I noticed during a trip to the store that the A/C in my F250 was blowing cold at idle, but as soon as I hit the gas the A/C started to blow warm air. As long as the car is at idle or at a stoplight its fine, but as soon as the RPM rises over 1000, the air starts getting warmer as if the compressor is actually going off. I checked the low side pressure and it was at 45psi. The compressor looked as if it was engaged the entire time, on the throttle or not. What in the world would cause this? It seems backwards from what usually goes wrong. Any suggestions would be great! Thanks Wayne
Weird problem with A/C
- Thread starter wayniac
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Compressor clutch slipping?
Maybe a vacuum dump is shutting a door servo?
That's odd, because it normally works in reverse. Normally if you are at idle, the air is warmer because of less flow through the compressor, and when you hit the gas it gets colder. I can't imagine what is wrong, maybe someone else has an idea.
Did you check it while you revved it? Maybe when the RPM goes up it pulls down the low side until it hits the cutoff.
Originally Posted By: willix
Maybe a vacuum dump is shutting a door servo?
x2 vacuum drops and the doors start moving.
Maybe a vacuum dump is shutting a door servo?
x2 vacuum drops and the doors start moving.
I checked it while revving and the compressor looked like it was engaged. If the vac pressure dropped and doors were being moved wouldnt it do it at idle too reason being is its a diesel and they have to generate vacum?? I have no clue, clutch slipping seems like a good idea though,
Could be the coolant shut off valve is not shutting off the flow of hot antifreeze to the heater core. This would allow the hot flow of antifreeze to put more btu's into the air stream when the engine goes up in rpm's as there is more heat in the antifreeze and the vehicles water pump also increases flow with higher rpm's. Some coolant shut-off valves can be seen moving. I know you can see the older GM ones move, but do not know about Fords.
It would not be an easy test, but you could by-pas the heater core and drive the vehicle with AC on to see if it makes a difference.
Check the drive to the heater core shut-off valve vacuum or electric.
Sometimes these valves just get rusted so they will not change position.
It would not be an easy test, but you could by-pas the heater core and drive the vehicle with AC on to see if it makes a difference.
Check the drive to the heater core shut-off valve vacuum or electric.
Sometimes these valves just get rusted so they will not change position.
You need to double check your compressor operation again.
Typical symptoms of a low refrigerant charge.
Typical symptoms of a low refrigerant charge.
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Originally Posted By: wayniac
I checked it while revving and the compressor looked like it was engaged. If the vac pressure dropped and doors were being moved wouldnt it do it at idle too reason being is its a diesel and they have to generate vacuum?? I have no clue, clutch slipping seems like a good idea though,
The older Ford PSDs have a electric vacuum pump. At some point they changed to electric servos to control the various HVAC systems; dont know what year. If the vacuum pump fails though, you lose it all the time, not just off idle..
I could see it slipping, maybe. Is there an excess of clutch dust on or around the compressor?
I checked it while revving and the compressor looked like it was engaged. If the vac pressure dropped and doors were being moved wouldnt it do it at idle too reason being is its a diesel and they have to generate vacuum?? I have no clue, clutch slipping seems like a good idea though,
The older Ford PSDs have a electric vacuum pump. At some point they changed to electric servos to control the various HVAC systems; dont know what year. If the vacuum pump fails though, you lose it all the time, not just off idle..
I could see it slipping, maybe. Is there an excess of clutch dust on or around the compressor?
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I actually topped off the AC a couple of months ago, The charge was sitting pretty on the high side of normal, The charge has not moved since I serviced it last. If there is low coolant wouldnt the compressor cool better if the vehicle is at operating RPM? considering the compressor is engaging... There does not seem to be any discernable dust on or around the AC clutch, however it is on the bottom of the motor.
we had a Ranger in doing the same thing.It was a thin hard plastic vacuum line disconnected near the oil filler.It sounds like a vacuum issue somewhere.
I am about to find out!! this perplexes me and I thought I would let the "experts" handle it, so to speak... I still have some warr. left on the truck, but my last dealer visit made me lose my faith (see general automotive forum). I was trying to take a trip this weekend and use my truck, so we will see what they say. Any opinions are still welcome, and I will let yolu know what they DX.
C'mon guys, this is easy.
Most all AC compressors DISENGAGE when you step on the gas hard! [electronic controls]
This is actually a good thing for power when you need it, but be aware of it.
Most all AC compressors DISENGAGE when you step on the gas hard! [electronic controls]
This is actually a good thing for power when you need it, but be aware of it.
OK THE DIAGNOSIS IS IN... The dealer has spoken... drum roll... Its the Accumulator!!! (and the lines, and o-rings) When I get it fixed, I will have the proof!! (of what i am not sure of...)
Originally Posted By: mechtech2
C'mon guys, this is easy.
Most all AC compressors DISENGAGE when you step on the gas hard! [electronic controls]
This is actually a good thing for power when you need it, but be aware of it.
Thats at about 70% throttle or more. He didnt seem to specify it was only when flooring it.
C'mon guys, this is easy.
Most all AC compressors DISENGAGE when you step on the gas hard! [electronic controls]
This is actually a good thing for power when you need it, but be aware of it.
Thats at about 70% throttle or more. He didnt seem to specify it was only when flooring it.
Originally Posted By: wayniac
OK THE DIAGNOSIS IS IN... The dealer has spoken... drum roll... Its the Accumulator!!! (and the lines, and o-rings) When I get it fixed, I will have the proof!! (of what i am not sure of...)
Stopped up accumulator? Broken dessicant bag?
OK THE DIAGNOSIS IS IN... The dealer has spoken... drum roll... Its the Accumulator!!! (and the lines, and o-rings) When I get it fixed, I will have the proof!! (of what i am not sure of...)
Stopped up accumulator? Broken dessicant bag?
They did not tell me, however I asked why the accumulator would fail and cause this problem, and the tech will get back to me was the reply...
The problem did not occur at full accelerator, anything over 1K to 1.5K RPM and the AC Blows warm air...
The problem did not occur at full accelerator, anything over 1K to 1.5K RPM and the AC Blows warm air...
If they are doing hoses or seals, they are opening up the system so maybe they are replacing the accumulator as part of that.
Actually a blockage of some sort still makes no sense to me, and the accumulator is a 700.00 part to replace.
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