Wits end with a/c problem
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Senior User
Joined: Aug 2009
Posts: 304
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Wits end with a/c problem
This is going to be long winded but here goes. I have a 99 f250 LD 4x4 w/
5.4 l . No a/c clutch lockup. I have current going to the High pressure
switch and the clutch lockup switch. No current to the compressor. I've tried jumping the switch . Doesn't work. The compressor does work because I bypassed the switch's and sent current to the clutch solenoid and it started working. Thought it might be the a/c clutch diode or the pcm diode but I'm not 100 percent sure how to test them. I do have some
vacuum lines cut but I have vacuum going to the one vacuum line that goes through the firewall. I've checked all the fuses also. Help!
5.4 l . No a/c clutch lockup. I have current going to the High pressure
switch and the clutch lockup switch. No current to the compressor. I've tried jumping the switch . Doesn't work. The compressor does work because I bypassed the switch's and sent current to the clutch solenoid and it started working. Thought it might be the a/c clutch diode or the pcm diode but I'm not 100 percent sure how to test them. I do have some
vacuum lines cut but I have vacuum going to the one vacuum line that goes through the firewall. I've checked all the fuses also. Help!
Hotshot
Joined: Jul 2005
Posts: 11,931
Likes: 180
there is also a low pressure switch on the gas (R134).
do you have a pressure gauge for the AC gas pressure? you should ahve about 120 psi with the motor off. when motor starts the AC should start if you maintain over 25 psi gas pressure on the low side. the high side will go up 150-200 psi.
do you have a pressure gauge for the AC gas pressure? you should ahve about 120 psi with the motor off. when motor starts the AC should start if you maintain over 25 psi gas pressure on the low side. the high side will go up 150-200 psi.
Hotshot
Joined: Jan 2004
Posts: 19,760
Likes: 1,079
From: St Louis
The series circuit of CJB F5, the function selector switch, the HPCO switch, and the low pressure cycling switch provide an input to the PCM to enable the compressor operation.
The PCM, under its programming, will then energize the WOT relay (A/C Clutch relay) which supplies power from F5 to the compressor clutch coil via the energized relay's contacts.
The PCM, under its programming, will then energize the WOT relay (A/C Clutch relay) which supplies power from F5 to the compressor clutch coil via the energized relay's contacts.
Posting Guru
Joined: Apr 2003
Posts: 1,903
Likes: 2
From: Wyoming
I feel rather inadequate following these two FTE studs, but here goes;
if you don't have enough R-134, the clutch won't engage. Could be as simple as adding some refrigerant to your A/C. Should have 25-40 psi on low side with the engine and A/C running.
I'm ready for my beatdown now.
if you don't have enough R-134, the clutch won't engage. Could be as simple as adding some refrigerant to your A/C. Should have 25-40 psi on low side with the engine and A/C running.
I'm ready for my beatdown now.
