A/C Compressor Upgrade

Post your E12 technical questions and comments here. Please, no off-topic posts.

Moderators: Mike W., Pierre

User avatar
528i-1981
Posts: 64
Joined: Wed Feb 07, 2018 5:50 am
Location: Boston North Shore, MA

Re: A/C Compressor Upgrade

Post by 528i-1981 » Tue Jun 12, 2018 9:12 pm

Gents - My AC blows cool-ish, let's say "tepid" - definitely something going on, but not cold. The Haynes manual is really sparse on the AC - a basic diagram of the components and the admonition to get thee to a refrigeration engineer with any questions. So my first hope was that a simple recharge would get me back in business, but I'm not sure if the PO has switched to 134a or if I'm still on R12. I inspected the system quickly from above and saw the dreaded red hose connecting the drier to the condenser. So I've got work to do.

First question - how do I verify whether the system is R12 or R134a?
Second question - evidently there's at least some refrigerant in the system. How do I determine the level?
Third question - is there a way to change out the hose without evacuating the refrigerant?
Fourth question - can I check/top off the compressor oil without removing it?

I know from Mike W's excellent FAQ that the drier needs to be swapped out during an R134a conversion - but the current drier looks original to me, and the red hose (with excellent patina) seems to suggest this might still be R12. It could also have been a hack conversion, but the compressor is still working, quietly at that.
(oo=00=oo) Eric
1981 528i 5-speed

PatinaBeforePolish
Posts: 180
Joined: Sun Jan 18, 2015 1:22 pm
Location: Baltimore, Md.

Re: A/C Compressor Upgrade

Post by PatinaBeforePolish » Wed Jun 13, 2018 6:20 am

Good to know about the R12, I was considering doing the same conversion to R134 and a parallel condenser. If you switched to the parallel condenser, how were you going to mount it to the car? And the fan to the condenser? The stock unit has the brackets spot welded to the condenser frame.
78 F150
79 528i
81 528i parts car
01 540i
86 944

User avatar
Lock
Posts: 192
Joined: Sun Oct 04, 2015 1:51 pm
Location: San Jose, CA
Contact:

Re: A/C Compressor Upgrade

Post by Lock » Mon Jun 18, 2018 11:37 pm

528i-1981 wrote:
Tue Jun 12, 2018 9:12 pm
Gents - My AC blows cool-ish, let's say "tepid" - definitely something going on, but not cold. The Haynes manual is really sparse on the AC - a basic diagram of the components and the admonition to get thee to a refrigeration engineer with any questions. So my first hope was that a simple recharge would get me back in business, but I'm not sure if the PO has switched to 134a or if I'm still on R12. I inspected the system quickly from above and saw the dreaded red hose connecting the drier to the condenser. So I've got work to do.

First question - how do I verify whether the system is R12 or R134a?
Second question - evidently there's at least some refrigerant in the system. How do I determine the level?
Third question - is there a way to change out the hose without evacuating the refrigerant?
Fourth question - can I check/top off the compressor oil without removing it?

I know from Mike W's excellent FAQ that the drier needs to be swapped out during an R134a conversion - but the current drier looks original to me, and the red hose (with excellent patina) seems to suggest this might still be R12. It could also have been a hack conversion, but the compressor is still working, quietly at that.
If you have the red hoses you most likely have R12 because R134a will just seep out of them. But then the conversion could have been a lazy job.

It's hard to tell the age of dryers because OEM and aftermarket ones pretty much all look the same. Their position above the exhaust and with exposure to road dust mean they all look equally dirty. Also, unlike the expansion valve which contains a little bit of refrigerant gas, and the R134a barrier hoses vs R12 cheese grater hoses, the dryer isn't specific to the gas used.

