Air Conditioning Problem SOLVED!

[RetiredDoc]

Almost three years ago to the day (service invoice dated May 22, 2008) I picked up the e28 after 11 days in the shop of a local independent BMW shop to address no A/C.

$2,244.85 later, plus tax, I had a new compressor, a new drier, a R12 to R134A retrofit, and an evacuated and recharged system.

Problem was, the cooling of the new system was pathetic. They explained it away with the excuse that R134A isn't as effective as R12, but it's the best we could do. And, after all, BMWs weren't designed for driving in Georgia summers.

Cooling was marginally OK at freeway speeds, but horrible at low speeds, which is where I spend most of my driving time.

Three years went past...., and

today, I went to Pep Boys, and bought a "R-134A Recharge and Measure Kit," thinking that maybe I needed to add some refrigerant.

Hooked up the pressure gauge to the low pressure side, as instructed, and the LOW pressure side read 160 PSI! Thinking I might have hooked up the gauge wrong, I checked, checked, and re-checked. It was correct.

Having nothing to lose, I bled the low pressure side down to 45 PSI just to see what would happen. Lo and behold, brothers and sisters, I now have cold air coming from the dash vents at idle, and almost ice cold air at highway speeds.

[Blue Shadow]

R-134a is supposed to be filled to a weight of about 85-90% of the R-12 charge. Your high dollar conversion guys were idiots and did it wrong overfilling the system with probably more than 100% of the R-12 charge.

Happy Motoring, See you at the Vintage.

[ahab]

Good for you! I've always been skeptical of R134 conversions in a system that was designed for R12 and probably would've believed your guys too but I wheeled Spinedocab's iS for the last few days and got a firsthand experience with one. Admittedly, it wasn't "hot" here, but it was on the high side of plenty warm at 5pm in stopped traffic at the entrance of the GWB on Friday evening, with the sun streaming in, and the air was ice cold. I have to believe that it can hold it's own in the real deal. Glad to hear you're finally happy with yours.

[ckhaw]

That's great news! Funny thing the A/C fellas din know how much to fill an A/C system.

Just wondering, what compressor did they fit into your E28? My 528i is due for a compressor change, pistons are making lotsa noise. Wonder what options have i got, maybe a bigger compressor?

[Brad D.]

If you are going to upgrade anything during a conversion to r134a, upgrade the condenser.

[Jeremy]

If you are going to upgrade anything during a conversion to r134a, upgrade the condenser.

Brad's on the money. A larger compressor won't do much, you need more surface area. Upgrading the aux fan and switching the mechanical fan out for electric helps keep both the cabin and engine temps cool in heavy traffic on hot days as well.

[Snakeyestx]

Just out of curiousity.... what's a normal R12 low pressure reading? I usually chicken out at around 30-35psi which is good and cold, but on days like today when the OBC registered 113 degrees, it couldn't really cope and I suspect I may have it a hair low.

[delorean175]

hey guys my AC compressor making noise, its on my 528e. It only makes it when i rev the engine and drive at higher RPM. It was always a little noisy but it was subtle. Does this sound like the oil is still working its way into the compressor? I did the recharge last week and then i stopped using the AC when it got loud. then yesterday i charged it with an oil charge then only used the AC for about 10 min tops because it still makes noise. It has improved though, it doesn't make the noise every time i rev or drive at high RPM only sometimes. I'm hoping i don't have to replace the AC compressor. I would change it my self but i don't want to loose a full R12 charge. I know AC shops charge a lot for this kind of job. It could possibly be cheaper to buy an AC evacuation system and change out the compressor my self. I have been finding some evacuation systems for 350$. That way i would be able to do future AC work. Anyway its a thought.

[L_N_Love]

Lo and behold, brothers and sisters, I now have cold air coming from the dash vents at idle, and almost ice cold air at highway speeds.

Fantastic! I am spending some $$ now trying to get A/C in mine. Hot as poop here. Just had a leaky condenser replaced but that didn't fix it. Compressor is bad and will be replaced next along with expansion valve.

