General Air Conditioning Question

**ELVA164** · 10-16-2017, 08:32 AM

Man, reading this thread gave me A/C PTSD. I changed everything in my system except the evaporator and it was the worst job. That said, my A/C is monstrously cold a year later with no refills.

Clark, your system wasn't really "updated" to R134a in all likelihood; most of the time, the adapter fittings are screwed into the hoses, the pressure switch is changed, and sometimes the o-rings are changed in the system.

Since you're trying the R12a (I'm not a fan since CFCs suck, but I get it), you don't have to worry about updating your compressor. If you were going to stick with R134a, a Sanden-type compressor would yield a big improvement in efficiency. Almost all the original E30 compressors were designed to run R12 and aren't as efficient. The condenser helps also as was mentioned.

....ooooh. Something just occurred to me. If he's running R12 again, isn't the pressure switch going to be an issue? Anyone able to comment on this?

**Thecatmilton** · 10-16-2017, 09:21 AM

Originally Posted by Clark Morris

Ok.... Got the thermometer this afternoon..... The ambient temperature on the way home from work was 84 degrees this evening. The center vent readings in stop and go traffic was 80-82..... at 35 to 40 mph was around 70.... and at highway speed was down to no lower than 64 or so.

So, I did order the parallel flow condenser you recommended (and a new Dryer), and the Duracool kit is on order also.

So, where do we go from here?

Clark

Well, your vent temps are quite high. Higher than I expected them to be. What was the outside temperature on the day you got the vent temps?

**Jeffnhiscars** · 10-16-2017, 08:26 PM

He said he had r134 and was thinking of an r12 replacement. Not using PAG w r12 is AC 101 which I was awake for

**ELVA164** · 10-16-2017, 09:06 PM

Originally Posted by Jeffnhiscars

He said he had r134 and was thinking of an r12 replacement.

Not sure if you're responding to my question or not, but that's my thought. R134a runs at different pressures than R12, so the car has the switch modification done. If he goes back to R12, he'll have to revert that part of the system as well, no?

**superj** · 10-17-2017, 12:19 PM

I would imagine so, elva164

**Thecatmilton** · 10-17-2017, 07:20 PM

Originally Posted by ELVA164

Not sure if you're responding to my question or not, but that's my thought. R134a runs at different pressures than R12, so the car has the switch modification done. If he goes back to R12, he'll have to revert that part of the system as well, no?

The switch may have never been swapped. That's another thing to look out for. The PO of my friend's 1991 318i just bypassed it with a paper clip. It's not entirely necessary, think it just protects the compressor by disabling it if pressures get too low.

**Jeffnhiscars** · 10-17-2017, 08:44 PM

The switches are safety mechanisms so get changed out when the theoretical design operating pressure shifts via conversion. However the switches have nothing to with what pressure the system runs at. The problem with many conversions is that they keep the r12 compressor which cannot reach the pressure at which r134 does its job best. This is why people saying r134 isn't as good, are usually thinking of hybrid systems.

do a complete and proper conversion and the results are comparable.

**Clark Morris** · 10-17-2017, 10:20 PM

Originally Posted by Thecatmilton

I wouldn't use PAG oil if r12 has been ran in the system. It gets quite corrosive when it comes into contact with r12 mineral oil.

I would personally use Ester oil as it doesn't have this issue. It doesn't react badly when it comes into contact with the mineral oil. It's also compatible with r12, r134a, and other refrigerants.

Alright gentlemen,

Just to keep me non-confused. My car was converted from R-12 to R-134a many years ago..... The compressor was replaced at that time .... so I assume that the oil is PAG oil in it right now.

I took my car to a repair shop and they have drained the R-134a from the system....

I have obtained the Duracool kit, and from the reading I have been doing I "should" be able to directly replace with the R-12a.... and keep the PAG oil. And I assume adding the little bit for the new Drier and new Condenser?

Anybody objecting to this?

OR... Do I just replace with R-134a again....... I am really trying hard to get this little car to keep up with 90 degree temperatures still occurring in late October.

V/R
Clark

**Clark Morris** · 10-17-2017, 10:42 PM

I think I just answered my own question ( see the link). Unless somebody can give me a good reason not to go to R-12A .. I think I am going to proceed.

http://www.duracool.com/-faq.html

**superj** · 10-18-2017, 07:03 AM

if you already have the duracool kit, run it. no need spending more money.

**aaverhulst** · 10-18-2017, 11:32 AM

When I converted from r12 to r134, only the connection fittings were changed and the appropriate oil added. Mine works fine. not so good at low rpms. I don't think the pressure switches are hardly ever changed as the low and high pressures are close enough. As r12a is propane based, it should work with any oil. if you switched back to R12 then you need to go back to the appropriate oil.

**superj** · 10-19-2017, 06:56 AM

we just chose to run propane in our car, speaking of propane. works fine

**ELVA164** · 10-19-2017, 09:50 AM

Originally Posted by superj

we just chose to run propane in our car, speaking of propane. works fine

I don't think I could get over the knowledge that I filled the system with volatile, flammable gas...

**aaverhulst** · 10-19-2017, 10:21 AM

Originally Posted by ELVA164

I don't think I could get over the knowledge that I filled the system with volatile, flammable gas...

What do you put in your gas tank?

**Thecatmilton** · 10-19-2017, 10:50 AM

Originally Posted by ELVA164

I don't think I could get over the knowledge that I filled the system with volatile, flammable gas...

