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Need help with A-6 compressor

botietruck on Sun August 10, 2008 1:01 PM User is offline

Year: 1971
Make: Chevrolet
Model: C-10 pickup
Engine Size: 250
Refrigerant Type: R134a
Ambient Temp: 80-90
Country of Origin: United States

I'm finishing a frame off restoration on my '71 Chevy p/u. All components of the system are new with the exception of the compressor which is a reconditioned NAPA unit and the factory expansion valve which is reconditioned. New NOS POA valve, new hoses, new condenser, Evap. core - everything new. I purchased the reman compressor about 6 -8 years ago and had it stored away until now. BTW, it does have a sticker indicating that it is compatible with R134a. Before installing the compressor, I drained the oil that it was shipped with and installed 11 oz.(per my GM manual) of Ester oil, putting all 11 oz. in the compressor. Pulled a vacuum yesterday and it held for a good 45 min. with no leakdown. After about 30 oz. of 134a, the compressor started acting like it was locking up. I shut it off and had some other things to do, so I have not gotten back on it. My questions are:

- Should I have not put all 11 oz. in the compressor? If no, did I damage the unit?
- The 2nd can of 134a (11 oz.) I put in upside down. I read that on an instruction sheet after the 1st. can was put in right side up. It stated that the first 2 cans should be put in upside down. Is this correct?
- At this point should I drain oil out of the compressor and add oil to the condenser or dryer?

Any ideas/thoughts are appreciated.


Dougflas on Sun August 10, 2008 1:07 PM User is offline

Ater you added the oil into the compressor, did you turn the hub about 10 times? Also I would have put the first can into the high side as liquid and then the rest as vapor into the lowside.

botietruck on Sun August 10, 2008 3:27 PM User is offline

I did rotate it several times after I put the oil in. Here's the latest update. Today I pulled the compressor back off & drained the oil into a new container. I measured out about 7 oz. and I figure I lost about an oz. or so on the floor. I removed the rear cover & inside plate from the compressor and carefully inspected the piston barrels & screen and looked for contamination. Other than the oil I drained out being a little dark, in my opinion, everything inside looked very clean. I reinstalled the rear cover & torqued nuts to specs. I plan to go back with 7 oz. of new ester oil and install the unit unless someone can point me in another direction.
So, I should put the 1st can of 134a in as liquid on the high side, and then the other cans as gas-right side up? Correct?

Chick on Sun August 10, 2008 4:36 PM User is offlineView users profile

Can you post the pressures, high and low, when it began to lock up?? The A6 has a sump, and you added the oil correectly..

Email: Chick


Freedoms just another word for nothing left to lose

iceman2555 on Sun August 10, 2008 6:05 PM User is offlineView users profile

If as the post states....the refrigerant was added as a 'liquid' during compressor operation, it is quite possible that the compressor 'locked' because of this method of recharge. One of the great things about the is easier to charge by cans (cylinders) without use of charging machine. The sump lubricant system keeps the compressor lubed during this process. It is not necessary to charge this system the method posted. Simply evac the system, add first can as a liquid or vapor...engage the compressor and then add the remainder as a vapor until the system is fully charged.

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.
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botietruck on Sun August 17, 2008 7:11 PM User is offline

Okay, here's the latest. I removed the old 4-blade engine fan and installed a new fan clutch with a 7-blade fan from my 350 V-8 engine, along with the correct fan shroud.
Yesterday, with outside temp. at about 85 degrees, I pulled a good vacuum at about 29 in. It held for a good 20 min. The engine was at normal operating temp. I then added about 50oz. of R134a and the low side pressure was running at about 30-40, it quickly shot up and pegged the gauge! The high side was up to about 150-175. I shut the engine off and the compressor would not rotate by hand. Again, as last weekend, I had other engagements and could not stay with it. This morning I checked the compressor and it rotates fine. Should I hook those gauges up again and see what it does, or possibly add another can of R134a? What would possibly cause the low side to spike like that.
BTW, just before it spiked, the left dash vent was blowing 60 degrees.

