BimmerFest BMW Forum banner

1991 525i air conditioner not working

7657 Views 12 Replies 6 Participants Last post by  DrCharles
My a/c has not worked since I purchased my car 2 years ago (awful right?) My dad has been working on my car all weekend and we cant seem to find what exactly is not working. He says the compressor seems fine and that it might just be an electrical problem. Any suggestions on what I should be looking for? or links to a wiring diagram because I cant find one online anywhere.
1 - 13 of 13 Posts
Does the clutch engage when you turn the A/C on?

That's the first and simplest thing to do before we get complicated.
Does it have a full refrigerant inside the compressor? Have it check from an air conditioner professional.
air conditioning sun valley
Another cheap/easy way to verify it is not being kept from engaging (the compressor that is), would be to spend the money on a refill can w/ a capacity meter attached to it from a local auto parts store. Green=go ;)
If you follow directions included, you can rule out low refrigerant. Make sure you do not mix old (R-12) and new (R-134a) in case you didn't know. Which basically involves knowing what's in your car now. It's probably posted in manual, or a sticker around the bay if it's been converted already. You're not gonna find the R-12 readily available these days, not without an HVAC license anyhow.
That is a great idea. You can convert the system VERY easily. I learned the AC buiz from my dad, and have done a lot of them. They even sell the kits at the auto stores, same bottles 134 comes in, but it includes the oil and cleaners needed.
R12 is around, but it is like gold, anyone with it is holding onto it for a while.
Another cheap/easy way to verify it is not being kept from engaging (the compressor that is), would be to spend the money on a refill can w/ a capacity meter attached to it from a local auto parts store. Green=go ;)
If you follow directions included, you can rule out low refrigerant. Make sure you do not mix old (R-12) and new (R-134a) in case you didn't know. Which basically involves knowing what's in your car now. It's probably posted in manual, or a sticker around the bay if it's been converted already. You're not gonna find the R-12 readily available these days, not without an HVAC license anyhow.
R-12 vs R-134a

Yeah, I heard from a very trusted source or two, that the incompatibility arises when you mix the two oils. They do not play well together, create foam, and clog screens & orifices. Correct me if I'm wrong. My experience on an old A/C system was to simply convert the schrader valve to accept a normal 134 connection, and fill with 134, vacuum and oil be damned. That thing worked for 5 years for me, and continued for some time from what I heard last. Don't bet on my results, but that's my experience with it.
That is basically the proper way to do it, make sure all the R12 is out, and put new ports on it, they make screw ons, and fill 'er up.
Yeah, I heard from a very trusted source or two, that the incompatibility arises when you mix the two oils. They do not play well together, create foam, and clog screens & orifices. Correct me if I'm wrong. My experience on an old A/C system was to simply convert the schrader valve to accept a normal 134 connection, and fill with 134, vacuum and oil be damned. That thing worked for 5 years for me, and continued for some time from what I heard last. Don't bet on my results, but that's my experience with it.
I disagree... it is not the proper way, but often you can get away with it. For a while. Those quickie retrofits aren't known as "Death Kits" for no reason.

The first problem is, as mentioned, that the two oils are incompatible. I don't believe they cause any clogging or foaming - but since they don't mix, and the old oil is not soluble in (nor circulated by) the R134a, it has to be occupying space somewhere in the system, hopefully staying out of the way and just taking up room that should be filled with R134a.

The correct way is to drain the old oil from the compressor, flush all parts with a suitable solvent (R11 is often used), and of course put in a new receiver-dryer. Assuming that the compressor seals work with the new oil...

Another problem is the o-ring material, and every connection in the system has one, unless it's a really old one that uses flare sealing. I don't remember if the oil dissolves the o-rings or if the R134a attacks them.

To a lesser extent an R12 system will leak a bit faster with R134a because the molecule is smaller and will pass through the wall of the hoses. R134a is now up to nearly $10 a can. If you're going to replace hoses, get the "new" barrier (lined) hoses.

Bottom line is, if it doesn't work to start with and you are willing to chance the "Death Kit", go ahead... but at least vacuum it down, and consider a new receiver-dryer! If you're going to spend significant money on a new compressor, then do it right. I've been working on my own a/c for 20+ years and have never been tempted to take the shortcut even when parts and refrigerant were cheaper.

Just my 2 cents worth :D
That is basically the proper way to do it, make sure all the R12 is out, and put new ports on it, they make screw ons, and fill 'er up.
That is why i said basically, what you said is the exact way, but it does get costly, and for temporary many people are unwilling to try it. The oils will cause foaming under certain situations, i have personally seen it. Sometimes you can get away with the old o-rings, but sometimes not. The o-rings break down when the 134 starts to go through the system, better to replace them, and the dry should be replaced, but again many people are unwilling to do this.

