Is AC Evaporator replacement necessary in R12->R134a conversion?

[bbohica]

I'm repairing an AC system from a blown compressor and attempted a 134a conversion at the same time. The procedure to replace the evaporator is ridiculous. Have you seen this [ame="http://www.youtube.com/watch?v=m-Q-kT2HS3g"]video[/ame]? There are several o-rings and the evaporator that I'm not able to replace because I'm not willing to take my dash out. I've replaced everything else though.

I just read that its the PAG oil that breaks down the o-rings, but ester oil is safer. I already filled my new dryer with PAG. If I use R134a, will the old evaporator work or is there something really different about it? If I choose to stay with R12, i'll switch to ester oil, in fact, I'll probably switch anyway because of the old o-rings in the system.

[slocar]

I believe the old evaporator can stay.

BMW sells a R12>r134 retrofit kit. Part number: 82 31 9 067 403 ... it's about 180 dollars. It includes the following:

01 29 0 017 969 Stick-on label EBA-AUFKL. GELB 1
01 29 9 788 367 Installation instructions R12 AUF R134A 1
64 11 8 363 259 Filling valve adapter 1
64 11 8 363 260 Filling valve adapter 1
64 50 8 363 258 Label "retrofit" 1
64 50 8 390 602 Gasket ring D=11.1MM 3
64 53 8 372 977 Drying container 1
64 53 8 390 582 Safety pressure switch

I would say BMW knows what is needed to convert it a lot better than some guy from Taiwan moving really fast in a youtube video.

[csmc1013]

There are a few things that are/is needed, but its been eons since I tried a conversion.

Evaporator may work (metal is metal), but there is a needle like (on most cars) device, aka expansion valve/tube/orifice that regulates the flow of freon into the evaporator. R12 and 134 have diff weights, so, may or may not work better with diff freon.

Oils - PAG is supposed to settle out of the system when ester is introduced, or something like that (google to make sure which oils do). It is supposed to collect in the dryer. They say to flush as much of the system you can and I guess whatever is in the compressor, since you cant really flush that, will drop in the dryer.

I say drain all you can and go for it. Whats going to happen, you have to do the seals like originally thought? Just remember, refilling anything past what the .oz is is a no no. If it works at that point, it works. Of course the preferable route is to try to replace what is said by a well known source.

[bbohica]

Well, it's finally cold. Swapped the PAG oil for Ester, and went for the 134a. The thing was pissin me off, high side = low side on pressure, seemed like compressor was dead. I finally started checking fuses and found a blown fuse, (7.5A #41 I think?) replaced it, and numbers started looking normal. Filled it with what was left of the 134a, I think it needs about 6-8 oz more, but it's cold so I'm happy it all works just before it gets hot as hell here in TX.

Now the tough question...

which one to sell... '01 330i, or '92 325i w/ M3 suspension... wife won't let me keep both .

[slocar]

I'd want the 330 over any non-m e36, but that's just me. E46s are much more refined and a lot nicer/modern looking than a e36.

[flyfishvt]

I'd want the 330 over any non-m e36, but that's just me. E46s are much more refined and a lot nicer/modern looking than a e36.

Yup I agree. BMW did manage to learn some lessons from mistakes that were made on the e36 and made some changes on the e46 when it comes to engineering. They didn't fix them all but they fixed a bunch.

I always liked the more refined lines of the e46.

[bbohica]

Oh, btw, I only started looking onto charging the system myself because my repair shop quoted me $300 to evacuate and fill with r12. I rented the pump and gauges for free at auto zone and spent under $40 total for oil and r134a.

[flyfishvt]

Oh, btw, I only started looking onto charging the system myself because my repair shop quoted me $300 to evacuate and fill with r12. I rented the pump and gauges for free at auto zone and spent under $40 total for oil and r134a.

I had to replace my condensor coil and some lines last summer. I never pumped the system down and they wanted $125-150 at all the shops around here. Im not doing a conversion because its already a 134 system.

My question is how do I know if it has enough oil? If auto zone loans the pump I would love to pump it all down the right way but I'm not sure if i need to add oil or if you can add too much. I have my own manifold set so all I need is the pump.

[csmc1013]

If you break the system you HAVE to pump it down. It will not work with ANAY (maybe it will but not good at all) air or moisture at all. You have to pull down to get the air out and leave running for no less than 15 minutes to burn (odd way they put it) the moisture out. Basically the vacuum supposedly makes the moisture bubble, aka boil and comes out somehow. I have not got a grips on how that works as I am not a chemist, but thats what they say.

