Correct AC compressor pressure?

e30cabrio · 06:04 PM

My 4/90 325ic was in a front end collision, and my fully functioning ac was dismantled in order to replace the core support. It was recharged and worked for a day.

Now it blows hot. The compressor engages, there are no bubbles in the sight glass and the steel lines get cold to the touch.

The tech said the compressor was outputting 500 psi and I have been told that is too high. What should the pressure be & if too high what does that indicate?

Thanks

coolbear1 · 03:13 PM

It sounds like you have a restriction in your system, Probably at your expansion valve or maybe receiver drier.

It also could be Non-condensible, (air) from not pulling a proper vacuum on the system prior to charging it up.

Air does not condense into a liquid in a air conditioning system, therefore it just sort of takes up space like a big bubble and causes the high side pressure to go off the chart.

In your case I would loOK for a restriction, especially if your low side pressure is low or goes into a vacuum.

I assume you are using 134a refrigerant and your electric fan is functioning, in which case your high side will be in the 225-275 range. Its not unusual to see it a little higher, but 500 will destroy your compressor in short order.

Don't run it until you find the problem.

I don,t know if a 1990 was originally 134a, but if you have a R-12 Bher-Bosch compressor it has a sponge loOKing material in it, that heat, and 134a will break down and send all through the system causing the problem you describe.

If you have the Seiko-seiki, or most other brands you might be OK.

I know this is a lot more information than you asked for, but it is sometimes a complicated subject when you are dealing with a retrofitted car.

Good luck.

e30cabrio · 05:35 AM

Thanks for all the info. I am in Mexico where r12 is readily available and they recharged with r12. They replaced the o rings and it worked for a day.

Is the pressure the same in r12 systems?

Thanks

coolbear1 · 08:27 AM

No, it is lower.
165-220.
Is your electric fan working when the a/c is on?
First make sure, Then, make sure it is not overcharged.
Adjust the charge down until suction pressure starts to drop.
(let gas slowly out of the high side). If you can get ahold of a reclaim cylinder, pack it in ice and pull a vacuum on it. You can release your refrigerant into it.
Put a thermometer into one of the vents as you release the refrigerant and watch for the temperature to drop. If you can get 15 degree f. or better, drop in temperature from air in to air out, all is good and it didn't cost you anything.
If not and R-12 is readily available, and you are sure you don't have a leak, drop the charge, replace the expasion valve and the receiver drier.
Pull a good vacuum on the system and replace with new refrigerant.
Good luck.
Hope it works out.

e30cabrio · 10-18-2005, 10:52 AM

Fan working, yes. I have been meaning to take the car back to the shop that fixed it since Friday and just have not had time (plus not wanting to relinquish it again) and I am glad I didn't because this latest info should be benificial. Thanks so much for your time and input.

e30cabrio · 10-18-2005, 06:53 PM

Well it appears the new receiver dryer I got was defective. Can anyone tell me which Ford/GM/Dodge current unit will fit? I do not have time to wait for parts from Germany (from BMW) or the US.

Thanks

coolbear1 · 10-18-2005, 09:28 PM

Me again, can't help you with the domestic replacement thing. No need for that here, aftermarket replacements for the BMW reciever drier are available here locally. Made in Mexico I think.

I'm currious, was the reciever drier stopped up?

e30cabrio · 10-19-2005, 08:05 AM

It seems it was dried up pre install. Any idea who makes the unit & what the p/n is?

coolbear1 · 10-19-2005, 08:36 AM

Go to; www.drivewire.com

Everthing you need to know about receiver driers for most cars.

e30cabrio · 10-19-2005, 10:35 AM

Thanks. I found it on ********.

e30cabrio · 10-19-2005, 03:59 PM

I just got back from the shop and they insist the problem is the expansion valve at the evaporator. Does it make sense that it would die from opening the system? I really do not want to have to wait for a month, buy a 1600 peso part & have to rip the dash open.

Thanks

coolbear1 · 10-19-2005, 11:08 PM

Yes, unfortunatlly the expansion valve is basically a restriction that is designed into the system. It meters the liquid refrigerant into the evaporator, so if you have to open the system any contamination that ether gets in or is dislodged sometimes ends up there.

I hate to place blame because I don't know all of the particulars, but,
Honestly, it sounds like the system wasn't cleaned up properly or they installed a dirty used condenser, or maybe used reclaimed R-12 that was contaminated.

