A/C Question on Freon

[BingM3]

Ok, the E30's are R-12's right?

So once I get my AC lines done to bolt into the E36M3 motor, compressor, do I use R-12 still or convert to R134 and use 134 freon?

Maybe a noobie question but thanks for your input.

Bing

[Van Westervelt]

134

[Blake325is]

Yes, 134a will be much cheaper, but check for compressor compatibility. Expansion valve should also be r134a compatible, and you'll need a new drier. You'll need a conversion kit that includes o-rings and fittings for refilling r134a.

[kroberts]

I'm just finishing this part of my project, here's what I've found. The E36 compressor is already made for r134 so you're all set there. You need to buy a new dryer and expansion valve. You should be able to get both for about $60 (total).

Getting to the expansion valve is something of a bitch. It is next to the glovebox. The cover over it has one screw tucked way up in the corner between the firewall and the AC box. It will probably be a lot easier if you pull the passenger's seat out and kinda lay in there with it all. There is a foam seal around the valve that will probably be dry-rotted, and some tacky tape insulation on the connectors. You'll have to improvise a little during re-assembly. Be careful when you connect the tubing to the valve, especially the bottom connections. Make sure you support the valve very well because the tubing has very thin walls and they like to bend when you torque the tubes to the valve.

You need to buy a new o-ring kit and replace all the old black ones with new green ones.

HTH,

kr

[bwh13]

You shouldn't have to replace the expansion valve when swithching to 134a. The characteristics of both freons is similar and the R12 valve will work just fine. Overcharging the system by 3-6 ounces will offset the difference in heat absorbtion capacities between the 2 freons...make sure you use 134a oil in the system.

[hoveringuy]

Duracool!

134 just doesn't work in e-30's (condensor is too small). I've been running Duracool in Washington DC and have been happy with it. Unless I'm stuck in stop-and-go traffic I get excellent vent temps on hot days. It's compatible with mineral oil and the old compressors and is cheap.

Of course, if you can get R-12 you're best with that but I wouldn't bother with 134

Only my opininion.

Hoveringuy (finally on the way back from the sandbox!)

[oldcarskickass]

You still need to change all the o - rings with the green ones, and the expansion valve.

Thats because R134a is lighter than the R12 and usually when you refill (with 134) the machine recharges the system with the same weight as the R12.

So the pressure in the system with the R134 will be bigger causing it to lose from there (ask me i know).

If you want to use your retrofited system daily you MUST replace the number 8 (part number 64538391051)from that link 64538391051. You can use the line you have on now, but in my car i blew up two original OEM lines (the second one came from a part car)that were supposed to be used only with r12.


Be sure to use the oil made for the specific compressor (E30 had Seiko seiki, Bosch and Behr, and all of them need different viscosity oils for 134, dunno for the e36's, but that wont be such a trouble to check).

Please excuse my grammar mistakes, glad to help.

[bwh13]

The condensor can't be any smaller than the one on my old Civic and with the extra few ounces of 134 it worked just fine, have the shop do a manual fill, not a machine one...I forgot about changing the o-rings to ones compatible with 134, different type of rubber.

[Mr.SWISS]

I filled mine up and the high pressure switch kicked the compressor off during the second can fill. Total ounces was 34.

[bwh13]

You had too much freon and it created a too high of head pressure, so the switch did it's job to prevent a blow out...

[Mr.SWISS]

You had too much freon and it created a too high of head pressure, so the switch did it's job to prevent a blow out...

But the system capacity of R12 is 2.2lbs, isn't 134a more dense? I only put 34 ounces in it of 134a...

[netcsk]

you have to bypass the high pressure switch due to your system needing far higher pressure with 134a. Should be directions around somewhere.

[bwh13]

Unless the higher pressures with the 134a is something unique to BMW, by-passing the high pressure switch shouldn't be necessary. Many cars have been switched to 134 without having to bypass the high pressure switch....

I don't know about the difference in density between 12 and 134, all I know is the shop that filled my car said by adding a little more to the system would help it cool down more. 134 does not have the same heat transfer capacity as 12 so the systms usually have larger condensors to allow more heat to be removed in the same amount of time...