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I’m exploring re-installing air conditioning in my car. Car is a ‘78 with a B35 and 5-speed out of an ‘89 635 CSi. Everything in the engine compartment was removed when the swap was done years ago. Everything on the cabin side of the engine compartment is still present. My interest is in regaining functional AC for a reasonable amount of money. It doesn’t have to be the best possible AC, as even decent AC is a lot better than none, and I don’t wan tto spend mega-$ for it. To that end, while a modern parallel-flow condenser is more efficient than an old one, I have an old one with fan that is good, and that’s good enough. I think I can do this for like $800 in parts, and good enough for $800 is preferred to great for twice the money.

I can DIY modern barrier lines with O-rings with this kit:
https://vintageair.com/reduced-barrier- ... ith-drier/.

Making those lines would require a crimp tool like this, which Vintage Air loans out:
https://vintageair.com/reduced-barrier- ... ith-drier/.


I have flare fittings at the firewall, which would require these adapters to attach modern lines:
https://www.summitracing.com/parts/fss- ... eplacement

I would need a new, R134a-friendly expansion valve, like this:
https://www.acsolutions.co/collections/ ... 4511372077

New Sanden compressor, bracket kit and belt, etc.:
https://www.acsolutions.co/collections/ ... 28-e24-etc

I may need a BMW accessory bracket to support the compressor (p/n 64521284953) but I don’t think so, since my engine is from 1989.

How does the condenser mount? Does it just bolt to the front of the radiator core?

What have I not thought about that I will need to consider? Are there any more small parts?

Where do I wire the fan into the body harness?

Once everything is installed, how do I know how much refrigerant to put in?

Oh man, there's a lot here. I may not finish tonight, but I'll pick it up later if I don't.

Theotherotter wrote: Fri Jul 18, 2025 7:41 pm I’m exploring re-installing air conditioning in my car. Car is a ‘78 with a B35 and 5-speed out of an ‘89 635 CSi. Everything in the engine compartment was removed when the swap was done years ago. Everything on the cabin side of the engine compartment is still present. My interest is in regaining functional AC for a reasonable amount of money. It doesn’t have to be the best possible AC, as even decent AC is a lot better than none, and I don’t wan tto spend mega-$ for it. To that end, while a modern parallel-flow condenser is more efficient than an old one, I have an old one with fan that is good, and that’s good enough. I think I can do this for like $800 in parts, and good enough for $800 is preferred to great for twice the money.

Got it. You accept that you won't have 36F air coming out on 110F days in stop and go traffic because you don't want to spend 3 grand on the thing. I fully understand.

I can DIY modern barrier lines with O-rings with this kit:
https://vintageair.com/reduced-barrier- ... ith-drier/.

Looks like a nice kit, I probably should know, but I don't, will the threads attach to the flare fittings on the evaporator? And remember you will still need the copper washers inbetween the flare fittings.

Making those lines would require a crimp tool like this, which Vintage Air loans out:
https://vintageair.com/reduced-barrier- ... ith-drier/.

Not seeing the crimp tool, but that's no biggie.

I have flare fittings at the firewall, which would require these adapters to attach modern lines:
https://www.summitracing.com/parts/fss- ... eplacement

That's not how I think of O ring fittings working, but I'm probably missing something here.

I would need a new, R134a-friendly expansion valve, like this:
https://www.acsolutions.co/collections/ ... 4511372077

Should work ok, not expensive but I haven't heard of the expansion valve being the problem on conversions. Then again, 45 year old expansion valves are always suspect.

New Sanden compressor, bracket kit and belt, etc.:
https://www.acsolutions.co/collections/ ... 28-e24-etc

Not cheap, but they get very good reviews. If you have it, a big if, and if you have the bracket and if it bolts up, I'm a huge fan of the E12 swashplate compressor. Smooth, quiet, long lasting and works well. Not everyone agrees and apparently they aren't happy about an overcharged system.

I may need a BMW accessory bracket to support the compressor (p/n 64521284953) but I don’t think so, since my engine is from 1989.

How does the condenser mount? Does it just bolt to the front of the radiator core?

The condenser attaches to the core support and the fan attaches to it IIRC.

What have I not thought about that I will need to consider? Are there any more small parts?

Where do I wire the fan into the body harness?

