Author Topic: Compressor rebuilders  (Read 536 times)

Warren Seale

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Compressor rebuilders
« on: October 12, 2019, 09:49:52 AM »
My A6 compressor needs a rebuild after 40 years of service.  It rattles and has very hot high pressure lines but the low side is warm.  It also will not take any additional Freon 12.  I want to keep my original rather than swap it out for another.  I know the Original Air Group (Classic Auto Air) in Tampa is pretty well known for servicing old AC systems.  Does anyone else know of a reliable compressor rebuilder?
79 T/A,WS6,403,A3
96 T/A,WS6(#1344),M6
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cyber104

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Re: Compressor rebuilders
« Reply #1 on: October 13, 2019, 05:42:18 AM »
A few questions............

1)  Is the system currently charged?

2)  What are the high/low side pressure readings when the car and compressor are running

3)  You say it won't take any more R12 - what do you mean by that?

4)  If the system is not charged - have you tried pulling a vacuum?

Without a proper gauge set you are at a real disadvantage - do you have a set?  A6 compressors are TOUGH - are you SURE it's a compressor problem and not a leak or undercharge/overcharge situation.

Chris
1978 TA 4-Speed W72

Warren Seale

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Re: Compressor rebuilders
« Reply #2 on: October 13, 2019, 08:39:34 AM »
A few questions............

1)  Is the system currently charged?

2)  What are the high/low side pressure readings when the car and compressor are running

3)  You say it won't take any more R12 - what do you mean by that?

4)  If the system is not charged - have you tried pulling a vacuum?


Without a proper gauge set you are at a real disadvantage - do you have a set?  A6 compressors are TOUGH - are you SURE it's a compressor problem and not a leak or undercharge/overcharge situation.

Chris

Yes the system is charged.

I have gauges but have not checked the pressures yet.  I know the high side is pretty warm, I would say near 50 deg C. just before the orifice tube.  From memory I estimate that it is hotter than normal.  You can't hold your hand on it too long without discomfort.  Right after the orifice tube, at the input to the evaporator, the pipe is cold but the output side of the evaporator is at ambient air temp.  The compressor does not cycle on/off due to low pressure.  When the compressor is turned on it has the normal load on the engine.  In other words the RPM drops slightly.

I've tried to charge it but it does not readily draw the Freon in.  The last time I tried to charge it some Freon went in but it took a long time to get it in there and it did not improve the performance by much.  Normally, with a low charge, the stuff goes in pretty fast and the performance improves quickly.

It seems to me that the orifice tube filter is clogged possibly from debris coming from the compressor. 

This problem has been slowly getting worse over time.  It didn't suddenly happen.

I don't like the way the compressor sounds.  It is louder than normal.

« Last Edit: October 13, 2019, 08:41:58 AM by Warren Seale »
79 T/A,WS6,403,A3
96 T/A,WS6(#1344),M6
72 442,W30,A3
96 Vette Grand Sport convertible,F45,LT4,M6
06 Vette convertible,Z51,M6

cyber104

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Re: Compressor rebuilders
« Reply #3 on: October 13, 2019, 10:57:38 AM »
You really need to check the pressures - both high and low side with the car running and the compressor running.

What is the temp of the air coming out the vents?

You will not be able to get additional R12 into the system in hot weather - or - if the system is cycling and the engine is hot.

I respect what you are saying about the compressor getting louder - but without pressure readings I really can't offer good advice

Did you see the pressure vs. temperature chart I posted a while back?
1978 TA 4-Speed W72

FormTA

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Re: Compressor rebuilders
« Reply #4 on: October 13, 2019, 12:18:39 PM »

Warren Seale

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Re: Compressor rebuilders
« Reply #5 on: October 13, 2019, 03:35:53 PM »
You really need to check the pressures - both high and low side with the car running and the compressor running.

What is the temp of the air coming out the vents?

You will not be able to get additional R12 into the system in hot weather - or - if the system is cycling and the engine is hot.

I respect what you are saying about the compressor getting louder - but without pressure readings I really can't offer good advice

Did you see the pressure vs. temperature chart I posted a while back?

The temperature out of the vents is marginally cooler than ambient.  It's not really enough to be useful. 
I have a temp vs pressure chart.