botietruck on Sat August 23, 2008 4:13 PM User is offline

This truck is driving me crazy!! I need some professional a/c advice. After reading the threads on resetting the POA valve, I pulled mine off and rigged up the fittings and set the valve at 26 psi. I checked it several times and it held there each time. I installed the valve this morning, along with a new dryer(added 1oz. of oil to the dryer), and pulled a good vacuum on the system for about 1 hour. I let it set for about 20 minutes with no loss of vacuum. I added about 50 oz. of 134a (the system holds 3.25 lb. of R-12.)
I cannot get the dash temp to go below 55-58 degrees.
I read somewhere on this forum that you could unplug the blower fan and watch the low side gauge and that will tell you where the POA is set. Well, I did that and it stayed right on 26-27. I watched the downstream side of the POA with the fan unplugged, and after a while it did start to freeze up. So, if I understand it correctly, the POA should be working okay.
I used a large carpenters clamp and blocked off both heater hoses, BTW, the heater hose shutoff is new, but I wanted to remove all doubt on that item.
I am open to ideas/suggestions. As stated earlier, everything in this system is new except for the compressor, and it is a NAPA reman, and the expansion valve has been rebuilt.
Here's the stats on 2 different times today.

-Ambient temp. 85 degrees
- engine rpm 1300
- High side - 245
- Low side - 47
- dash vent -58 with blower on high, with doors/windows closed.

Later today-ambient temp 93 degrees
- engine rpm 1300
- High side - 235-240
- Low side 50-53
- dash vent 58 with blower on high, doors/windows closed.
Now, here's a couple things I noticed
- There seems to be alot of condensation dripping out the bottom of the evap. box.
- The POA valve is sweating at both upstream & downstream end. That might be normal, just thought I would mention it.
- The expansion valve is sweating at the lower fitting also.
- The sight glass in the dryer is white, not cloudy, but white, looks like milk.

mk378 on Sat August 23, 2008 5:07 PM User is offline

Did you go from a tube/fin condenser to parallel flow? The system with new condenser may require less charge than the old spec. The passages inside a PF condenser are real tiny compared to those old 3/8" tubes.

Also be sure that your TXV sensor valve is properly attached to the line and well-insulated.

botietruck on Sat August 23, 2008 5:26 PM User is offline

I ordered the exact replacement condenser , it is an Old Air Products condenser. I'm pretty sure it is has the old style tubes. It looks just like the old one I took off.
When I installed the bulb for the TXV, I used the original clamps and it is insulated very well. I wasn't sure about the location of the bulb, so I have it positioned with the end of it just inside the evap case. Is that correct, or should it be on the outside of the case?

Edited: Sat August 23, 2008 at 5:27 PM by botietruck

botietruck on Sun August 24, 2008 4:29 PM User is offline

Okay, here's what I did today. Started the engine and switched on the a/c to high. Almost immediately I noticed the tube coming from the bottom of the evap core to the exp. valve started frosting over. It stayed that way for a while and then it started defrosting. I recorded the pressures from initial start-up until the fan belt gave way. (there is a long span between the compressor and the bottom pulley and the belt was not tight enough.)

Ambient temp. 82 deg.
cab vent temp 58 deg.

Low side (at start up 20 high side 175

3 min. later
low side 26 high side 205

3 min later
low side 31 high side 210

3 min later @ 90 deg
low side 34 high side 220

3 min later
low side 38 high side 230 cab vent @ 55

I started performing the test on the exp. valve using the ice water/hot water test and the belt broke.

3 min later
belt broke

Could the evap. tube frosting over so quickly indicate a faulty exp. valve/ Any comments on the they look okay?

Yogi on Mon August 25, 2008 1:32 PM User is offline

How do you have the controls set? Fan should be on high, Selector on "MAX" or "Recirc" and all doors and windows closed.

botietruck on Mon August 25, 2008 5:53 PM User is offline

The fan is on high, controls set to max a/c, doors & windows closed.

Edited: Mon August 25, 2008 at 5:54 PM by botietruck

powerflite on Tue August 26, 2008 1:54 PM User is offline

Sounds to me like you don't have enough condenser capacity. Check the fan clutch. If that is OK, see what happens if you spray the condenser with water at about 2000 rpm. If pressures drop and it gets appreciably colder, you need to either get a larger condenser or increase the air flow.

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