a/c not working
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a/c not working
hey everyone I have a problem with my 2000 F250 4x4. The a/c started to go out. At first it would work for about 30min. than slowly go to warm. After a couple of weeks it quit working all together. I have checked the low pressure sensor and that has power but no power to the a/c clutch. System is good on refrigerant and all fuses and relays are good. a/c switch on the dash is working. Does anyone have any suggestions. Thanks for the help.
Hotshot
Joined: Jan 2004
Posts: 19,768
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From: St Louis
You have a PCM-controlled clutch. The series circuit of the cycling and high pressure containment switches serve as an input to the PCM. The PCM, unless operating parameters preclude it, issues a command to energize the A/C clutch relay which, when energized, switches power from BJB F6 to the clutch coil.
The containment switch should be normally closed.
Check the fuse. See if the relay energizes, jumper the low pressure switch,etc...
The containment switch should be normally closed.
Check the fuse. See if the relay energizes, jumper the low pressure switch,etc...
Lead Driver
Joined: Jun 2004
Posts: 6,362
Likes: 593
From: Amarillo, TEXAS!
That sounds undercharged to me.
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Hotshot
Joined: Jan 2004
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From: St Louis
Not at all. A low charge doesn't behave that way.
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Hotshot
Joined: Jan 2004
Posts: 19,768
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From: St Louis
An iced evaporator will not cause a "no power to the clutch" symptom. Iced evaporators are usually cause by a stuck cycling switch and usually manifest as "reduction in airflow that gets humid".
Low refrigerant charge usually commonly shows up as a short-cycling compressor and insufficient cooling up to the point where there isn't enough static pressure to engage the cycling switch, then it goes completely inoperative. I'm taking the OP at his word that the refrigerant is okay although he might want to expand on that since if it doesn't have enough refrigerant, it also won't have power to the coil.
Low refrigerant charge usually commonly shows up as a short-cycling compressor and insufficient cooling up to the point where there isn't enough static pressure to engage the cycling switch, then it goes completely inoperative. I'm taking the OP at his word that the refrigerant is okay although he might want to expand on that since if it doesn't have enough refrigerant, it also won't have power to the coil.
Hotshot
Joined: Jan 2004
Posts: 19,768
Likes: 1,082
From: St Louis
You didn't. The OP said he had no power to the clutch with effectively rules out an iced evaporator which is what I was pointing out.
Now, if the OP comes back an re-states the symptoms, then that opens up a number of options which were ruled out due to his initial descriptions.
Now, if the OP comes back an re-states the symptoms, then that opens up a number of options which were ruled out due to his initial descriptions.
Lead Driver
Joined: Jun 2004
Posts: 6,362
Likes: 593
From: Amarillo, TEXAS!
OK, here's my train of thought on it:
Originally, the OP said the A/C worked, but gradually faded over 30 minutes. To me, that sounds like icing caused by an undercharge condition.
Then the OP said after a couple weeks had elapsed the compressor won't run at all.
If there's a leak, that seems like the logical progression of things; now there's not enough pressure to close the low cutoff switch.
Granted, that's purely conjecture since the OP didn't say what the static pressure in the system is, nor what the pressures were when the system was operating. He did say there's power to the pressure switch, but didn't say whether he'd verified it was making it through it.
So yeah, I agree some more information would be helpful.
Originally, the OP said the A/C worked, but gradually faded over 30 minutes. To me, that sounds like icing caused by an undercharge condition.
Then the OP said after a couple weeks had elapsed the compressor won't run at all.
If there's a leak, that seems like the logical progression of things; now there's not enough pressure to close the low cutoff switch.
Granted, that's purely conjecture since the OP didn't say what the static pressure in the system is, nor what the pressures were when the system was operating. He did say there's power to the pressure switch, but didn't say whether he'd verified it was making it through it.
So yeah, I agree some more information would be helpful.
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