I'll check the pressures in the next day or two.  I think what I might do first is to replace the orifice tube (it's the original) and recharge it.  If the screen is clogged then, thinking positively, it might be the result of 40 years worth of normal wear and tear and be hopeful that the compressor is fine.

79 T/A,WS6,403,A3
96 T/A,WS6(#1344),M6
72 442,W30,A3
96 Vette Grand Sport convertible,F45,LT4,M6
06 Vette convertible,Z51,M6

Aus78Formula

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Re: Compressor rebuilders
« Reply #6 on: October 13, 2019, 10:41:16 PM »
If the compressor is overheating, it's likely that the lines are restricted or blocked, as suspected, and therefore not operating efficiently. It could be years of gunk building up around the orifice tube, but could also be the particles of a worn compressor.

Warren Seale

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79 T/A,WS6,403,A3
96 T/A,WS6(#1344),M6
72 442,W30,A3
96 Vette Grand Sport convertible,F45,LT4,M6
06 Vette convertible,Z51,M6

FormTA

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Re: Compressor rebuilders
« Reply #8 on: October 14, 2019, 11:11:15 AM »
I have not. I found it when I was searching for a refrigerant for a refrigerator. Those guys seem to swear by it.
79 Trans am 301 (work in progress) LS swap n progress
79 Formula 301 (Work in progress)
67 RS Camaro (Work in progress)
See the recurring theme???

Names, Luke. If I hear anyone telling me they're my father....

Warren Seale

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Re: Compressor rebuilders
« Reply #9 on: October 15, 2019, 10:20:11 AM »
You really need to check the pressures - both high and low side with the car running and the compressor running.

What is the temp of the air coming out the vents?

You will not be able to get additional R12 into the system in hot weather - or - if the system is cycling and the engine is hot.

I respect what you are saying about the compressor getting louder - but without pressure readings I really can't offer good advice

Did you see the pressure vs. temperature chart I posted a while back?

Chris,  I got my gauge set on there and have 38 psi on the low side.  Unfortunately my gauge set does not have the smaller high side Schrader valve fitting so I took a couple of temperature measurements with a thermocouple.  The pipe just before it enters the compressor is 98 deg C.  Scary hot!  The pipe just before the orifice tube is 56 deg C.  Just for the heck of it I tried to add some R12.  It took about a 4 oz and did not make a difference, clearly not normal.  The pipe right after the orifice tube and before the evaporator was frosting up but the pipe out of the evaporator is at ambient temp. 

The test conditions are ambient temp about 80 deg F, control set on Normal and the fan on high.  Windows open.
« Last Edit: October 15, 2019, 10:36:00 AM by Warren Seale »
79 T/A,WS6,403,A3
96 T/A,WS6(#1344),M6
72 442,W30,A3
96 Vette Grand Sport convertible,F45,LT4,M6
06 Vette convertible,Z51,M6

cyber104

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Re: Compressor rebuilders
« Reply #10 on: October 15, 2019, 11:53:32 AM »
The low pressure side is good.  We REALLY need that high pressure side reading.  At 80 deg F I'm expecting about 180 PSI for R12.

If the pipe right after the orifice tube is frosting up that's good!

The fact that the pipe returning from the evaporator is ambient is a bit strange - it suggests a blockage after the orifice tube - or - your heater is operating simultaneously, introducing hot air into the cold air.  Are you certain your heater door is closing?

Can you get a high-side reading?

Is the compressor cycling on and off? (it should be)

Chris
« Last Edit: October 15, 2019, 11:56:11 AM by cyber104 »
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Warren Seale

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Re: Compressor rebuilders
« Reply #11 on: October 15, 2019, 12:36:38 PM »
The low pressure side is good.  We REALLY need that high pressure side reading.  At 80 deg F I'm expecting about 180 PSI for R12.

If the pipe right after the orifice tube is frosting up that's good!

The fact that the pipe returning from the evaporator is ambient is a bit strange - it suggests a blockage after the orifice tube - or - your heater is operating simultaneously, introducing hot air into the cold air.  Are you certain your heater door is closing?

Can you get a high-side reading?

Is the compressor cycling on and off? (it should be)

Chris

I can't readily get a high side pressure unless there is an adaptor available or a hose that has the smaller fitting.  Can't we simply convert the pipe temperature to pressure?  The 98 deg C is right at the high pressure fitting. 