Make sure you replace the receiver-drier and pull a good vacuum.

If you can get it, tell them to use virgin r-12, if you have to use reclaimed refrigerant, RUN IT THROUGH A FILTER DRIER!
You don't know where reclamed Freon has been or who it slept with.

Seriously, If you don"t clean up the system and replace the drier your most likely to just get more pissed off when it breaks again and you have to spend more money on it.

Is it hot year round where you are in mexico?

I hope you are not in the path of whatever they call the latest hurricane thats out there.

I'm in Florida.

Thinking about building an ark.

Rounding up a few animals.

Two by Two.

Did you have to replace the condenser from the accident damage?

e30cabrio · 10-20-2005, 05:21 AM

I am inclined to agree with you, that the guy that recharged the system, (with new r12) did not properly clean the system. I know he did not replace the receiver/dryer. (I saw the new one I brought at the body shop yesterday) The system worked great for a day. I am upset because the BMW parts are not available here, have to come from Germany which takes 2-6 weeks, and are really expensive (the expansion valve is 1633.00 pesos about 148.45) I can get the entire evaporator, valve and receiver/dryer delivered here for 204.98 I really don't want some mechanic with no experience in e30s taking my dash apart. It has no rattles and for a 15 year old convertible thats amazing!

Here are a few threads I made about this adventure the first is from begining to end and the second is a condensed version:

http://www.e30tech.com/forum/viewtopic.php?t=12905&postdays=0&postorder=asc&start=0

http://www.e30tech.com/forum/viewtopic.php?t=13839&highlight=

coolbear1 · 10-20-2005, 08:39 AM

I know what you mean, I have an 88 325i Convertable with only 97k miles on it, a 93 325I 4 door with 97k miles and a 98 Z3 roadster with 45k miles, all red, and all still like new, I wont even let anyone change the oil on them, much less do anything complicated.

I have owned BMW's since I bought my first one new in 1985, and I learned my lesson after a while.... If you are going to own them you had better learn how to work on them. Not only because of the price of repairs, but the expertise from various mechanics, and repair shops varies greatly.

It seems I had my car not fixed, more than I had it fixed. But they damn sure didn't mind charging me the same in ether case. I got tired of paying to send them to school working on my car. I figured If I was going to pay for trial and error mechanics, it may as well be me making the mistakes.

Have you tried WWW.ACSOURCE.COM?

They have the aftermarket parts you need , and they also have a Mexican division WWW.AUTOCLIMAS.COM.MX

As far as I can tell (I can't read spanish) The Mexican division doesn't have BMW parts.
I don't know much about them, and how it works (getting parts to Mexico from the U.S.) but maybe they can get you the BMW aftermarket parts from the U.S. cheaper and quicker.

coolbear1 · 10-20-2005, 10:30 PM

Threads would not open.

http://www.e30tech.com/forum/viewto...asc&start=0
http://www.e30tech.com/forum/viewto...&highlight=

e30cabrio · 10-21-2005, 04:04 AM

http://www.e30tech.com/forum/viewtopic.php?t=12905&highlight=

http://www.e30tech.com/forum/viewtopic.php?t=13839&highlight=

Sorry

coolbear1 · 10-21-2005, 09:04 AM

Wow, someone really banged it up. The same thing happened to my 85 not quite that bad, but the insurance company totaled it.

By the way, my 88 325i is almost identical, only differance is I added Zinder body kit and BMW low pro- 6 spoke wheels. Sort of like what an M3 would look like if they made it in a cabrolet.

I've got it for sale because I bought the Z3.

e30cabrio · 10-21-2005, 01:56 PM

I fixed her for less than 4k (when all was said and done about 1500.00 for the body shop) including driving 1400 miles in my Suburban @ about 13mpg and my Wife's shopping in San Antonio, Tx.

Labor here is practically free. There are lots of road hazards and I have killed my oilpan 3x, in the states it was close to 500.00 for labor, here I paid 600 pesos (55.00)

coolbear1 · 10-21-2005, 09:44 PM

Good deal, well I'm outa hear unless I can be of help.

By the way I've been In the Comercial and Residential Air conditioning and Refrigeration business for 30 years.
Not automotive though, except for myself.

Let me know how the a/c thing goes.

e30cabrio · 10-21-2005, 09:56 PM

The Mexican arm of the site you gave me has the parts I need for 650.00 pesos delivered. Thanks so much! I'll let you know how it worked out when I get them installed. Thanks so much for your help!