (R-12), when the ac is first turned on while moving or not, the blend doors move to allow the "venting/discharge" of the air in the duct work....This is done as explained by GM, to preventing the fogging up of the windows...
It will be like that for 30-45 seconds after turning air on then, the vacuum blend doors will open/close and the "full cooling" will start....
Also, as previously stated in this thread, if you have a low charge, the higher the RPM's of the engine as well as the actual wind velocity across the condensor (is in front of radiator) will cause the cooling to be "cooler"...Could be slipping belt, clutch, low charge and sometimes even an over-charge...
Start with the simple then, have your refrigerant charged checked...I have also seen partially clogged accumulator tanks and orifice tube(s) as a cause, debris in front of condensor, and leaking vacuum hoses to blend doors (some are electric)....Check to see if your exterior fan is on!...I had this problem a few years back and found my fan was "ka-put!"...
It will be like that for 30-45 seconds after turning air on then, the vacuum blend doors will open/close and the "full cooling" will start....
Also, as previously stated in this thread, if you have a low charge, the higher the RPM's of the engine as well as the actual wind velocity across the condensor (is in front of radiator) will cause the cooling to be "cooler"...Could be slipping belt, clutch, low charge and sometimes even an over-charge...
Start with the simple then, have your refrigerant charged checked...I have also seen partially clogged accumulator tanks and orifice tube(s) as a cause, debris in front of condensor, and leaking vacuum hoses to blend doors (some are electric)....Check to see if your exterior fan is on!...I had this problem a few years back and found my fan was "ka-put!"...
Last edited by Da Mail Man; May 11, 2020 at 06:31 PM.
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Melting Slicks
Joined: Feb 2003
Posts: 2,677
Likes: 812
From: Saskatoon Sask.
Did you fill it with R12 or R134a? Was it evacuated first? Assuming it was done right, I'd guess it's either under filled or it's filled with R134 and the old R12 cycling switch isn't kicking in until it get's warm and the pressure rises. If it was R134 it should have been 2 1/2 cans. If it still has the R12 cycling switch, see if it has an adjusting screw between the terminals (most do). If it does, turn it 1/2 turn counter clockwise.
I would think over charging would do the opposite. Stop working when it gets warm and hits the high limit cutout.
I would think over charging would do the opposite. Stop working when it gets warm and hits the high limit cutout.