Pro6TEN compressor install on 1974 CdV with 472

[Chad Speer]

My A6 compressor failed catastrophically a few weeks ago.  The shaft sheared in the middle of the compressor, sending the clutch forward into the fan.  It appears that the damage is limited to the compressor and a dinged fan blade or two, so I'm probably lucky it wasn't worse.  I read somewhere (I think on this forum) that this was a "rumored" failure mode.  Well, I can confirm!  I had been trying to diagnose a periodic rumble that I felt, as much as heard.  I had definitely narrowed it down to being present only when the compressor was running, but the air was cold and it didn't seem too violent.  I probably should have been more concerned.  I suspect that it was a sign that I was low on oil, as I have to add R-134a at the start of each summer, but have not added oil.  Anyway, I could use some advice as I try to get her going again. 

The previous owner converted to R-134A and installed an Old Air Products VIR Eliminator kit.  He also bypassed the superheat switch, which appears to be a common move when installing the Old Air kit.  After the failure I ordered the Pro6TEN compressor from Old Air Products, which claims to be a drop-in replacement for the A-6.  After receiving it, I saw a couple of problems.  One, the distance between the front mounting plate and the rear mounting holes is slightly different than the A-6.  I can elongate a couple of holes in the rear mounting bracket to accommodate that.  The bigger problem is that Cadillac apparently used a different pulley offset than every other brand, because my A-6 single pulley sits about 3/8" forward of the Pro6TEN pulley.  Not quite the drop-in I was expecting, but I don't blame Old Air Products for that.  They reached out to the manufacturer for a solution, but said they don't expect a speedy response.

I could try to fabricate new mounting brackets for the Pro6TEN, but that's really beyond my current skills.  My thinking is to have the pulley modified, or have a new one machined to create the proper spacing. Before I get quotes for this from a machine shop, I was hoping to get some input from you guys.  Am I missing something simpler?




 

[TJ Hopland]

Are you sure the pulley on the old one hasn't walked forward a bit?   If not then do they offer a dual groove version?  Maybe the dual groove would give you more options for spacing?

The stock front bracket bolts to the block with vertical bolts doesn't it so not much you can do there?

Is that failure perhaps one of the things that happens from the clutch cycling maybe especially when the charge is low its short cycling and kicking on with higher load due to higher pressures from just recently have run? 

[Chad Speer]

Are you sure the pulley on the old one hasn't walked forward a bit?  If not then do they offer a dual groove version?  Maybe the dual groove would give you more options for spacing?

The stock front bracket bolts to the block with vertical bolts doesn't it so not much you can do there?

Is that failure perhaps one of the things that happens from the clutch cycling maybe especially when the charge is low its short cycling and kicking on with higher load due to higher pressures from just recently have run? 

I suspect that you described the failure mode about right, which means a rebuilt A-6 probably didn't make sense.  I decided to change compressor design rather than revert to the original VIR configuration, which I have no experience with.  I did just look at the pulley on the A-6, and I don't think it could have moved outward.  I mispoke when I said the pulley impacted the fan; it was the clutch.  I'll try to go back and edit that.  The A-6 pulley seems secure, and restrained by a snap ring.  I was nervous about removing the pulley on the Pro6TEN because it looked so strange, but those 6 "Frankenstein" bolts around the perimeter come out and there is no spring tension or anything to cause problems.  It just slips off.

The guy at Old Air Products mentioned the 2-groove pulley, but I don't even know if they make that anymore.  I can't find an example for sale online.  I don't know if either groove would align, but it might be easier to remove material from the 2-groove pulley than to add material to (or redesign) the 1-groove pulley.  If anyone has a source for the 2-groove pulley, I'd be interested.

I think you could remake both brackets to accommodate the differences, but it would be a project.  Notice that I didn't say that *I* could remake them!  Thanks for the ideas, TJ.  I just installed a shorter belt for the power steering and took her for a spin.  At least I'm back on the road for now.

[V63]

I believe the new aluminum A6 compressor you have is actually a drop in for GM EXCEPT Cadillac.

I bought one of those and I had to move the compressor forward 1/2 inch if memory serves. I modified the front aluminum (rectangular block) bracket pretty heavy I remember. I opened the holes of the rear bracket to allow catching it with original holes in manifold.

[TJ Hopland]

My idea with the dual groove if it exists is that maybe the new groove will be further forward so you could then space the compressor back which sound like it would be a lot easier than moving it forward.

If there is enough 'meat' in the front bracket to allow the proper position maybe present that as an option to the machine shop too.  It may be easier (& cheaper) to machine the bracket than a pulley.

[TJ Hopland]

Who was it Olds and or Buick that also had a dual groove?   Maybe snooping around some of their forums or parts sites will turn up something?

[V63]

It really wasn't major surgery to move it forward. I used a 4" hand grinder to massage the brackets. I wouldn't hesitate to do it again.

[Chad Speer]

I believe the new aluminum A6 compressor you have is actually a drop in for GM EXCEPT Cadillac.

I bought one of those and I had to move the compressor forward 1/2 inch if memory serves. I modified the front aluminum (rectangular block) bracket pretty heavy I remember. I opened the holes of the rear bracket to allow catching it with original holes in manifold.

