1st Generation Dodge Cummins 89-93 Discussion of 12 Valve 5.9 Liter Dodge Cummins Diesels with Rotary Injection Pumps

A/C Compressor not pumping?

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  #1  
Old 07-22-2011, 05:32 PM
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Default A/C Compressor not pumping?

I decided to go ahead and replace my compressor with a rebuilt A/C compressor because the coil went out on the old one. It seems like the compressor is not pumping. The low side readings are maxed out and if I rev the engine to 2500 rpm, it'll bring the low side down to maybe 30 on the R134a scale (about 3/4 the way up the scale). It also won't take any more refrigerant yet I've only put in less than half of what I need. What's going on? Could it be that it's too hot outside? Or does it sound like a defective compressor.

Also, the compressor turns over just fine.

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Also, the low pressure line is not getting cold. And yes, I did pull a vacuum before recharging.
 

Last edited by Edahall; 07-22-2011 at 05:36 PM. Reason: Automerged Doublepost
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Old 07-22-2011, 06:45 PM
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It's not the heat causing the problem... If you want to check the compressor to make sure it's doing what it should,drop all the refrigerant from the system,start the engine and set a/c to cool,jumper the low pressure switch and watch your lowside gauge,it should go from zero to 10 to 15 inches of vacuum in under 30 seconds,if it won't pull at least 5 inches,it's a dud!
 
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Old 07-22-2011, 08:45 PM
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Only1* is right on! good luck.
 
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  #4  
Old 07-23-2011, 05:49 PM
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Thanks, I will try that and report back.

---AutoMerged DoublePost---

Originally Posted by Only1*
It's not the heat causing the problem... If you want to check the compressor to make sure it's doing what it should,drop all the refrigerant from the system,start the engine and set a/c to cool,jumper the low pressure switch and watch your lowside gauge,it should go from zero to 10 to 15 inches of vacuum in under 30 seconds,if it won't pull at least 5 inches,it's a dud!
I followed your procedure and with the pump rotating, I didn't even notice a blip on the lowside gauge. It just stayed at 0.

---AutoMerged DoublePost---

Update: It's all working again. The verdict is the rebuilt pump was a dud. I ended up taking the coil and hub assembly off the rebuilt unit and put it on the old compressor. It blows very cold air now. The only problem left is the belt squeals real bad on the new hub assembly. If I spray some WD-40 on the hub, the squeal goes away. Is there any fix for this?
 

Last edited by Edahall; 07-23-2011 at 05:49 PM. Reason: Automerged Doublepost
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Old 07-24-2011, 10:14 AM
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If it's not a new belt,it could be glazed causing it to squeal,or possibly the belt isn't tensioned well and it's slipping.
 
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Old 07-25-2011, 08:13 AM
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The squeal was almost as loud as a skill saw. However, I knew it was just the belt so I went ahead yesterday and drove 500 miles and by the time I got back, the squeal was gone.
 
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