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Compressor Overheating

JimLavL on Wed July 28, 2010 1:23 PM User is offlineView users profile

Year: 2001
Make: Chevrolet
Model: Suburban
Engine Size: 8.1 L
Refrigerant Type: 134a
Country of Origin: United States

Last weekend (95+ degrees) I sprung a leak in the high pressure switch on the back of the 10S20F compressor in the Suburban. I replaced the switch and while my mechanic was recharging and running the system, the new switch MELTED in half. The connector end was dangling still connected to the wire and the other half was melted into the back of the compressor.

It does not look like it was an electrical issue - the exposed switch terminals and the connection end of the switch all looked perfect. The compressor and refrigerant hoses were very hot an hour later when he brought it back to me and told me the story.

Any experience with this compressor burning up from the inside? Would broken valves or some other condition cause this kind of heat buildup? (No loud noises were present.)

I am going to replace compressor/accumulator/O tube tonight and flush what lines I can. I read other posts in other places that say 6.5 ounces of oil - is that total? Should I try to see what comes out and subtract, or should I plan on putting this much in?

Thanks - Jim

JimLavL on Wed July 28, 2010 1:39 PM User is offlineView users profile

Correction - the compressor information talked about 6.5 oz. I found a pretty reliable "system" chart that indicates 11 oz of PAG 46.

How much do I add? Should I assume that the original 11 oz is in the system and only charge what I take out? What about the leak - did I lose oil during the previous system dump?

How do you tell? What goes wrong if you put too much in? (I know what happens if you don't have enough...)

bohica2xo on Wed July 28, 2010 1:58 PM User is offline

Was the original switch cracked, or was it just an O ring leak?

Where did you get the replacement switch?

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

JimLavL on Wed July 28, 2010 3:07 PM User is offlineView users profile

In retrospect, I believe the original switch was beginning to melt/deform. It was loose from the metal cup, slightly cocked to one side, and rocking around in the cup. It did not appear to be cracked or broken within the plastic itself, only loose from the metal. The leak was obviously coming through the part itself, not from the O ring. The O ring looked fine when I popped the old switch out. The new one came with a new O ring.

The new part (20055) was ordered into the local Advance Auto Parts. Nobody seems to have one on the shelf.

I just found out the rebuilt compressor I ordered does not have one of these in it, but the guy found one at a nearby supply house. I should have everything to do the job tonight.

iceman2555 on Wed July 28, 2010 5:42 PM User is offlineView users profile

Sure sounds like a electrical problem to me.....the amount of heat necessary to melt plastic that is about 1/2 from the compressor case would be difficult for a compressor to produce. This is an exorbitant amount of heat......think the compressor would have failed long before the plastic melted.
Could you please supply the part number of the switch that was used....the correct unit is very specific for this vehicle....and perhaps...the incorrect switch was used. GM does not service this switch....well....they do...but it comes wrapped in a new compressor. Post your info concerning this switch.
The compressor is mounted in a high heat area....near the exhaust manifold....but even this amount of heat sounds extremely high.
My first choice...check the electrical circuit.....and insure the switch is correct.

-------------------------
The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

JimLavL on Wed July 28, 2010 6:37 PM User is offlineView users profile

The switch is a Four Seasons 20055. That is listed by all the auto parts stores as the correct one for my vehicle, and it looks identical to the one taken off (purple 2 prong connector).

The original switch had a number 22800, which cross referenced to the F.S. 20055. (The OEM part costs 5 times more, but that's still less than a compressor, eh?).

I did not see anything about the exposed electrical components to indicate a short. It looks like the plastic melted at the interface with the metal cup - circlular break with stringy melted ends right at the crimp.

bohica2xo on Wed July 28, 2010 9:07 PM User is offline

I was leaning toward substandard plastic materials in the replacement switch, but you say the OEM switch had melted as well.

I am looking at the wiring diagram for a 2001 C2500 Suburban. I see two switches on the compressor.

One has a BLK wire & a DK GRN wire. This switch connects to ground & the PCM. At most, it carries 5v @ 100ma.
The second switch has a LT BLU wire, & a DK GRN/WHT wire. This connects to the PCM, and the HVAC module. Again, almost no power on this circuit.

The only way I see that this could be an electrical issue would be if the Dark Green wire had somehow become connected to a +12v source. This would create a dead short to ground through the switch.

I just don't see this as an electrical problem, that wire should be smoking if it generated enough heat to melt the switch.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

JimLavL on Thu July 29, 2010 12:09 PM User is offlineView users profile

Well, it definitely needed a new compressor. There were plenty of little black or shiny pieces floating around in all the oil I flushed out last night. When you turn the old compressor it whould stop on the way and take about "pickle jar opening" pressure to get it past the stop point. I imagine that it was chewing up the vanes in preparation for a big sieze.

I didn't realize how much you have to deconstruct the back of the interior to get to the rear evap. Luckily, I had my ex-auto body friend with me to help.

Orifice tube and TXV screen were caked with black and shiny particles. Everything that got flushed was dark green - kept at it until flush ran clear. New accumulator and orifice, some new O rings. My mechanic is going to evacuate, leak check, and charge tonight, so I still don't know if it's right.

By the way - my original question was about the oil. I put 4 oz in the accumulator before buttoning up. It seemed like the factory rebuilt compressor had oil in it. How much? All you parts sellers should have some idea.

Thanks

bohica2xo on Thu July 29, 2010 12:32 PM User is offline

Actually, that compressor has ten pistons, not vanes... and it was coming apart rather spectacularly apparently.

I see 3 different compressors for that truck. HT6, 10S17F, 10S20F With a new compressor up around 375 bucks, it is best to do this job once.

If you found chunks on the OT, that 6mm piccolo condensor has about a half pound of your old compressor still in it. I would replace it, rather than risk starting the cycle again in a few months.

Since you already opened the rear evaporator, you got the hard part done. Flush the lines, clean the TXV. Put a new condensor in it.

Then you can add back the total system oil quantity without issue.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

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