This is what the A-6 compressor drain plug is for!

[Domenic T.]

Get a few questions about how to know if you have to much or not enough oil in the A/C system.
The A-6 drain plug should be named the oil level plug. The manual trans and the differential have a upper plug that you can fill and check the oil level, usually 1/2" below when cold. The A-6 drain plug is above the bottom of the compressor oil pan. It is there to bleed out excess oil in the system. You could probably use it to see if there is not enough oil also. I would pass on that.
The A-6 drain plug has a hole drilled thru the center that joins 2 holes just under the head of the plug. It was designed to drain excess oil and only loose a fraction of the system pressure. It will make a mess when done correctly as any excess oil will squirt out first. The gas will hiss when the oil is correct. You only slightly loosen the plug to do this. This procedure is in the manual and tells you how long to run the system to drain the excess oil and to re drain if necessary.
Pumping oil will get things hot like a hydraulic pump. The auto trans cools it's oil going thru a tube in the hot radiator. To much oil can heat the system up and also the engine because the A/C condenser is in front of the radiator. The later A-6 compressors had a thermal switch on the back plate of the compressor. It got it's temp from the high side pressure inside the compressor and would send a signal to release the compressor clutch if the system was overheating.
The A-6 has a oil pump, oil pick up tube, and oil pan that should have over 4 oz of oil in it. The oil lubricates 2 case bearings, 2 thrust bearings, front seal, and piston rings.
Thought this might help now that things are warming up.

DOM

[Wayne M.]

Re: This is what the A-6 compressor drain plug is for!

Dom

Here's a Robinair A-6 dipstick that I got off eBay; no level markings on it.

Back in the '90s, when I had visions of doing work on my compressor(s), I acquired enough of the Robinair tools to at least R & R clutch, pulley, bearing, seal, etc.


A-6 dipstick.jpg

[Domenic T.]

Re: This is what the A-6 compressor drain plug is for!

Wayne,
I wonder if that is in the special tool section at the end of the chapter? That one would require complete loss of system pressure. Another thing that makes the oil level so variable is the mounting and belt adjustment. I can see where that would work well with the compressor in place changing a seal.
Some of the new ceramic seals do not have the lip on them that was used for extraction. In that case you must take the compressor apart.
For a seal replacement only I think it is much better to remove the compressor and replace all the seals. Usually a clutch/pulley out of balance or damage causes the leak from vibration. With half the seal on the shaft and the other half in the case, vibration between the 2 seal halves can start to leak.
So much more that can be checked that is usually the problem. Bent shaft, damage on the O-ring surface, pulley/clutch damage, and bearing failure. I'm sure you could add a few more ways for them to leak.
With a total tear down the shaft can be checked for drop damage, hammer damage, and thrust bearing damage caused by a drop or someone using a hammer to install the clutch hub. Unfortunately the clutch hub assembly at best was bad and is a source for vibration. With a metal to metal clutch, there are many ways to get out of center especially when engaged at high RPM.

DOM

[Jim T.]

Re: This is what the A-6 compressor drain plug is for!

Domenic have you ever changed the front seal leaving the compressor on a Corvette or other car?

[Domenic T.]

Re: This is what the A-6 compressor drain plug is for!

Jim,
No I never did one on the car, only pulley or clutch.

Dom

[Ken A.]

Re: This is what the A-6 compressor drain plug is for!

Actually, the front drain plug is also the fill plug for the system after it has been flushed and you're starting to pull vacuum.

[Richard M.]

Re: This is what the A-6 compressor drain plug is for!

I would never attempt to replace a seal with a A6 mounted on a car. It's tough enough on the bench.

P1010005.JPGP1010006.JPGP1010007.JPGP1010011.JPGP1010012.JPGP1010013.JPGP1010014.JPGP1010015.JPGP1010016.JPGP1010017.JPGP1010018.JPG

[Domenic T.]

Re: This is what the A-6 compressor drain plug is for!

Richard,
You are exactly on.

Dom

[Richard M.]

Re: This is what the A-6 compressor drain plug is for!

Yes, but I have to admit something......The one in my photos wasn't from a Corvette. This one was deep inside the Vee of a Jaguar V12. You can see the effects of the seal issue. However, the seal design "expects" a small amount of oil to be extracted from the unit to keep the ceramic seal lubricated. In the cavity of the A6 housing, a cylindrically shaped felt seal(pic above in the background with the clutch/pulley pic) keeps it in check. When the seal gets saturated, like the one above, too much oil escapes and makes a mess. Particularly not good for a fiberglass hood!