1. R12 and R134a fittings legally have to be different. Here's a chart for the sizes;
https://www.epatest.com/609/manual/manu ... c461181328
2. Get a ac manifold gauge set and check the pressures when it's running, the difference between what you should have and what you do have will show you how much is in there. According to this guide, R12 should be between 25-40psi on low and 200-225psi on high.
http://www.aa1car.com/library/ac_recharging.htm
3. No way to change out the hose without evacuating first. You can take it to a shop and have them just evacuate your system so that you can take it home and work on it.
4. You can top off the oil by either using an inline oil injector on the fill hose, or a can of oil refrigerant oil itself. But again you can't see what's inside the system without evacuating it first.

My system was tepid bordering on useless on a mild day, the pressures were low, and the sight glass was foamy so I knew it had some R12 in it. I have the user manual and near the back it said the car took 2.2lbs or so of gas (I think), so I got two 12oz cans and added them in, using both the pressure and the sight glass to monitor when it was full, and stopped when it was good. It cools really well, the air coming out the center vent is about 40F no matter the weather. After six weeks the pressures are the same so it was likely just never recharged for years and it seeped out the red non-barrier hoses.

As for the parallel condendser installation, the e30 guys generally get lengths of metal and drill holes in them in the right spots. Just google "e30 parallel condenser".
1979 528i 5-speed conversion G260/6
1979 Honda CX500

User avatar
528i-1981
Posts: 64
Joined: Wed Feb 07, 2018 5:50 am
Location: Boston North Shore, MA

Re: A/C Compressor Upgrade

Post by 528i-1981 » Tue Jun 19, 2018 5:55 am

Grateful for this, Lock.

So the uncertainty remains whether the refrigerant currently in the system is R12, or if a lazy and non-compliant conversion has taken place (i.e., no conversion stickers, original R12 fittings and hoses, etc.). Seems that if I want to be certain before risking my compressor by potentially mixing refrigerants, I need to positively ID the refrigerant.

Refrigerant gas identification instruments are very expensive. Has anyone used an oil identification kits? This kit claims to be able to identify polyol ester oil. If my system tests positive for the ester oil, it's got (at least some) R134a in it.

https://www.ebay.com/itm/RECTORSEAL-OIL ... Swo3pWdNvc

Seems to me that if refrigerants had been mixed the compressor might be noisier, but that's not solid enough ground to stand on.
(oo=00=oo) Eric
1981 528i 5-speed

cory58
Posts: 73
Joined: Thu Aug 25, 2016 8:49 pm
Location: Charlotte, NC

Re: A/C Compressor Upgrade

Post by cory58 » Thu Jun 21, 2018 8:41 am

PatinaBeforePolish wrote:
Wed Jun 13, 2018 6:20 am
Good to know about the R12, I was considering doing the same conversion to R134 and a parallel condenser. If you switched to the parallel condenser, how were you going to mount it to the car? And the fan to the condenser? The stock unit has the brackets spot welded to the condenser frame.
Rob Siegel (aka The Hack Mechanic) did a great series of articles last year on adding AC to his early E24. It was called "Conditioning the Shark," and included installation of an aftermarket condenser. If you are a BMWCCA member, the weekly series is available on the club web site.

Cory
Last edited by cory58 on Thu Jun 21, 2018 9:09 am, edited 1 time in total.
1977 530i
1988 320i Touring (euro)
1992 325i Cabrio
2015 328i (wife's car)
2001 325i (R.I.P., still missed)

cory58
Posts: 73
Joined: Thu Aug 25, 2016 8:49 pm
Location: Charlotte, NC

Re: A/C Compressor Upgrade

Post by cory58 » Thu Jun 21, 2018 9:08 am

Some things I've learned from dealing with AC problems on my old Bimmers.

1. If you don't know what refrigerant you have, that also means you don't know what oil you have. I can't remember the names of the different oils, but the main oil that was used with R12 is not compatible with R134. The only thing to do if you don't know what you have is to evacuate the system, dump the oil from the compressor, clean out the system and start over. I'm not an expert, but I have no idea what's been done to my E12 over the past 40 years and would rather plan out a larger project at one time than deal with the frustration of chasing small problems forever.