There's always more that you don't think of. There should be wiring present for the fan, and while the wiring is probably adequate, the fuse is marginal. Especially if the fusebox is already showing signs of melting consider a new blade type fuse with a wire coming off the battery positive terminal . However I really don't like the crappy 530i aux fan, the one that came on 528i's and E28s is much better. Significantly larger, 2 speed, much quieter on low speed and really puts out some air on high speed. I'm not saying it has to be that fan, but I would look to a larger, later fan which would either come set up for 2 speeds or that you would make into a 2 speed fan.

Once everything is installed, how do I know how much refrigerant to put in?

I would really look to a parallel flow condenser, they're not that expensive although more work to mount than a stock item. And a less than stellar 47 year old condenser isn't going to be great. Remember what A/C does, it moves heat from inside the car to outside the car, it's a heat exchanger system. 530i's didn't have great A/C when new with R12, so now with R134a it's definitely going to be lacking. I know you said you want something, it doesn't have to be great, but if you're looking at $800 consider another couple of hundred for an upgraded condenser and fan.

Also, I've never used it, but there are many reports of people using air duster for refrigerant. R152 or something, lots of thread on Mye28 and elsewhere about it, especially older domestic cars. I have not used it, but I've read it's the next best thing to R12, better than the hydrocarbon refrigerants and much better than 134a. Charging it. You're going to have to wing it. Watch the sight glass and think low at first. You can always add more, it's better to undercharge than overcharge. Also don't forget the correct oil in the mix.

Summation, a parallel flow condenser, an upgraded 2 speed fan and look into a better refrigerant.

I have build systems using nothing more than the OE evap box and installed a 2 speed aux fan on my Datsun, AKA Infiniti QX4.

Pic of the fan semi installed and link to the thread. https://forums.nicoclub.com/topic616904.html

Thanks, Mike - that’s a very helpful response.

re: adapting O-ring hoses to flare fittings, AC solutions gave me a link to something for that. I may have included the wrong link in my post, but it’s something I can find out. Good point on the copper washers.

I could use an original E12 compressor, but it seemed better to me to use a new compressor.

I hadn’t yet thought about the wiring. I am assuming that the body and engine harness as they are will support the needed functionality.

The condenser and fan I have are from a 528i. I’ve since found links to a modern parallel-flow condenser that is cheap and fits in an E12, so it’s tempting to ditch the old one and use that. But cost creep.

Didn’t excpect to see a nico club link on a BMW forum. I’ve never been on it but I have a ‘93 Sentra SE-R that I’ve had since new and I was aware of it when the site was created.

If you don't have Rob Seigel's A/C book, I really recommend it.

Unless you have an OEM condenser the bracketry is going to need some work. You'll also not likely reuse an OEM fan - the current draw on an old OEM fan with original bearings is likely to be crazy-high, mine was pulling north of 25 amps at startup and routinely melting the fuse. Test the current draw before committing to using it. I think mine was at 21.5 amps running. Modern fans with new bearings and contemporary magnets are a big upgrade and if you don't want to fuss with bracketry, they are lightweight enough to mount with zip-ties directly to the condenser.

My refresh is documented here:

https://www.firstfives.org/phpBB-3.2.1/ ... 546#p33546

I used a thermal relay in the fan circuit. I try to keep things stock, but this is something I installed before the aux fan replacement.

I used flare-to-O-ring adaptors, but I kept the stock drier arrangement, which has a sight glass. A lot of newer driers don't have them. Of course you'd need an R-134a adaptor for the service fitting. And you'll need to install a high-side port somewhere.

If you're using a basic set of gauges you can figure out the charge using tables. Siegel's book walks you through that.

You'll have the evap out to replace the expansion valve, which is good so you can give it a good flush along with the cabin hardlines, which may not have been plugged at the firewall.

I think the parallel flow condenser is a good call for running R-134. The serpentine condenser works better with R-12.

By the way, no need to buy the brand name beadlock crimp tool if you don't already have one, I bought a knock-off from Amazon and it worked great. Not a tool to be in heavy use.

It's a big project but working A/C is a real plus on a car that's likely to get most of it's use during warm months.

Thanks - great info. I’m not familiar with Rob Siegel’s book, so I’ll look into it.

With my wrenching priorities, I won’t have time to do much of anything on this until mid-fall, so if it happens it’s going to be next year. This is my backup car for a rally in the Appalachians in the fall, but I don’t need AC for that.

528i condenser/fans are a big step up from 530s. 2 speed fans that are much larger, quiet on low and airplane take off level on high, and an improved condenser, which is better than the 530, but still not up to modern standards. Depending on how much of the 528i parts you have you might need additional wiring, or not.

That setup might be ok with 134a. Not great, but ok.