[LA]

The AC on my '88 E28 had not worked since I got the car in 2007. Last week I put on a new receiver dryer and added oil and R-134a to the press specified with the kit...just colors, red, yellow, and green. It works acceptably in TN's low 90 degree summer heat. So well I'm going to fix the AC on the E23 and the Bavaria!

BTW - E23 guys, ebay has reciever dryers for $46...normally they are around $75. They don't interchange with E28.

[Blue Shadow]

BTW - E23 guys, ebay has reciever dryers for $46...normally they are around $75. They don't interchange with E28.

Azautohaus has the e23 for 18 (behr) or 97 (hansa), I don't know the differences but for cheap, 20 bucks is cheap.

[LA]

BTW - E23 guys, ebay has reciever dryers for $46...normally they are around $75. They don't interchange with E28.

Azautohaus has the e23 for 18 (behr) or 97 (hansa), I don't know the differences but for cheap, 20 bucks is cheap.

Interesting, I returned the $75 unit to the local chain parts store and planned to go the ebay route. Does anyone have experience with the $20 unit from Autohaus?

[CoyoteStarfish]

I have been finding some evacuation systems for 350$. That way i would be able to do future AC work. Anyway its a thought.

Why not make one? My vacuum pump which I also use for reclamation is just an old fridge compressor with 1/4" male flare fittings which are compressed on to the old copper tubes. Just about any high pressure vessel can be used for reclamation. I use an old propane tank, some simple adapters.. Vac the tank, as you would an A/C system. Pack the tank on ice unless you install a condenser after the compressor before the tank. Hook the A/C low side directly to the compressor input. A vac/pressure gauge like the low side gauge on the manifold is helpful on this line but not necessary. Connect the output from the compressor to the center "utility" line on the gauge set and the high side to the reclaim tank. Low side is not used and should remain closed. Purge all noncompressables (atmosphere) from the lines and compressor before opening your tank. Only fill any given tank to 75%-80% by weight.

Keep in mind that if you use a hermetically sealed compressor the entire housing inside is hollow and exposed to the output of the compressor. You must purge the compressor housing with refrigerant unless you devise some elaborate checkvalve system to keep refrigerant locked in the compressor housing at all times. Even then, you'll lose it when you use the compressor to evacuate a system prior to filling.

Ideally, you would have two compressors. One just for vac and the other for reclaim, but you can make one work. I have plans to add an inexpensive descant filter to my setup. Not sure whether to put it on the high or low side of the compressor yet. Northern Tool P/N:156411 filled with silica beads (crystal cat litter). Consult PT charts when playing with this stuff and keep oil comparability in mind if using a hermetic compressor.

Refilling is the reverse of reclaiming. Use hot water instead of ice on the reclamation vessel to help empty the tank, and try to size the tank as close to your charge as possible. Too large and your charge will exist as a vapor making refilling the system difficult, too small and you risk bursting. Happy reclamation!

Also..

[Seeker]

What exactly is involved in a R12 to R134a retrofit, do you use a different compressor and other components and if so what are they?
Thx

[Ken NC]

I thought the conversion from R12 to R134 called for only about 70% of the factory recommended amount of refrigerant (another post said 85-90%)...

Can someone confirm ??

The reason I ask is that I'm working on my AC right now...

[tig]

What exactly is involved in a R12 to R134a retrofit, do you use a different compressor and other components and if so what are they?
Thx

https://acsolutions.bigcartel.com/produ ... pgrade-kit

[Blue Shadow]

I thought the conversion from R12 to R134 called for only about 70% of the factory recommended amount of refrigerant (another post said 85-90%)...

Can someone confirm ??

The correct amount to use is based on the high and low side pressure readings of the system. Because the 134a is lighter it is less weight to use and that amount varies by systems from 75-85%. Can't say for sure without running the numbers, finding out how a particular system handles the process.

If you go below 75% it will most probably be undercharged and over 85% is probably overcharged. Between them you will be as close as you can get without doing by the gauges for the two sides of the system.

[Ken NC]

Thanks for that clarification. I was probably taught to go with 75%, but it's been so long since I've done it myself... the memory thing!