Airconditioning question
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From: Edmonton, AB.
Airconditioning question
This is probably a question for the techs. Yesterday the temperature outside was about +6 C. I was checking some stuff over on my 04 psd and noticed that went I selected A/C my compressor clutch didn't engage. I checked the fuse and connections to make sure there were know problems and there weren't. The A/C clutch doesn't even engage and cycle in defrost mode. I know that on my last truck It engaged regardless of the out side temperature, but that was a 98 model. So I'm wondering on an 04 if there even is a problem because the outside air temp was only +6 celcius. (I don't know what that is in farenheit.) Do these trucks have a safety switch that prevents the compressor clutch from engaging if it's too cold outside or do I have a problem.
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From: Millersville, MD
My guess is that you did not wait for the truck to come up to operating temperature. Let it do that and check again. Just use the defroster selection as the A/C is used to cut down on humidity/moisture.
I'll bet (unless there really IS a problem) that you will see the compressor run then. If you don't, it's time for a trip to the dealer.
I'll bet (unless there really IS a problem) that you will see the compressor run then. If you don't, it's time for a trip to the dealer.
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The truck was warmed up, in fact I had just finished driving accross the city. I'll try it again on defrost and see if it cycles. Do you know how often it should cycle in defrost?
I checked the A/C clutch fuse already and it's OK. I'm hoping it's something simple.
I checked the A/C clutch fuse already and it's OK. I'm hoping it's something simple.
Tuned
Joined: Dec 2006
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From: Shenandoah valley, Va
Originally Posted by conger
This is probably a question for the techs. Yesterday the temperature outside was about +6 C. I was checking some stuff over on my 04 psd and noticed that went I selected A/C my compressor clutch didn't engage. I checked the fuse and connections to make sure there were know problems and there weren't. The A/C clutch doesn't even engage and cycle in defrost mode. I know that on my last truck It engaged regardless of the out side temperature, but that was a 98 model. So I'm wondering on an 04 if there even is a problem because the outside air temp was only +6 celcius. (I don't know what that is in farenheit.) Do these trucks have a safety switch that prevents the compressor clutch from engaging if it's too cold outside or do I have a problem.
9/5x6 =f-32,
10.8 = f-32
10.8+32 =f
f=42.8 6 degrees Celsius= 42.8 degrees Farenheit
I never see a question that I can answer, hope I didn't blow this rare opportunity
Last edited by vatreefarmer; Mar 18, 2007 at 12:44 PM.
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Originally Posted by vatreefarmer
9/5c=f-32 so at 6 celsius:
9/5x6 =f-32,
10.8 = f-32
10.8+32 =f
f=42.8 6 degrees Celsius= 42.8 degrees Farenheit
9/5x6 =f-32,
10.8 = f-32
10.8+32 =f
f=42.8 6 degrees Celsius= 42.8 degrees Farenheit
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From: Edmonton, AB.
Originally Posted by SONNYY13N
If you are low on freon, there should be a pressure switch that will keep the clutch from engaging, thereby stopping the compressor from turning.
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From: Morgan Hill, CA
The pressure of a refrigerant in a closed system varies by the temperature;
There is a pressure switch in the system that will shut off the compressor when the evaporator reaches the low 30°'s F, and won't start it back up until it reaches somewhere in the mid 40°F range. In warmer weather it will cycle on and off, and the evaporator will vary between approx. 35 and 45°F. This is mainly to keep ice from building up on the evap. Also serves to save the compressor from running a long time if the gas leaks out.
Therefore, when your truck is parked in below freezing conditions, the whole truck, including the AC system will get below 32°F (0°C), and the pressure switch will turn off, and not allow the compressor to run. It will not run until the system temp increases to about 45°.
So, to the point, your truck had probably gotten below 0°C overnight, then when you turned on your AC at 6°C which is about 43F, the system had not warmed up enough to turn back on. Also, if your '98 would turn on the compressor at 'any temperature', then it was broken!
I hope this helps.
mike
There is a pressure switch in the system that will shut off the compressor when the evaporator reaches the low 30°'s F, and won't start it back up until it reaches somewhere in the mid 40°F range. In warmer weather it will cycle on and off, and the evaporator will vary between approx. 35 and 45°F. This is mainly to keep ice from building up on the evap. Also serves to save the compressor from running a long time if the gas leaks out.
Therefore, when your truck is parked in below freezing conditions, the whole truck, including the AC system will get below 32°F (0°C), and the pressure switch will turn off, and not allow the compressor to run. It will not run until the system temp increases to about 45°.
So, to the point, your truck had probably gotten below 0°C overnight, then when you turned on your AC at 6°C which is about 43F, the system had not warmed up enough to turn back on. Also, if your '98 would turn on the compressor at 'any temperature', then it was broken!
I hope this helps.
mike
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From: Edmonton, AB.
Would this still hold true if the engine compartment is warm? I was kind of thinking along those lines as well. I'm an electrician by trade an when we work on an A/C system in a rooftop unit, they usually have a thermal switch to protect the compressor in cold weather. What puzzles me is that the compressor in most vehicles cycles to dry the air in defrost mode. However mine isn't doing that either. Wouldn't that point more toward low coolant? I want to eliminate the obvious before I bring it in.
Is there a sight glass for the coolant level? Where is the clutch relay?
Thanks Mike
Is there a sight glass for the coolant level? Where is the clutch relay?
Thanks Mike
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From: Wickenburg, AZ
I'll bet it's low on Freon (R134a these days). There was a TSB out them leaking freon at the compressor shaft seal, I believe.
You check freon with a gauge set. You need a certain amount of pressure in the system for the safety switches to let the compressor start up. You might to be able to get it up high enough with the little cans that have built in charge hoses. Low pressure feed is on top of the receiver near the passenger side firewall under a black threaded cap.
You check freon with a gauge set. You need a certain amount of pressure in the system for the safety switches to let the compressor start up. You might to be able to get it up high enough with the little cans that have built in charge hoses. Low pressure feed is on top of the receiver near the passenger side firewall under a black threaded cap.
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Thanks for the advice. I think I'm going to book it in when I get a chance. It's one of those things I wanted to deal with before the weather gets warm and the A/C shops are full. As luck would have it, I have a little time since it was minus friggin twenty with the wind chill today. Got to love Edmonton. 
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