Needs some help with A/C
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Freshman User
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Needs some help with A/C
I have a 91 F-150 5.0 4x4. The A/C hasn't worked since I bought the truck. I got a recharge kit but when I connected it to the fitting it pegged out the gage. So my question is where is the low pressure connection, and if the compressor clutch does not engage is there anything that could be wrong other than needing a new compressor.
Fleet Owner
Joined: Aug 2005
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From: Easton,Ks
Use a test light at the plug at the compressor clutch on the front of the compressor.
Turn on the key and put the A/C fan on high and set it to max cool.
With the clip on a good ground put the point on each of the two wires going into the clutch one at a time. One should light the test light.
If it does not light the test light jump the plug at the low pressure switch and see if it lights now. if still no light you may have a fuse or a wiring/switch problem.
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Turn on the key and put the A/C fan on high and set it to max cool.
With the clip on a good ground put the point on each of the two wires going into the clutch one at a time. One should light the test light.
If it does not light the test light jump the plug at the low pressure switch and see if it lights now. if still no light you may have a fuse or a wiring/switch problem.
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Freshman User
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thanks that sounds easy enough. I know I connected my gage to the right port but why would it peg out the gage. The gage is brand new, so i dont think its broken. Would this happen if there is no charge at all.
Fleet Owner
Joined: Aug 2005
Posts: 23,668
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From: Easton,Ks
Sounds like it is fully charged.
Pressures with the compressor off.
Ambient Air Temp.(F) Low Side Pressure(psi)
(F) (psi)
50- 45
55- 51
60- 57
65- 64
70- 71
75- 78
80- 86
85- 95
90- 104
95- 114
Pressures with the compressor off.
Ambient Air Temp.(F) Low Side Pressure(psi)
(F) (psi)
50- 45
55- 51
60- 57
65- 64
70- 71
75- 78
80- 86
85- 95
90- 104
95- 114
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Freshman User
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So I checked the wiring and low pressure switch and all is well. I was thinking of replacing the compressor clutch. Has anyone ever done this and will I lose any refrigerant if I remove the clutch. Thanks
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Senior User
Joined: Jan 2009
Posts: 318
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From: Brampton, On. Can.
If you have power at the AC clutch plug, with the AC set on high, press on the face of the clutch. If it engages, you have too much air gap in the clutch. There should be about .025" gap.
To close the gap, you remove the center bolt and pull off the face of the clutch. When you pull it off, a small washer might fall out of the center bore. That is a shim washer. You would need a thinner washer to lessen the airgap.
To close the gap, you remove the center bolt and pull off the face of the clutch. When you pull it off, a small washer might fall out of the center bore. That is a shim washer. You would need a thinner washer to lessen the airgap.
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From: Gadsden Purchase
All the system needs is just a few drops of liquid refrigerant
to give those readings at any particular temperature.
See it? :)
And in that case it'd be under charged too.
You have to put the manifold set on there and start it up to
find out what's really going on inside it.
High-side, low-side and vent temperature readings as a minimum.
Alvin in AZ
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I pushed on the face of the compressor clutch and it started turning, however once the clutch is engaged it should start cooling the cab, right? I let it run for about 15 min and no cool air. So do I need to get a gauge with a bigger range and try to recharge it? Does anybody know how much it would run to have the system evacuated?
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Messing around with an A/C unit when you really don't know what you're doing can both be expensive and dangerous. Why not take it to a good garage and let them do it. The compressor will cost them around $250, freon around $25, accumulator around $45 and the orifice tube around $5. With their markup the max you ought to have in it is about $450. It may not cost you that much if it doesn't need a compressor. If you fill it with the freon with the can upside down or you open the wrong gauge at the wrong time, it could easily cost you a whole bunch more in terms of hands and eyes.
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Just want to say thanks for everyones help. Im gonna take gopedals advice and let a professional take care of it. I dont know enough about this part of the truck to really mess with it. Thanks again to everyone.