Okay, that gives me a new direction to consider.  I think I could use some spacers between the rear bracket and the compressor to move the compressor forward without modifying the rear bracket.  This compressor is so much lighter that I don't think using spacers should be a problem with those beefy 3/8"-16 bolts.  Then I would just need to modify that front bracket.  That might be easier, and would definitely be simpler than modifying the pulley.  I found a front bracket on eBay just now, so I went ahead and ordered that so I can play with it.  This is no show car, but it's nearly all original and in very nice condition at 58,000 miles.  I'd like to retain the ability to return it to unmodified condition in the future.

[Cadman-iac]

Who was it Olds and or Buick that also had a dual groove?  Maybe snooping around some of their forums or parts sites will turn up something?

Well I can tell you that the 64 Olds with the 394 has a dual belt on the A/C  and alternator.
I don't know if it's permitted, but here's a picture of mine.

Rick

["Cadillac Kid" Greg Surfas 15364]

FWIW the double belt systems use belts that are narrower with a different pitch than the single belt systems
Greg Surfas

[Chad Speer]

FWIW the double belt systems use belts that are narrower with a different pitch than the single belt systems
Greg Surfas

Thanks, Greg.  That narrows down my options, but I think it's still manageable.  I've read dozens of your posts on the Cadillac air conditioning systems.  I've learned a lot from you.

[V63]

I found an image I have of the aluminum A6

[Chad Speer]

Just an update on this project from last year.  I was able to shape a new front bracket from 1/8" steel angle, and just used spacers between the compressor and the unmodified rear bracket.  I'm currently trying to find a leak that's preventing me from holding a vacuum, and I suspect it's the o-rings on the fittings on the back of the compressor.  I added a new set of o-rings from Old Air Products when I bought the Pro6TEN, but now I'm thinking I changed all but those two big o-rings last summer.  That's what I get for dragging this project out.  My driver window shattered not long after my last post, and it took a while to source a NOS window in that green tint.  I'll try to post some pictures when I have it all working again.  Looking forward to some cool summer driving this year.

[TJ Hopland]

Is the receiver (tank thing) the universal type where the center fitting thing can pivot around to different positions?  If it that type what ever they used for a seal doesn't seem to work with vacuum.  When I did mine several years ago now with one of those kits it would not hold vacuum very well. 

I just got frustrated and charged it anyway and I think it went like 3-4 years before needed a slight top off.  I sent them a message asking if anyone else had noted that and suggested they add that to the notes for the part but as far as I know they never did.   

["Cadillac Kid" Greg Surfas 15364]

Chad,
The proper way to leak check ANY refrigeration or AC system is under pressure. All the joints and seals are designed to hold the pressure the system will be under. Under vacuum the O rings are actually pulled away from their sealing surfaces so they can leak. Pressurize the system with either a bid of refrigerant or nitrogen up to about 50 psig and then using a (now relatively in expensive) electronic leak detector or even soap bubbles on each of the joints you can find out exactly where the system is leaking.
Greg Surfas

[Chad Speer]

TJ - that is the design I have.  I'd be fine with an occasional top off, but now seems like a good time to try to get leak free.  From your description, I may already be good enough.

Greg, thanks for those tips.  I've only worked on my own residential and marine/RV systems with brazed joints or flare fittings.  I always vacuum a system down below 500 microns, but I hadn't considered the o-ring issue.  I'm going to get a nitrogen tank so I can check it under pressure.

[TJ Hopland]

I think its a decent design for pressure its just not especially good for vacuum.  I don't know where my leak is, its way to slow to detect. Plenty of places it could be leaking over that many years.  It was still working when I topped it off I just could hear the compressor cycling when I wasn't expecting it to be.

Greg, how bad would a 'leak' from a seal design like this have to be before it would actually cause issues drawing in outside air during the vac before charging process?   Or once the system is vacuumed down does anything that gets sucked in pretty much get sucked back out?  So you just don't want to wait too long between turning off the pump and charging?

["Cadillac Kid" Greg Surfas 15364]

TJ
2 things. If there is a leak under vacuum you might find it impossible to find it. Take a look at the connections using an o ring and they all have a "shoulder" on the tube that the o ring presses against when under pressure to fully seal the joint.
Secondly, any air that enters the system while under vacuum contains moisture, and with the lows of Psychrometrics (the study of the properties of an air/vapor mixture), there is an enormous vapor pressure differential allowing a great deal of moisture to enter.
Greg Surfas

[smokuspollutus]

Forgive if it was mentioned already, but it may be worth your while to source a new fan. I'm sure the impact of the clutch to the fan blades was pretty violent and that could be enough to throw your fan out of balance. May be cheap insurance against an early water pump replacement.

[Chad Speer]

Forgive if it was mentioned already, but it may be worth your while to source a new fan. I'm sure the impact of the clutch to the fan blades was pretty violent and that could be enough to throw your fan out of balance. May be cheap insurance against an early water pump replacement.

I appreciate you mentioning that.  There were just a couple of small dents on the blades, and it seems to run smoothly, but I don't want more trouble down the road.  I'll see what's available.