2. Old systems with the R12 hoses will hold R134 but leak out slowly. I had a quickie conversion was done on one of my E30s back in 2007 and it's still working fine with the original hoses. I have to put a small can of 134a in each spring and sometimes another half can later in the summer.

3. The R12 o-rings and compressor seals are also not compatible with R134a. They will eventually disintegrate from the R134a. Generally, black o-rings are R-12 only and green o-rings will work with both R12 and R-134a. I bought a euro Touring model E30 a few years ago because it had working factory AC. It also had a quickie conversion sometime before I bought it. After the first year one of the old o-rings failed. I fixed that and replaced the drier (required whenever you open up the system). It worked great again for a few months and then a seal in the compressor failed. Now it's waiting for a more complete conversion (compressor, condenser, hoses, o-rings).

Some people dis them online, but I have been happy with the gauge set and evacuation pump from Harbor Freight. The only problem I haven't figured out is that the low side port on my E12 is so close to the side of the drier that I cannot connect the gauge set. Thankfully my E12 AC has worked great with just an R134a recharge each spring. I have a charge-only hose with a smaller low-side fitting.

Cory
1977 530i
1988 320i Touring (euro)
1992 325i Cabrio
2015 328i (wife's car)
2001 325i (R.I.P., still missed)

User avatar
528i-1981
Posts: 64
Joined: Wed Feb 07, 2018 5:50 am
Location: Boston North Shore, MA

Re: A/C Compressor Upgrade

Post by 528i-1981 » Mon Jul 23, 2018 5:46 pm

Well, I decided that, based on the other things done to the car by the PO, there was only a minimal chance that he had converted to R134a and left all of the original R12 hoses and fittings. I can't be 100% sure, but the drier looks original. The system was blowing about 70 degrees from the top vents, so I deduced that the chances were good overall that the leaks weren't total. So today a 14 oz can of R12 was added (note the passive verb voice here), and the flow through the sight glass looked mostly bubble-free. After a 20 minute drive, the system was blowing at 48.5 degrees F with the engine at 3000 RPM.

I'll monitor over the coming weeks to see if there's a performance loss. I suspect that if 134a and R12 were mixed there would have been a creamy look through the sight glass and I wouldn't have been able to get the performance I did. Is that true?
(oo=00=oo) Eric
1981 528i 5-speed

tlake
Posts: 115
Joined: Wed Feb 03, 2010 6:33 pm
Location: WA

Re: A/C Compressor Upgrade

Post by tlake » Thu Jul 26, 2018 3:52 pm

528i-1981 wrote:
Mon Jul 23, 2018 5:46 pm
Well, I decided that, based on the other things done to the car by the PO, there was only a minimal chance that he had converted to R134a and left all of the original R12 hoses and fittings. I can't be 100% sure, but the drier looks original. The system was blowing about 70 degrees from the top vents, so I deduced that the chances were good overall that the leaks weren't total. So today a 14 oz can of R12 was added (note the passive verb voice here), and the flow through the sight glass looked mostly bubble-free. After a 20 minute drive, the system was blowing at 48.5 degrees F with the engine at 3000 RPM.

I'll monitor over the coming weeks to see if there's a performance loss. I suspect that if 134a and R12 were mixed there would have been a creamy look through the sight glass and I wouldn't have been able to get the performance I did. Is that true?
Sounds like you fixed it, fingers crossed all the gas stays in there.

cory58
Posts: 73
Joined: Thu Aug 25, 2016 8:49 pm
Location: Charlotte, NC

Re: A/C Compressor Upgrade

Post by cory58 » Mon Jul 30, 2018 4:25 pm

528i-1981 wrote:
Mon Jul 23, 2018 5:46 pm
Well, I decided that, based on the other things done to the car by the PO, there was only a minimal chance that he had converted to R134a and left all of the original R12 hoses and fittings. I can't be 100% sure, but the drier looks original. The system was blowing about 70 degrees from the top vents, so I deduced that the chances were good overall that the leaks weren't total. So today a 14 oz can of R12 was added (note the passive verb voice here), and the flow through the sight glass looked mostly bubble-free. After a 20 minute drive, the system was blowing at 48.5 degrees F with the engine at 3000 RPM.