The temperature door bangs when the lever is moved. 

The compressor does not cycle which is what I expect since the low side pressure is not that low.  The compressor typically shuts off when the pressure gets below ~20psi.

I'm pretty sure a clogged orifice tube is causing a blockage.  I just hope that it is not clogged due to a compressor problem.

Is it possible that the compressor is loud due to the very high head temperature (pressure)?




79 T/A,WS6,403,A3
96 T/A,WS6(#1344),M6
72 442,W30,A3
96 Vette Grand Sport convertible,F45,LT4,M6
06 Vette convertible,Z51,M6

cyber104

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Re: Compressor rebuilders
« Reply #12 on: October 16, 2019, 05:42:55 AM »
Actually - the compressor should cycle - it should not remain on constantly..........

High head pressure could be the problem - I guess replace the orifice tube and lets see what happens - have fun removing it - I had to use a heat gun
1978 TA 4-Speed W72

Warren Seale

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Re: Compressor rebuilders
« Reply #13 on: October 16, 2019, 10:07:04 AM »
I'm finding that, in my area, there are no shops willing to evacuate (give credit for the captured Freon) and charge an R12 system.  They say they don't have "the machine" and are not able to source the R12.  So I'm entirely on my own here and will have to vent it to the air.
79 T/A,WS6,403,A3
96 T/A,WS6(#1344),M6
72 442,W30,A3
96 Vette Grand Sport convertible,F45,LT4,M6
06 Vette convertible,Z51,M6

cyber104

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Re: Compressor rebuilders
« Reply #14 on: October 16, 2019, 12:03:37 PM »
Where are you located Warren?
1978 TA 4-Speed W72

Re: Compressor rebuilders
« Reply #14 on: October 16, 2019, 12:03:37 PM »



Warren Seale

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Re: Compressor rebuilders
« Reply #15 on: October 17, 2019, 10:24:47 AM »
Where are you located Warren?

Melbourne FL.
79 T/A,WS6,403,A3
96 T/A,WS6(#1344),M6
72 442,W30,A3
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06 Vette convertible,Z51,M6

cyber104

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Re: Compressor rebuilders
« Reply #16 on: October 18, 2019, 06:19:21 AM »
Warren - this statement has me wondering..................

"Can't we simply convert the pipe temperature to pressure? "

Just because the pipe is hot doesn't mean we can calculate the inside pressure - at least from a physics perspective I'm not sure how you could do that?
1978 TA 4-Speed W72

Warren Seale

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Re: Compressor rebuilders
« Reply #17 on: October 18, 2019, 12:25:42 PM »
Warren - this statement has me wondering..................

"Can't we simply convert the pipe temperature to pressure? "

Just because the pipe is hot doesn't mean we can calculate the inside pressure - at least from a physics perspective I'm not sure how you could do that?

The pressure will be proportional to temperature.  The fact that the hot line is 98 deg C indicates an unusually high pressure.  Nevertheless, I think there is a clog and it is most likely in the orifice tube screen.  I just received my supply of R12 so I'll have a go at it early next week.
79 T/A,WS6,403,A3
96 T/A,WS6(#1344),M6
72 442,W30,A3
96 Vette Grand Sport convertible,F45,LT4,M6
06 Vette convertible,Z51,M6

Warren Seale

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Re: Compressor rebuilders
« Reply #18 on: October 18, 2019, 05:44:29 PM »
Actually - the compressor should cycle - it should not remain on constantly..........

High head pressure could be the problem - I guess replace the orifice tube and lets see what happens - have fun removing it - I had to use a heat gun

Chris,  Did you use an orifice tube removal tool?  If yes is it like this one?

https://www.jbtools.com/mastercool-91002-gm-and-ford-a-c-orifice-tube-remover-and-installer/?gclid=CjwKCAjwxaXtBRBbEiwAPqPxcOpmmHdEUWHe06Xk5Gf99IIb_ZCdttyuuLCd18brXM6ma043b_Rx4xoCEq8QAvD_BwE

Here it is in action.

https://www.youtube.com/watch?v=vLAvCNts1JY

« Last Edit: October 18, 2019, 05:48:59 PM by Warren Seale »
79 T/A,WS6,403,A3
96 T/A,WS6(#1344),M6
72 442,W30,A3
96 Vette Grand Sport convertible,F45,LT4,M6
06 Vette convertible,Z51,M6

cyber104

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Re: Compressor rebuilders
« Reply #19 on: October 19, 2019, 06:37:29 AM »
Warren - this statement has me wondering..................