Personally i replace all seals i can, and flush the system, pressure test it, and then hold a vacuum on it for 2 hours after. And on some cars i have done the dryer and a few other parts.

I have dealt with many people that say they don't care about all that, they want it to work for cheap. And others that just say forget it, i have had the windows down this long, i can keep doing it.
I disagree... it is not the proper way, but often you can get away with it. For a while. Those quickie retrofits aren't known as "Death Kits" for no reason.

The first problem is, as mentioned, that the two oils are incompatible. I don't believe they cause any clogging or foaming - but since they don't mix, and the old oil is not soluble in (nor circulated by) the R134a, it has to be occupying space somewhere in the system, hopefully staying out of the way and just taking up room that should be filled with R134a.

The correct way is to drain the old oil from the compressor, flush all parts with a suitable solvent (R11 is often used), and of course put in a new receiver-dryer. Assuming that the compressor seals work with the new oil...

Another problem is the o-ring material, and every connection in the system has one, unless it's a really old one that uses flare sealing. I don't remember if the oil dissolves the o-rings or if the R134a attacks them.

To a lesser extent an R12 system will leak a bit faster with R134a because the molecule is smaller and will pass through the wall of the hoses. R134a is now up to nearly $10 a can. If you're going to replace hoses, get the "new" barrier (lined) hoses.

Bottom line is, if it doesn't work to start with and you are willing to chance the "Death Kit", go ahead... but at least vacuum it down, and consider a new receiver-dryer! If you're going to spend significant money on a new compressor, then do it right. I've been working on my own a/c for 20+ years and have never been tempted to take the shortcut even when parts and refrigerant were cheaper.

Just my 2 cents worth :D
A/C System Check - Simplified

I suppose a more accurate instruction for this issue might have been:

1: Get can of refrigerant w/out oil preferably if converting from R12, with oil if it hooks right up, and apply per it's instructions.

2: If compressor engages, you know it had/has a leak.

3: If compressor does not engage with refrigerant pressure achieved
__A: Compressor clutch and/or circuit needs serviced/replaced.
____1: Check the A/C Clutch electrical circuit.
______a: If there is 12 V or Ground (not positive of the trigger, it will change with light on dash on and off at the connection on compressor
________1) Be sure the clutch isn't simply burned out, or worn out.
__________A: You should be able to visually/audibly tell if the clutch engages watching the front of the compressor,
__________B: Observe while someone switches your, on high, A/C on. (No change= no power, change=circuit good)
______b: If the switch does not occur with refrigerant pressure in place
________1) Check relay and fuse.
__B: May as well plan on the entire o-ring set, drier, the works. Otherwise, what a waste.
4: Decide immediacy vs. long term reliability.
__A: If immediacy is main factor and short term reliability is acceptable
____1: Get more refrigerant, and a stop leak additive.
____2: Enjoy the cool breeze.
__B: If long term reliability is key
____1: Do as Dr. Charles advises.
______a: Get an o-ring kit, and install.
______b: Replace Drier.
______c: Install Compressor
______d: Vacuum system, and verify it holds vacuum for 2 hours.
______e: Apply oil and coolant amounts appropriate to your system. (Maybe someone can state this amount, I will edit here)

Edits?
They do make a refrigerant that is comparable with R12 systems, and R12. It is called freeze 12, and the only place i have seen it is advance auto parts.
R134, cheapest place to get it around me is napa. 7$ a can, everywhere else it is 15-20 for the same size. Freeze 12 is the same price as 134 at advance near me last time i saw it.
I also don't recommend that. Freeze-12 is 70-90% R-134a anyway, and the remainder is another fluorocarbon that allegedly carries the (mineral) oil around the system sufficiently well to keep the moving parts lubricated.
http://www.technicalchemical.com/msds/6030.pdf

What does work as a drop-in R12 substitute is a mixture of propane and butane, commercially available as "Duracool 12a". However, thanks to lobbying efforts of MACS and probably the refrigerant manufacturers, it's illegal for mobile use in 17 states. They scared lawmakers with the specter of "OMG there is 2 lbs of explosive gas that could escape in an accident!" (never mind it blows away on the wind, there is 100 lbs of more dangerous gasoline in the tank, and a leak spewing a mist of oil makes a wonderful flame-thrower when ignited despite the allegedly non-flammable Freon). Also many countries in South America and Australia use hydrocarbon refrigerants and you just don't see the windows being blown out of cars in giant fireballs there!

Anyway, if it's legal in your state <wink>, Duracool works great and requires no retrofitting. It's also cheap since propane and butane are readily available (and have no ozone-depleting potential, if you're concerned). No connection, just a satisfied customer.
1 - 13 of 13 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top