I'll monitor over the coming weeks to see if there's a performance loss. I suspect that if 134a and R12 were mixed there would have been a creamy look through the sight glass and I wouldn't have been able to get the performance I did. Is that true?
Great result! Stockpile some real R12 and postpone the conversion as long as possible.

To correct one error in a previous post - Exact fit parallel flow condensers are readily available for E30s, so no bracket fabrication is needed. For E12's? I don't know, but my money would be on us having to buy a generic condenser and fab mounting brackets, like Rob Siegel did when adding A/C to his early E24.

Cory
1977 530i
1988 320i Touring (euro)
1992 325i Cabrio
2015 328i (wife's car)
2001 325i (R.I.P., still missed)

User avatar
528i-1981
Posts: 64
Joined: Wed Feb 07, 2018 5:50 am
Location: Boston North Shore, MA

Re: A/C Compressor Upgrade

Post by 528i-1981 » Mon Jul 30, 2018 8:26 pm

Well, there's always a rub, isn't there?

Image Image Image

Low side very high (135 psi), high side low (125 psi), moisture indicator yellow. Yes, the lines are hooked up correctly (red to port on drier, blue to fill port). I'm still getting cooling, but it takes about 20 minutes to get down to around 48 degrees at the center vent at about 83 degrees F ambient. That's just outside the curve. I was going to add some more R12 but now I'm glad I didn't.

So am I correct in concluding that I need to drop the charge and evacuate, and replace the drier? If so, I'll replace the lines, and do everything else you can do with a discharged system.

How bad is it to run the system under these conditions?
(oo=00=oo) Eric
1981 528i 5-speed

tlake
Posts: 115
Joined: Wed Feb 03, 2010 6:33 pm
Location: WA

Re: A/C Compressor Upgrade

Post by tlake » Tue Jul 31, 2018 2:05 pm

cory58 wrote:
Mon Jul 30, 2018 4:25 pm
528i-1981 wrote:
Mon Jul 23, 2018 5:46 pm
Well, I decided that, based on the other things done to the car by the PO, there was only a minimal chance that he had converted to R134a and left all of the original R12 hoses and fittings. I can't be 100% sure, but the drier looks original. The system was blowing about 70 degrees from the top vents, so I deduced that the chances were good overall that the leaks weren't total. So today a 14 oz can of R12 was added (note the passive verb voice here), and the flow through the sight glass looked mostly bubble-free. After a 20 minute drive, the system was blowing at 48.5 degrees F with the engine at 3000 RPM.

I'll monitor over the coming weeks to see if there's a performance loss. I suspect that if 134a and R12 were mixed there would have been a creamy look through the sight glass and I wouldn't have been able to get the performance I did. Is that true?
Great result! Stockpile some real R12 and postpone the conversion as long as possible.

To correct one error in a previous post - Exact fit parallel flow condensers are readily available for E30s, so no bracket fabrication is needed. For E12's? I don't know, but my money would be on us having to buy a generic condenser and fab mounting brackets, like Rob Siegel did when adding A/C to his early E24.

Cory
No need to make special brackets with the Vintage Air condenser. At the top just turn the e12's L clamps the other way, and use the Vintage Air provided flat arms with holes to attach the condenser at the bottom.

tlake
Posts: 115
Joined: Wed Feb 03, 2010 6:33 pm
Location: WA

Re: A/C Compressor Upgrade

Post by tlake » Fri Aug 03, 2018 1:23 pm

I will just add, it's always a good idea to make sure the cooling fins on the condenser are free of dirt. Sometimes they can get caked up with dirt if the fins get sticky due to blown forward coolant from a leaking radiator etc. Gentle cleaning with a toothbrush and mild soapy solution can help.