[flyfishvt]

The boiling point has to do with surface tension and air pressure that is it in very simple terms. Not all liquids boil at 212F like water. Liquid nitrogen boils at something like -200F (don't quote me exactly on that) but you get the idea. So it makes perfect sense that you would describe it that way. You can make wate boil at room temp if you create a vacuum. Water boils at lower temps in the mountains. I understand all that. Create a vacuum in the system and the water boils out.

My question is still about how to tell if I have enough oil. Is there a way to evactuate all the oil so I can just replace it?

I assume I'll have to get another dryer too. My A/C does work and it works well but then I don't deal with any temps over 90F more than a dozen days a year.

But the whole thing has bothered me that I didn't do it the right way.

[bbohica]

The guidelines I read were, put 4 oz of PAG in the dryer when you replace it. I read the actual oil volume is supposed to be more like 8 or 10 oz, so I'm not sure what to think about that. Once you have the the system pressurized, I don't even know how to put more oil in it unless you can fill the freon hose full of oil , then let the freon push it in?

I obviously used Ester oil instead of PAG as I mentioned above though. I used about 4 oz, but I'm thinking I probably needed a bit more than that.

[flyfishvt]

they make freon recharge canisters that add a small amount of oil at the same time.

EDIT: I just called my local Auto Zone and they dont have the pump to pump down the system. Actually I think the guy I talked to didn't know what I was talking about and just looked at a list of tools they have and couldn't find anything close.

[Toby B]

eh, the oil question really has no answer, as I understand it. There are tables of
how much each component retains 'on average' and you just add back that much.
I've tried to find the same answer, and 3 or 4 OEM manuals say the same thing-
'replace what you've removed'.

OR you completely blow out the system with a special solvent and start from scratch.
But that's reputedly a rather expensive, big deal. Only Mitsu dealt with that,
and in terms of MD part numbers.

I get the sense that as long as you're in the ballpark with oil, the level of
refrigerant is a lot more important.

But I know less than the average internet moron...

t

[paniolo]

The shops that do recharges pull all the coolant out, their machines separate the coolant (r134) and the oil. Then they do a full recharge based on the total grams the system is speced for of r134 and add the same amount of oil that they pulled out.

Flyfish, so you replaced your condenser but no other components? Was your system unpressurized (empty) before that replacement? Assuming so it had been exposed to air for awhile. Did you replace your dryer? This pdf lists avg amounts of oil in various components at the bottom of page 2. An average condenser has 1oz and an average dryer has 1oz. So you may want to add back 2 oz of PAG 46 oil.

Pulling a vacuum is, exactly as you figured, to allow all water vapor to boil off. As the air pressure drops the boiling point of water does too. So pulling a good vacuum and holding it for 15-30min will purge any water vapor from the atmosphere out of your a/c lines. I think the water vapor is an issue as it forms rust at the expansion valve and compressor? Not real sure, just know everybody says you need to get rid of it! Which is also the purpose of the dryer. It just contains desiccant to absorb out any moisture that then gets into the system.

My autozone does show a vacuum pump in their tool rental ... but they couldn't find it. Other stores may have them for loan too. You can buy a venturi style pump from Harbor Frt for about $40, but need a good compressor to run it. If you want to pull a vacuum now you would need to evacuate the R134 in there first. Which sends you right back to the shops you didn't want to use in the first place.

[flyfishvt]

The shops that do recharges pull all the coolant out, their machines separate the coolant (r134) and the oil. Then they do a full recharge based on the total grams the system is speced for of r134 and add the same amount of oil that they pulled out.

Flyfish, so you replaced your condenser but no other components? Was your system unpressurized (empty) before that replacement? Assuming so it had been exposed to air for awhile. Did you replace your dryer? This pdf lists avg amounts of oil in various components at the bottom of page 2. An average condenser has 1oz and an average dryer has 1oz. So you may want to add back 2 oz of PAG 46 oil.

Pulling a vacuum is, exactly as you figured, to allow all water vapor to boil off. As the air pressure drops the boiling point of water does too. So pulling a good vacuum and holding it for 15-30min will purge any water vapor from the atmosphere out of your a/c lines. I think the water vapor is an issue as it forms rust at the expansion valve and compressor? Not real sure, just know everybody says you need to get rid of it! Which is also the purpose of the dryer. It just contains desiccant to absorb out any moisture that then gets into the system.

My autozone does show a vacuum pump in their tool rental ... but they couldn't find it. Other stores may have them for loan too. You can buy a venturi style pump from Harbor Frt for about $40, but need a good compressor to run it. If you want to pull a vacuum now you would need to evacuate the R134 in there first. Which sends you right back to the shops you didn't want to use in the first place.

HOLY CRAP!!! that was a year ago LOL. I dont even have that car anymore. Sold it for $3000 and bought this vert for $2000. Actually I only paid $1850 but I gave my buddy $100 for loaning me the money for a week.