A/C compressor not cycling on

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1998_K1500_Sub

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OK, looked at the pictures.

Looks like some leakage around the input shaft.

Some is splatter visible around this side, but it's not a shower of oil. Might it just be "legacy oil spray" from when someone attached / removed the A/C hose from the high-pressure fitting? That would be my guess (which is why, when I'm working on AC, I usually clean-up with a shot of Brakleen around the fittings and nearby, to remove the oil splatter).

All-in-all, doesn't look like a mess (to me). Looks like a slow leak, IMHO. A big, fast leak would have left a bigger mess. That's good... it means it didn't spray a lot of oil about, which would make it more difficult to restore the correct oil charge in the system because you wouldn't have any idea how much was lost. With a slow leak, you don't loose much oil so, during the fix, you can add (say) 1Oz to make up for the oil loss due to leakage and call it good.

The R4s were notable for leakage around the input shaft and the case where it meets the back of the compressor (there's an O-ring there). You can re-seal it yourself if you're ambitious; there's parts available and instructions on YouTube.

If you pull the orifice tube and find the screen clean, and the oil clear (except for dye), you're in great shape. Fix the compressor, new drier, restore the oil balance, vacuum it down overnight...
 
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1998_K1500_Sub

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Here are two pics in the dark with UV. The back of the compressor is clean.

Hey, check me on this... Is there some dye on the backside of the fan blades? In one of the pictures there appears to be. If so, I would investigate a possible leak in the condenser; pull off the upper-half of the radiator shroud and look around with the UV light, see what you find.
 

K-Man

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Hey, check me on this... Is there some dye on the backside of the fan blades? In one of the pictures there appears to be. If so, I would investigate a possible leak in the condenser; pull off the upper-half of the radiator shroud and look around with the UV light, see what you find.
When I had the A/C rebuilt 4 years ago, the shop installed new condenser up front because it had leaked, so should be good but I'll check. The more I think about it, the more I believe it is a slow leak. It seems to me that every time I have looked at the compressor since last summer I have noticed more and more chalky white buildup on and around it. Where is the input shaft? Also, I put a gauge on the low pressure side and it is reading low, but still the needle did move half way to the green...
 

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I see, the input shaft is the drive shaft/pulley. So the old compressor is salvageable if it is an input shaft o-ring leak?
 

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If I just end up replacing the compressor, which one should I buy? I think I bought this one from NAPA. Are there any other parts/ o-rings I should replace while I'm in there? 1998, I see that you mentioned the Dryer and clean the orifice tube, Thanks!
 

1998_K1500_Sub

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I see, the input shaft is the drive shaft/pulley. So the old compressor is salvageable if it is an input shaft o-ring leak?

If that compressor was quiet (didn’t sound like a rattling paint can) when in operation, I encourage you to keep it. Too, if there’s no evidence of leakage around the rear of the compressor, then that rear O-ring is still sealing… that’s good.

If you’re a DIY kind of guy, the shaft seal can be done as follows (what’s shown is more extensive than just the shaft seal, but it’s all interesting):


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Otherwise, ask around and see if some shop will help you replace it.

A quiet R4 is a thing of beauty.
 
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1998_K1500_Sub

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If I just end up replacing the compressor, which one should I buy? I think I bought this one from NAPA. Are there any other parts/ o-rings I should replace while I'm in there? 1998, I see that you mentioned the Dryer and clean the orifice tube, Thanks!

Pull the orifice tube first. If it’s clean and the oil’s free of debris, good. If there’s debris then we need to reconsider your options because there’s much more work necessary.

Assuming it’s clean, get a replacement receiver / drier, some appropriate PAG (the viscosity is likely listed on a sticker underhood… look for PAG46 or PAG100 or PAG150), a new orifice tube doesn’t hurt but you could reuse, new seals for the compressor outlet & inlet. A complete “seal kit” would be handy and is only a few $.

What did I miss?

If you want to charge it yourself, say so. People here can guide you. R134a. Gauge set. Vacuum pump and oil.
 
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I just noticed today that my A/C ‘94 350 is blowing hot and compressor is not cycling on. It seemed to just stop blowing cold. After a little research I tried bypassing the cycling switch with a jumper and compressor kicked in. Thought it was the cycling switch so bought a new one and same problem. Is there anything else that controls the compressor engage? Can low Freon cause it not to cycle? Should it cycle no matter what? Is there a chance the new one is bad too? Replaced with GM part The A/C was rebuilt about 4 years ago.

Thanks for your time!!
Kevin
Unhook battery for five minutes se if that helps
 
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