"Can't we simply convert the pipe temperature to pressure? "

Just because the pipe is hot doesn't mean we can calculate the inside pressure - at least from a physics perspective I'm not sure how you could do that?

The pressure will be proportional to temperature.  The fact that the hot line is 98 deg C indicates an unusually high pressure.  Nevertheless, I think there is a clog and it is most likely in the orifice tube screen.  I just received my supply of R12 so I'll have a go at it early next week.

Are you sure?  That pressure/temperature chart is referring to outside air temperature - not the temperature of the pipe.

Either way it doesn't matter I guess.

I've seen those tools and they work well.  I didn't have one so I just used pliers.  I had to heat the metal line up with a heat gun - the o-rings on the orifice tube often get stuck to the inner wall of the tube - heat breaks the bond.
1978 TA 4-Speed W72

olds403

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Re: Compressor rebuilders
« Reply #20 on: October 19, 2019, 08:03:57 AM »
 That Maxi frig is flammable and its largely propane based.  Why not get the R12 in your system recovered into a recovery machine ?  Guess its a dying bred of old guys left. Same like trying to get our TATA painted....everyone just wants a quick in and out or the other side - paint jail


Speaking from experience......

You will need to completely purge the system and flush it and replace the oil in the compressor.  Read what you want on the internet- we always purge and flush.  Its probably loud due to clutch, clutch beariing or the axial / guts of the compressor is done.  I have quite a bit A6 spare parts....let me look later today. 

I know original matters - though the sanden FLX7 mod that i posted is amazing when paired on older cars.  Its easy and when doing a new system that needs replacing.  Parallel flow condenser and r134a orfice  Tube.  This is exactly what we are doing and why we sold our NOS A6 compressors.  No more hassle and modern compressor with 7 cylinders.  Plus all R134A and works. 

Fyi My brother is EPA certified for freons and we both used to do automotive A/C and had certs

Not saying this is what you want to do but here are the details.    I can crimp lines

http://transamcountry.com/community/index.php?topic=79822.0

« Last Edit: October 19, 2019, 08:18:58 AM by olds403 »

firebirdparts

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Re: Compressor rebuilders
« Reply #21 on: October 21, 2019, 01:10:30 PM »
Pressure can be inferred from temperature only when you are experiencing phase equilbrium.  That is, you have liquid and vapor both present.  It's also important to be sure you know what the liquid and vapor are.  If there is any air in there, it will throw that off.  That temperature also has to be measureable.

That does not really work well on the condenser side.  The condenser is too hot at the inlet and too cold at the outlet to tell you pressure (exactly).  If you could measure temperature all over the condenser, then yes, you could do it. 

If the liquid side is restricted, it'll get real cold after the restriction and you can find problems that way.

Year ago I lost my late-70's-R12 high pressure adapter, and of course finding one of those today, good luck.  I managed to find one somewhere, I forget where.
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Warren Seale

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Re: Compressor rebuilders
« Reply #22 on: October 24, 2019, 09:01:53 AM »
Today I pulled the orifice tube and found that it was really very clear.  There were only a couple of metal fragments and a few strands of fibrous material after being in there for 40 years.  It was like 95% clear.  I replaced it with a new one and blew through the system from the input of the evaporator and found that there were no restrictions.  The air came out of the pipe that was disconnected from the evaporator pipe.  I thought that this would not work since the compressor is still in the path but surprisingly it did pass air.   So now I'm drawing a vacuum and testing for a leak where I opened it.

The bad news is I don't see any smoking gun.  I hate to throw $100+ of R12 into it only to find out the situation is the same.

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96 T/A,WS6(#1344),M6
72 442,W30,A3
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cyber104

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Re: Compressor rebuilders
« Reply #23 on: October 25, 2019, 05:24:44 AM »
Too bad about the tube - mine was near perfect also when I took it out 6 months ago and it was the original.

