Need help w/ 04 SD AC problem
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Need help w/ 04 SD AC problem
I tried the search function, but did not get any hit that appeared revelant.
The truck is a 2004 F250, in XLT trim, PSD motor, w/ about 70k. miles. The AC is not working. Fuse @ panel is good & the freon charge is good, well w/in limits but the AC clutch will not engage when the controls are in the AC, Max AC, or Defrost mode. The other thing I have noticed is that the normal "thunk" noise of the vent door w/in the dash is no longer heard @ start up. All other controls appears to be working fine, all vents go active & heat goes up & down, but the Compresor will not kick in.
I am suspecting a switch problem of some sort, possibly a vacuum problem. Any help before I go into the dash this weekend would sure be appreciated. Rob.
The truck is a 2004 F250, in XLT trim, PSD motor, w/ about 70k. miles. The AC is not working. Fuse @ panel is good & the freon charge is good, well w/in limits but the AC clutch will not engage when the controls are in the AC, Max AC, or Defrost mode. The other thing I have noticed is that the normal "thunk" noise of the vent door w/in the dash is no longer heard @ start up. All other controls appears to be working fine, all vents go active & heat goes up & down, but the Compresor will not kick in.
I am suspecting a switch problem of some sort, possibly a vacuum problem. Any help before I go into the dash this weekend would sure be appreciated. Rob.
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If the mode doors are not working check vacuum to the heater core/evap core. As for the AC clutch no kicking in and the fuse and freon being good: you need to check the electrical diagram. The high pressure or low pressure cut out switches could be bad which would keep the clutch from engaging.
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From: Edmonton, AB.
How do you know the refrigerant charge is correct? Mine had the same symptoms and my refrigerant was down to 4oz. Should be 2lbs 10 ozs. My buddy is a refrigeration mechanic and checked it for me. Then he recharged the system. It worked for a while, but was losing coolant. Turns out it was a leaking shrader valve and some bad seals around the dryer. I had my dealer repair it for about $300.00, been great ever since. Now here's the bad news... There's a TSB on the compressor for a bad front seal. Apparently the there's a problem with some compressors having a badly machined shaft and it chews up the seal. If you've got one of these, your looking at a new compressor for about $1200.00. My truck only has about 50k on it so I was just off warranty. My dealer said that FMC might pony up for some of the repair cost if it was the compressor. It would probably only cost you an hours labour to find out. Might be a way to go. 
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Set of gages & a good friend who is an experience marine AC mechanic. Enough charge was there so that we should have been at least short cycling. But we were not able to get the compressor clutch to pull in.
A quick circuit check (but not my multi meter) indicated that 12vdc was not getting to the clutch &/or the cutout switches. This combined with the mode (heater/evap. core) door not cycling (the thunk noise) lead me to intially suspect a switch issue. I noticed the 2 systomes @ the same time.
After thinking about it for a bit, rechecking all the fuses, & asking a few questions, I am beginning to think that the 2 sysptoms (mode door & AC cluth not engaging are not related, but are 2 seperate problems (1. A vacuum leak on the mode door & 2. A DC circuit issue) which I just happened to notice at the same time.
Thanks for the info on the seals. I will pay attention to the charge & those areas asa I go back into this weekend. I am hoping to avoid a trip to a shop, in part because of the grief of rides to & from. I give it a bit more trouble shooting time first. Rob
A quick circuit check (but not my multi meter) indicated that 12vdc was not getting to the clutch &/or the cutout switches. This combined with the mode (heater/evap. core) door not cycling (the thunk noise) lead me to intially suspect a switch issue. I noticed the 2 systomes @ the same time.
After thinking about it for a bit, rechecking all the fuses, & asking a few questions, I am beginning to think that the 2 sysptoms (mode door & AC cluth not engaging are not related, but are 2 seperate problems (1. A vacuum leak on the mode door & 2. A DC circuit issue) which I just happened to notice at the same time.
Thanks for the info on the seals. I will pay attention to the charge & those areas asa I go back into this weekend. I am hoping to avoid a trip to a shop, in part because of the grief of rides to & from. I give it a bit more trouble shooting time first. Rob
Last edited by Rob S.; May 17, 2007 at 08:02 AM.
I would hate to have to sit in traffic with no A/C on a hot summer day.
