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Everything works, yet it doesn't pump

JeremyBMW on Wed August 04, 2010 8:35 PM User is offline

Year: 1993
Make: Winnebago
Model: Adventurer
Engine Size: 454
Refrigerant Type: R12

Replaced thus far: Receiver/drier (old one blew the desiccant pack), assorted o-rings, replaced original SD-709 with SD7h15 due to the fact that the place didn't have any 709s in stock. While apart, the condenser was flushed. The compressor was drained of its factory oil (it's designed for R134a), flushed with mineral oil, and refilled with mineral oil. Oil was added to the low side line and blown through with air to replace the oil that'd come out in the flush. All lines were confirmed free of obstruction with compressed air before reassembly.

Vacuum was pulled for an hour, held perfectly over 45 minutes with pump off. Jumping two pressure switches in the engine compartment (one near evaporator, one near receiver/drier), we get power to the compressor clutch. Connected the gauges to an R12 tank, opened low side, then high side, and allowed vacuum to pull in what refrigerant it could, then closed both sides. Then we started the motor and turned on the A/C and opened the low side valves.

Compressor makes a "not good sounding" clicking type of noise, builds no pressure on the high side and pulls no R12 in on the low side.

I'm out of ideas. Aside from a defective compressor, what could be wrong in this situation?

JeremyBMW on Fri August 06, 2010 4:58 PM User is offline

Bump for ideas.

iceman2555 on Fri August 06, 2010 5:39 PM User is offlineView users profile

The compressor was never designed to 'pull' refrigerant into the system. The system should be properly charged utilizing the correct recharge equipment.
Sandens compressor require specific lubrication procedures. Lube should be added to the case of the compressor thru the port in the compressor case, hopefully this was the procedure used!
The total system should have been flushed and cleaned. The post does not elude to this being done. It is possible that the system retains contaminates from ruptured desiccant. The txv could be contaminated with this same material.
All of these issues should be addressed. It is quite possible that the txv is not operating as it should and this is a major contributor to the lack of pressure build up. The 'defective' compressor issue could be the result of recontamination due to residual desiccant debris....possibly a damaged reed valve. This is a very good possibility considering the lack of through cleaning expressed in the post.
A suggestion would be back to square one. Flush and clean the system thoroughly utilizing as much flush chemical that is necessary. Inspect or replace the txv, add the proper amount of lubricant to the system. Insure that the compressor is properly lubricated. Replacement of the drier/filter would be a good idea also. Evac and recharge the system. Post results.

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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

bohica2xo on Fri August 06, 2010 8:03 PM User is offline

Ice, he refused to consider flushing the system HERE.

He discovered to the blown desiccant bag HERE

Jumping switches is just icing on the cake. The condensor was "flushed" according to this thread, but how or with what is unknown.
.
.

Jeremy:
A blown desiccant bag indicates either a lot of moisture, or the presence of 134a. It requires through cleaning & flushing of the entire system to prevent a second compressor failure. All of your previous labor was for nothing. You get to go back to square one. Hope the new compressor is ok.

B.

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"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.

JeremyBMW on Sat August 07, 2010 1:45 PM User is offline

Actually, much transpired between those posts and the current state of the system. As I stated above, the system was flushed from the low side line to the compressor to the receiver/drier connection. An Autozone "flush in a can" was used due to the inability to source anything else in time (those parts are now on order). Unfortunately, the txv connections are stuck fast, and the is mounted in a way where things are likely to break from excessive torque being applied to the connections. For such a huge vehicle, access to certain components is really less than optimal. That is why that side of the system was not flushed. No desiccant came out when flushing the condenser side, so the thinking was that it was unlikely that any made it to the high side. Compressor was lubricated properly per instructions, R134a has never been in this system.

That said, yes, I will be starting at square one when the vehicle returns. Would turning the compressor over by hand on the bench be enough to confirm whether it's good or bad? I did this originally when flushing the old oil out and installing the new oil. Assuming it still turns with the same resistance and makes pressure against a hand held over the high side port, is it most likely good?

As for jumping switches, I was lead to believe (elsewhere) that this was standard and ok for getting some charge into the system during charging. Should it not be necessary if everything is working as it should?

I realize that some stupidity was likely demonstrated in my earlier attempts. I was in a hurry, and that's no time to be learning something new. Any help or guidance is appreciated.

iceman2555 on Sat August 07, 2010 2:07 PM User is offlineView users profile

If necessary remove the evap cast/evaporator to access the TXV. It is high suspect if there are no operational pressures. This will also insure that the system can be completely cleaned. The evap is the source of most lubricant storage in a TXV system....clean it. Also, gives one a chance to inspect the evap for possible leakage.
If the connections are not and will not break loose...cut them with a dremel tool and replace the damaged parts. If the TXV must be cut....it is should be replaced from the beginning. Be care and do not damage the threads......it is a bit tedious...but can be done.
Once the parts are no longer confined to the vehicle...it is easier to 'break' them loose. Good luck.
This system must be cleaned...no 'if, and or buts' allowed. Take the time to do it right....the resultant benefit is well worth the effort.
The compressor maybe operational....the concern.....the noise issue in the previous post.....if in doubt.....obtain another...heck....you are going to turn in on warranty any way.....right?????
The AZ 'Flush in a Can' is as worthless as.....well....lets simply say it is worthless. Any flush in a can...other than the quarts and gallons that a closed loop machine utilizes is worthless. There is an insufficient amount of flush chemical to do much cleaning.

-------------------------
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

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