P9090005.jpg

Rich
p.s. Wife's car....I'm just her mechanic!

[Domenic T.]

Re: This is what the A-6 compressor drain plug is for!

Rich,
I read something to that effect as to expect some seepage, but I have a extra few things that I do that get them seep proof. None can be done unless compressor is apart.
I use a dremmel tool and buff the O ring surface in the front cover that cannot be done with shaft in place. Then polish the O- ring surface on the shaft. Both give a positive O-ring surface. The felt then catches the initial lube that was used to assemble the seal. The front bearing hole in the shaft takes care of the lube on the ceramic.
That's why I answered Jims question telling him that I never did one in place. Rich, also using over 300 PSI of nitrogen on the seal test seems to seat all the other O- rings. I buff those surfaces also. I think a reseal with the gut PAC out would only take a little more time.
I know you do all your own work and would like to share one more thing that I find. The balance of the pulley, sure it is not mounted to the shaft but when the hub clutch engages to the pulley it can shift a bit on the out of balance pulley and vibrate the shaft that holds half of the seal causing a leak. The front hubs are really out of whack but for some reason seem to work well. If you spin one on your lathe you will see how bad the hubs are. Some I just do not use. A metal to metal clutch!!

DOM

[Richard M.]

Re: This is what the A-6 compressor drain plug is for!

Good info Dom, thanks for sharing it.

Rich

[Christopher K.]

Re: This is what the A-6 compressor drain plug is for!

Dom
Have you tried the new double lip seal? Some have had good luck with these as long as the shaft is smooth with minimal runout.

[Domenic T.]

Re: This is what the A-6 compressor drain plug is for!

Chris,
I was sent some years ago and would not use them, not that double lip seals are not good, but the compressor shaft at that point is about 9/16". As you know the lip will now be stationary and the shaft will spin inside. The shaft is not that hard and I think this will eventually wear the shaft and the rubber somewhat like the front seal on the engine does to the harmonic balancer.
With that sized shaft using the ceramic seal, nothing is rubbing the shaft because 1/2 of the ceramic seal is attached to the shaft with 2 flats and sealed to the shaft with a O-ring. That rotates with the shaft. The other 1/2 of the ceramic seal is attached to the front case flange and also seals to the flange with a O-ring. It is stationary and does not spin. The only 2 parts that touch and can wear are ceramic. The 2 ceramic halves are pushed together with spring pressure to get the seal. In this case nothing wears but the ceramic.
I was basic on my answer to you so others could understand your question. I really think the double lip seal would have a much shorter life span and cause the shaft to get a groove that would weeken the already weak shaft.

Dom

[Christopher K.]

Re: This is what the A-6 compressor drain plug is for!

Dom
That's a great detailed explanation of how the ceramic seal works. I'm replacing mine next week and I have both kinds so I'll have to make a decision about which to use. The big rebuilders seem to be using the double lip now but I have not seen any long term test results nor any feedback from anyone. The extra steps you outlined on your rebuild no doubt make the difference on the longevity of the ceramic seal.
Thanks again,

[Richard M.]

Re: This is what the A-6 compressor drain plug is for!

Rich,
I read something to that effect as to expect some seepage, but I have a extra few things that I do that get them seep proof. None can be done unless compressor is apart.
I use a dremmel tool and buff the O ring surface in the front cover that cannot be done with shaft in place. Then polish the O- ring surface on the shaft. Both give a positive O-ring surface. The felt then catches the initial lube that was used to assemble the seal. The front bearing hole in the shaft takes care of the lube on the ceramic.
That's why I answered Jims question telling him that I never did one in place. Rich, also using over 300 PSI of nitrogen on the seal test seems to seat all the other O- rings. I buff those surfaces also. I think a reseal with the gut PAC out would only take a little more time.
I know you do all your own work and would like to share one more thing that I find. The balance of the pulley, sure it is not mounted to the shaft but when the hub clutch engages to the pulley it can shift a bit on the out of balance pulley and vibrate the shaft that holds half of the seal causing a leak. The front hubs are really out of whack but for some reason seem to work well. If you spin one on your lathe you will see how bad the hubs are. Some I just do not use. A metal to metal clutch!!

DOM

Hi Dom, Old A6 thread resurrected...

What would cause the A6 compressor to seize when I turned on the AC? R12 system serviced about 5 years ago. I thought it was running ok but saw smoke from the hub/clutch so I shut it off right away. Car sat inside but not run since June 2017 but AC cold then.

Should I try to wrench the hub to free it up or am I dreaming? I suppose the clutch is now junk too.

Thanks,
Rich