A/c Problems 1989 Diesel

[jrsbvanes]

My A/C system was only working once in a while, I unplugged the low pressure switch and the clutch would not stay on, I then checked the low pressure and found that it was low so I filled it up to 32 psi which the R12 Can recommended. I was getting alot of cold air from the vents. I turned the A/C unit off and back on and the Clutch would not engage, unplugged the Low Pressure Switch and still nothing. I checked the pressure on the line and it read 76 psi which is normal for clutch off. The next day I started the truck and behold the A/C worked well for about an hour then nothing. A couple hours later after the truck sat, it worked again then when the motor was hot It stopped again.

 

Any Idea's what could be causing this problem???

[Spurshot]

First guess is the clutch gap may be worn too large for reliable clutch engagement. I have that problem right now on my 99 2500. Once a clutch gets a few yrs worth of use, it starts to show wear. The electromagnetic clutch can't pull the plate in after the gap gets too large.

[Spurshot]

[Walk9508]

Unless there is something different with these low pressure switches, if you just unplug it you will not complete the circuit. You would have to jumper the connector out because the switch breaks the circuit on low pressure. You could try and jumper it to see if the compressor will come on.

[Spurshot]

Brian is correct. You need to jump the low pressure switch connector after you have disconnected it. I use a small paperclip. It should engage within seconds after you jump it, with the engine running and all the A/C controls on, cool, max fan, recirc, etc..

 

Given the unreliable operation you're getting, I'll stick with looking at the clutch gap first.

 

With all the above done, engine running, low pressure connector jumped, A/C on, if the clutch doesn't engage, carefully get to the clutch and tap it with a small hammer or such. If it engages, it's most likely the gap or much less likely, a weak magnet.

[jrsbvanes]

Brian is correct. You need to jump the low pressure switch connector after you have disconnected it. I use a small paperclip. It should engage within seconds after you jump it, with the engine running and all the A/C controls on, cool, max fan, recirc, etc..

 

Given the unreliable operation you're getting, I'll stick with looking at the clutch gap first.

 

With all the above done, engine running, low pressure connector jumped, A/C on, if the clutch doesn't engage, carefully get to the clutch and tap it with a small hammer or such. If it engages, it's most likely the gap or much less likely, a weak magnet.

 

Thanks I will try it

[jrsbvanes]

Thanks for your help, you are correct the clutch needs help to engage when the truck has been running for a while, do you know what the gap is supposed to be and is there a way to adjust the gap