AC ideas and suggestions

[PatinaBeforePolish]

Hello! I plan to refurbish the AC on my 79 528 this winter. It has the original motor and a manual transmission. My goal is to have the system work as well as possible in the factory spec. I don't expect it to make the car ice cold in 110 degree weather and don't want to completely re-engineer the system. Other than a yearly trip to The Vintage in NC, I use the car in the mid-Atlantic area - think humidity!

I have a NOS condenser, expansion valve and dryer and will have hoses made once I decide on the compressor. The original compressor bracket is currently mounted and I have an aftermarket bracket to mount a Sanden, if needed. All other original factory HVAC components are in place and in working order.

My current thought is to have the original Bosch compressor restored and use R12 refrigerant. I've definitely considered the environmental concerns with R12 and am thinking of using it as the general consensus is the system runs a bit cooler. My rational is there's lots of it still out there and why not use it in a new sealed system before careless storage lets it leak into the atmosphere?

Thoughts or suggestions?

Jon

[HB528i]

Go with a new parallel flow condenser it will make a huge difference. I used a wing cell and Layne Wylie bracket with a Sanden 508 but didn’t change the condenser, it is still R12 but only gets down to 43 degrees in SoCal.

[Mike W.]

I second the idea of using the largest parallel flow condenser. The stock 528i one isn't bad, a definite improvement on the earlier 530i ones, but not as good as parallel flow. Obviously make sure the aux fan up front is working well too. The stock compressor is just fine, the system is limited by the condenser and evaporator, not the compressor. And R12 is an excellent idea.

I had the A/C working well on my first E12, a 79 528i, and in the desert, on the road, admittedly not in town, it would blow 42F air and keep us cool. The compressor was cycling and the blower was one notch below max.

[tlake]

If you have access to R12, stay stock. If you want to use R134a, get a parallel flow condenser, they aren't expensive and the Vintage Air unit mounts easily. A new slimline fan to go with the new condenser would be good too.

[PatinaBeforePolish]

Thanks for all the suggestions. I now have about 5 lbs. of R12 so I’m committed on that. I also decided on adding dynamat or similar insulation. I did that in my 78 f150 which made a noticeable difference.

[528i-1981]

R12 is great.

I do think replacing the condenser is a sensible move. Parallel flow condensers are far more efficient. I know you have the NOS condenser and that's a tempting morsel. And also, the fan mount brackets mount to the factory condenser which has a beefy frame. You'll need to engineer around that if you use an aftermarket condenser. At that point, you may conclude as I did that the stock aux fan should also be upgraded. The aux fan in my E12 was weak and was drawing north of 25 amps so give it a thorough bench testing before reusing it. New fan motors are much more advanced and are quieter.

So the project becomes larger and more expensive once you move to the parallel-flow, but consider that even with 5 pounds of R-12, it's a 1 kg (2.2 pound) charge. Sometime in the future you really may want to run R-134a, and a parallel flow condenser provides a measure of future-proofing.

If you don't have a refrigerant machine and tank, I recommend you get these. Same for an N2 bottle. I've evacuated my system more than a half-dozen times getting it to where it is.

Parallel flow condensers have smaller channels so the flush is important to make sure there is zero debris in your system. You're replacing the expansion valve, so the evaporator will need to come out of the car. Pressure test it when it's out.

As for hoses, you'll need to deal with a mixed bag of flare fittings and o-ring fittings if you replace the condenser. If you stay stock then obviously you'll only have flare fittings. I've done hoses both ways - I've ordered them from ColdHose custom and I've made my own using a crimper. Hands down the investment in a Chinese-clone crimper was well worth it. Big difference between routing a finished hose with the fittings already on versus snaking a bare hose (that's longer than it needs to be) into position and then trimming and crimping it. Torsion on the hose can make lining up the fittings on a pre-made hose a bear. If you crimp your own fittings, you can do that with the hose already in place and get the fitting exactly where you want it.

Rob Siegel's book is an essential resource, if you don't already have it. Some things that I learned that you might already know: buy way more copper crush gaskets than you think you'll need. Be attentive to the drain plugs on the Bosch axial compressor and be sure they're sealed well with a fresh gasket before charging the system. A refrigerant sniffer is also very handy - a tiny bit of refrigerant added during N2 testing is detectible and a huge time saver. Fluorescent dye in the mineral oil is also a big help, just make sure your engine bay is cleaned of any past dye stains before starting.

Also, by way of mission creep, if you want to spiff up the paint on the right side of the engine block, there's no better time. ; )

Enjoy the project, there's nothing like cold AC.

[Lock]

Seconded - as Eric says, R12 is great. I'm running it in mine with all original setup including original condenser.

Having said that I know my way a little bit around HVAC. I changed filter/dryer and the oil in my original compressor and re-gassed before this summer, and it has been icy cold, even on 110F days, and even with no tinting works fantastically well.

I have to point the vent away from my face because it gets too cold.

[Mike W.]

I have to point the vent away from my face because it gets too cold.

That's what the thermostat operated by the temp dial is for!

Which is also one thing that drives me nuts about newer cars, they run the A/C full blast all the time, then reheat to control temp. Except reheat often doesn't work like it's supposed to. Grrrr.

[Lock]

Man I always forget about that feature, and when I want AC I turn it to COLD, and direct the vents away. It's habit because I'm used to literally every other car I've been in with an AC button for either on or off, which translates to either freezing, or sticky with condensation smell.
To address the original question, I like the Bosch compressor. The only downside is it's big and heavy, and getting the belt on or off is a pain (I unbolt it and lift the whole thing with a jackstand), but is reliable and some report the smaller e28 and e34 compressors are noisy. If your Bosch is still healthy I'd say use it, otherwise a Sanden is probably fine. Definitely consider a parallel flow condensor as Eric suggested.
I was looking into refurbing the Bosch once, and it doesn't look hard, take a look at this thread. Getting parts is the biggest difficulty it seems.
https://rennlist.com/forums/928-forum/1 ... newer.html

[Mike W.]

Agreed, the old swashplate compressor is great, smooth, quiet and effective. And yes, the wingcell on my E28 was always rough, noisy and short lived.

Apparently the much newer Sanden compressors are even better, but I've no experience with them personally, just what my E28 friends tell me.