User avatar
528i-1981
Posts: 64
Joined: Wed Feb 07, 2018 5:50 am
Location: Boston North Shore, MA

Re: A/C Compressor Upgrade

Post by 528i-1981 » Fri Aug 24, 2018 8:00 pm

cory58 wrote:
Thu Jun 21, 2018 8:41 am
PatinaBeforePolish wrote:
Wed Jun 13, 2018 6:20 am
Good to know about the R12, I was considering doing the same conversion to R134 and a parallel condenser. If you switched to the parallel condenser, how were you going to mount it to the car? And the fan to the condenser? The stock unit has the brackets spot welded to the condenser frame.
Rob Siegel (aka The Hack Mechanic) did a great series of articles last year on adding AC to his early E24. It was called "Conditioning the Shark," and included installation of an aftermarket condenser. If you are a BMWCCA member, the weekly series is available on the club web site.

Cory
Siegel published a more complete work as a book this year called "It Just Needs a Recharge" which is available on Amazon. Best $30 I've spent in awhile. It covers almost everything, with a pretty long chapter on how to mount the condenser. It's not trivial, you may need to fashion some mounting hardware if you want to go big, but after reading the book I feel confident I could do it. The book mentions mounting a low-profile, lightweight fan to the condenser using a type of nylon zip-tie through the condenser. The bigger high-throughput fans require brackets, which can bolt to the mounting holes on the universal-fit condenser.
(oo=00=oo) Eric
1981 528i 5-speed

User avatar
528i-1981
Posts: 64
Joined: Wed Feb 07, 2018 5:50 am
Location: Boston North Shore, MA

Re: A/C Compressor Upgrade

Post by 528i-1981 » Fri Aug 24, 2018 8:05 pm

tlake wrote:
Tue Jul 31, 2018 2:05 pm
cory58 wrote:
Mon Jul 30, 2018 4:25 pm
528i-1981 wrote:
Mon Jul 23, 2018 5:46 pm
Well, I decided that, based on the other things done to the car by the PO, there was only a minimal chance that he had converted to R134a and left all of the original R12 hoses and fittings. I can't be 100% sure, but the drier looks original. The system was blowing about 70 degrees from the top vents, so I deduced that the chances were good overall that the leaks weren't total. So today a 14 oz can of R12 was added (note the passive verb voice here), and the flow through the sight glass looked mostly bubble-free. After a 20 minute drive, the system was blowing at 48.5 degrees F with the engine at 3000 RPM.

I'll monitor over the coming weeks to see if there's a performance loss. I suspect that if 134a and R12 were mixed there would have been a creamy look through the sight glass and I wouldn't have been able to get the performance I did. Is that true?
Great result! Stockpile some real R12 and postpone the conversion as long as possible.

To correct one error in a previous post - Exact fit parallel flow condensers are readily available for E30s, so no bracket fabrication is needed. For E12's? I don't know, but my money would be on us having to buy a generic condenser and fab mounting brackets, like Rob Siegel did when adding A/C to his early E24.

Cory
No need to make special brackets with the Vintage Air condenser. At the top just turn the e12's L clamps the other way, and use the Vintage Air provided flat arms with holes to attach the condenser at the bottom.
Which Vintage Air condenser are you referring to that can mount like this? I'm on the fence about replacing my stock serpentine condenser, but dealing with the relocated condenser ports on a universal-fit unit adds some complication. Does your E12 have a Vintage Air condenser and were there any complications locating the hoses/fittings?
(oo=00=oo) Eric
1981 528i 5-speed

tlake
Posts: 115
Joined: Wed Feb 03, 2010 6:33 pm
Location: WA

Re: A/C Compressor Upgrade

Post by tlake » Wed Aug 29, 2018 2:44 pm

It's the 14x20 parallel flow unit. That's the biggest you can fit in an e12 from Vintage Air, and is more than adequate. I used the 12x20. Either way, you don't need any special fabrication, and any slimline fan bolts on the condenser holes provided. As I said, the condenser comes with some holed metal pieces to mount the bottom. The existing e12 L clamps can be turned around and handles the top mounting.

03261-VUC Condenser with brackets, 14” tall x 20”wide x .83” thick

Post Reply