Keep at it - you'll figure it out.

At this point I'd really put some effort into finding an adapter that would let you get a gauge on both the high and low side.

Chris
1978 TA 4-Speed W72

FormTA

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Re: Compressor rebuilders
« Reply #24 on: October 25, 2019, 08:24:34 AM »
Bummer, I would have bet money that thing would have been plugged. For $60 I would try the MAXI Fridge.
79 Trans am 301 (work in progress) LS swap n progress
79 Formula 301 (Work in progress)
67 RS Camaro (Work in progress)
See the recurring theme???

Names, Luke. If I hear anyone telling me they're my father....

Warren Seale

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Re: Compressor rebuilders
« Reply #25 on: October 25, 2019, 08:46:34 AM »
I've been talking to Classic Auto Air and they gave me the run down as to what to do next.  Basically it amounts to removing the compressor, draining the oil from the sump, inspect it for debris, and checking the screen on the suction port.  Then attach a drill to it, spin it and check to see if it has and holds suction on the intake port.  Then remove the accumulator. flush the lines. and inspect for debris.  Reattach the accumulator, add 10 oz of Ester oil to the compressor (assuming it checks out OK) and reinstall it.  Fill the system with the cheaper R134a just to test it out.  Then I will purge the R134a, remove the accumulator and, if necessary, the compressor and send them off to get rebuilt.  The accumulator will most definitely need to be rebuilt since it has not been touched in 40 years.

The unknown right now is the condition of the compressor.  Hopefully this diagnostic procedure will shed some light.
79 T/A,WS6,403,A3
96 T/A,WS6(#1344),M6
72 442,W30,A3
96 Vette Grand Sport convertible,F45,LT4,M6
06 Vette convertible,Z51,M6

Warren Seale

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Re: Compressor rebuilders
« Reply #26 on: November 12, 2019, 03:22:30 PM »
I'm back on this again.  I removed the compressor and found the input screen was clean but then when I went to empty the oil sump, nothing came out.  Now I know there was oil in there when the seals were changed 16 years ago.  But as is typical a small amount of oil can be seen slung from the front seal during operation.
 
I did a bench test with the drill and found that there was suction on the input port and air being pumped from the output side.
 
What symptoms would you expect to see when there is low oil?  It was becoming noisy when it stopped cooling.
 
What do you all suggest now?  Should I flush the lines, add 10 oz of ester oil to the compressor, charge it with R134 and see what it does?
79 T/A,WS6,403,A3
96 T/A,WS6(#1344),M6
72 442,W30,A3
96 Vette Grand Sport convertible,F45,LT4,M6
06 Vette convertible,Z51,M6

cyber104

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Re: Compressor rebuilders
« Reply #27 on: November 13, 2019, 07:21:44 AM »
"What do you all suggest now?  Should I flush the lines, add 10 oz of ester oil to the compressor, charge it with R134 and see what it does?"

There is probably some oil left in the system somewhere so don't add 10 oz.  I'd add 8.5 oz.  In fact the compressor might not even take that much - sometimes it starts belching out of the rear ports before you get in what you "think" it should hold.

In addition to draining from the plug, I'd first stand the compressor on it's end and hand rotate it to pump out all the old oil the ports.

Yes - I'd charge it up and see how it goes.  Make sure you pull a vacuum and that it holds that vacuum for a LONG time.  Most guys go with 30 minutes to 1 hr.  I let mine sit overnight.

Good luck!
Chris

1978 TA 4-Speed W72

Warren Seale

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Re: Compressor rebuilders
« Reply #28 on: November 14, 2019, 10:05:52 AM »
After carefully listening to the compressor when turning it slowly by hand, I noticed that there was a grinding sound in one part of the compression cycle.  There was also a rough feel when it went through this part of the cycle.  This did not seem normal to me so I am foregoing the R134 test and sending the compressor and accumulator over to Classic Auto Air to be rebuilt. 
79 T/A,WS6,403,A3
96 T/A,WS6(#1344),M6
72 442,W30,A3
96 Vette Grand Sport convertible,F45,LT4,M6
06 Vette convertible,Z51,M6

Re: Compressor rebuilders
« Reply #28 on: November 14, 2019, 10:05:52 AM »
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