Think about it like a can of hairspray. Its about as dangerous as that in the extremely rare event that it does catch on fire. There would have to be an open flame and a massive leak for that to happen.

**superj** · 10-19-2017, 01:57 PM

propane is a liquid, its not a gas except for in a little bit of the system. just like gas in the fuel system, just a lot less. a small fuel line hole near a spark and you still get a flame thrower. mine will just go out a lot quicker since there is so little in the system.

I understand though, lots of people have that same thought so hardly anyone does it but since propane is sold as a refrigerant as r-290, I feel ok doing it

**ELVA164** · 10-19-2017, 06:03 PM

Originally Posted by aaverhulst

What do you put in your gas tank?

Not really sure what your argument is here. You'll have to expound a little on it.

Originally Posted by Thecatmilton

Think about it like a can of hairspray. Its about as dangerous as that in the extremely rare event that it does catch on fire. There would have to be an open flame and a massive leak for that to happen.

Still enough to freak me out. A/C systems leak a lot more than something like fuel, all else being equal, and I'd rather the gas was more inert.

Originally Posted by superj

propane is a liquid, its not a gas except for in a little bit of the system. just like gas in the fuel system, just a lot less. a small fuel line hole near a spark and you still get a flame thrower. mine will just go out a lot quicker since there is so little in the system.

I understand though, lots of people have that same thought so hardly anyone does it but since propane is sold as a refrigerant as r-290, I feel ok doing it

All true, but it's a gas when it leaves the system (which is the only time it matters in my hypothetical). It's not a huge risk, but like I mentioned above there isn't enough of a benefit for it to seem worthwhile to me...especially since I already spent all that time and money getting the R134a working so well

The fuel fire risk is why I pay attention to all those lines and fittings, and why I replaced all the soft hose right away.

**superj** · 10-20-2017, 06:41 PM

Ok. I understand.

**Clark Morris** · 10-21-2017, 10:13 PM

Ok Gentlemen,

I put in a new parallel flow condenser today, with a new Drier.... and I added around 1 oz of PAG oil to make up for the change out of the two items...

I also installed 2 cans of Duracool..... and then ran the system..... NO GO. It looks like my Compressor is kaput. Was getting no cooling at all...

SO now... maybe you guys can recommend a good compressor for me to obtain?.... I still intend to use R-12A " DuraCool" ......

Thanks for the advice ...
Clark

**Jeffnhiscars** · 10-22-2017, 12:16 PM

Why do you say the compressor is kaput...was it turning and wouldnt build pressure, is the clutch gone (was it getting power), or your pressure switches good etc etc

**82eye** · 10-24-2017, 12:24 PM

wondering about this duracool stuff myself. gonna attempt a system refresh next spring while my engine is still out of the car. i see parallel flow condensers and replacement compressors are still available. later cars were supposed to have come equipped with barrier hoses which should negate any issues with refrigerant leaking through the body of the hose. does anyone know when the hose change occurred ?

**Clark Morris** · 10-24-2017, 10:04 PM

Originally Posted by Jeffnhiscars

Why do you say the compressor is kaput...was it turning and wouldnt build pressure, is the clutch gone (was it getting power), or your pressure switches good etc etc

My Dad was running the gages.... said that the pressure was just about the same on both low and high side.... The clutch was working... but on all the time... not cycling like the instructions with the Duracool said it should.....

I did note that when we first were charging the system with Duracool... and then ran the engine... we heard a somewhat high pitched squeal for a few seconds... sounded kind of like a belt slipping.... We did look at the sight glass.... and could see coolant flowing... but the temperature inside the car never did cool....at all.

So .. Dad said he figured the compressor was now done. He said the pressure he did see was just the pressure supplied by the coolant can.

SO.... are there any particular brands or types of compressors that I should be looking at? I don't want to replace the compressor with the same old bad stuff from the old days..... would like to find something of a newer better design if that exists.

Clark

**demetk** · 10-24-2017, 10:36 PM

I use sanden "type" 508 compressors available on ebay for $120 shipped on all my m30's with some custom brackets,

I am not sure if my brackets will work with the M20 a/c bracket though.

My freon of choice is R152a. You can get R152a in these

Final pressures on my e28,

Final vent temp with the compressor engaged full time,

Total cost for a full charge = $10 bucks (2.5 10 oz. cans).

**E30Garage** · 10-25-2017, 12:14 AM

Interesting choice of freon, here's some product specific data that I found, handle with care.
http://www.falconsafety.com/wp-conte...-April2015.pdf

**Clark Morris** · 09-29-2018, 09:41 PM

Hey Guys,

I wanted to close out this thread with good news. I finally got the AC going properly.... A quick rehash......... A new compressor, new parallel flow condenser, new drier, and A/C hoses were rebuilt to handle R134a. All this did not get the system to a "decent" low temperature for use in Florida humid summer..... WHAT finally did it was that the heater control valve was replaced.... I suspected that the unit was not completely closing ... so I had the shop replace the old one. They found that the solenoid was not completely closing off the flow of engine coolant when the temp knob was fully counter clockwise..... So now ... with the new unit installed I an no longer fighting the heater core when the A/C is on. Am able to get the system down to 53 degrees when OAT is in the 80s.... and today at 94 degrees ... was able to live with 70 degrees in the cockpit......

After all these years! YEAHHHHHHHH!

Clark Out.