The Detailed E30 R-134a Conversion Thread/DIY

[nick.cbr]

I don't know why anyone struggles with converting to R134a, just run R12a.

This. I made zero changes to my hardware. Verified system held vacuum and charged with FrostyCool R12a that I got on eBay (I think it's a way better deal to buy direct from their website even though shipping is ~$19 though so I'd probably avoid the eBay seller). I was getting 41*F at the center vents on idle (fan on 2, recirc ON) and a consistent 33*F at cruise (at one point I saw 32.x*F). Ambient temp was ~70*F and very high humidity; waiting for the heat to come back to do some more testing but I expect some pretty good performance out of the system.

Per the FrostyCool website, I used 11oz of their R12a refrigerant to charge the E30 system that calls for 2.1lbs (+/- .05) of R12. For equipment, I used some manifold gauges, R134a conversion fittings and a two-stage vacuum pump - all off Amazon. I left my existing dual pressure switch setup in place as well as the stock expansion valve. I'm still playing with things so I'll report back with more concrete data on pressures and things like that. I thought I may have overcharged the system so I vented some refrigerant out and now I believe it's under-charged again as my idle vent temps went up to 52*F and cruise vent is 37*F. All of this is on factory R12 parts namely the condenser (fin/tube not parallel flow).

I had another E30 325iX converted to R134a about 10 years ago and that car performed admirably; however, I really think sticking with the R12 system (tube and fin condenser), replacing the dryer and all the o-rings is the correct solution for these cars. Based on my research, I'm just not concerned about running a hydrocarbon-based refrigerant either (a common argument against R12a). It is unfortunate that the EPA hasn't approved this as a replacement for R12 systems as it is better for the environment than even R134a (which is no longer in favor anyway as everyone is switching to R1234yf or whatever it is).

[808ETA]

Since I had was replacing everything with new parts I decided to sent my A/C compressor out to be rebuild. It was working fine however I didn't want to have a weak link in the system and have to go in there again. Mike from Discount A/C was very informative and rebuilt it in 1 day. Shipping wasn't bad either as it fit in a USPS medium flat rate box. Total cost was $172 including shipping, insurance and pulley bearing replacement. They also have good prices on new and rebuilt A/C

http://www.discountautoac-compressor...or-C20804.aspx

[e30davie]

I don't have any oil cooler. I don't think any of the M20b23 had an engine oil cooler. Mine was originally auto, dunno if the manual one did.

[Tzantushka]

Thought some of you might be interested in the compressor that i put on my m20b23.

Nice!
You have the stock oil cooler I assume?

[e30davie]

Thought some of you might be interested in the compressor that i put on my m20b23. I couldn't find an oem r134a compressor in Australia for less than about $1600 aud....

So I used a Sanden SD5H09 gineric R134a compressor, that only cost me about $330 AUD brand new. You can get them with the V belt or the ribbed belt, obviously get the V belt one. probably even cheaper in the USA.

I made my own bracket as the oem compressor has a really long nose on it and the Sanden is significantly smaller than oem. In heinsight i should have made the bracket so the compressor sits slightly lower as it does make the CAS very hard to remove (i have an m20b25 CAS - megasquirt)

I then had to modify the hard lines - you can see where i TIG welded on a new fittings to the hard lines (after cutting off the rubber bit) - these were called "bulk head connectors" for AC lines. Then just got some hose and fittings and made new lines to suit - these from were a vintage AC shop - really quite cheap and easy to make - supplied with a crimping tool. excuse my welding - first tig project - but it doesn't leak!

The rest of the r134a conversion was same as specified, i did just re-use the r12 condensor. seems to work fine. New TX valve and dryer were pretty cheap and then I just put new R134a orings everywhere. got it gassed a month or two ago, and works quite good and the sanden is very quiet, hardly tell its on.

I have since put a bit of heat protection on that AC rubber line - but its not as close to the exhaust as it looks in the photo.

Apologies for the photos uploaded weird.

[808ETA]

Awesome! Were you able to use the dryer we discussed with the 2-switch set up?

Cory

Yes, It worked perfect. No need to cut or splice any wires. Thank you again Cory!

[808ETA]

Awesome!
Another success story helps convince others that this approach is a true & trusted solution.

For sure! This is about 20 degrees cooler than just changing the fittings and adding 134a like I did initially.

[cory58]

Got everything buttoned up and system recharged!! Thank you again for everyones tips and help!

Awesome! Were you able to use the dryer we discussed with the 2-switch set up?

Cory

[Tzantushka]

Got everything buttoned up and system recharged!! Thank you again for everyones tips and help!

Awesome!
Another success story helps convince others that this approach is a true & trusted solution.

[808ETA]

Got everything buttoned up and system recharged!! Thank you again for everyones tips and help!

[jeffnhiscars]

I get asked often enough about AC that I wanted to share this. It explains rather clearly why using a manifold gauge to figure out when you've pulled a proper vac is an exercise in futility. The difference between 500-1000-1500 microns is a hairs width on the dial.

[cory58]

Thank you Cory! My dryer says 64101 however the box has the same PN and it looks the same. I'm going for it!

Let us know how it goes. I bought the wrong dryer first. They both looked the same but the plug where one of the switches mounts could not be removed. I tore it up trying to get that plug out.

Cory

[808ETA]

Sorry - I meant Mahle/Behr, not Bosch. I think you have the right dryer for the 2-switch set up. Here are the part numbers I have.

On box - AD240000S
On dryer - 50986A

Cory

Thank you Cory! My dryer says 64101 however the box has the same PN and it looks the same. I'm going for it!

[cory58]

Thank you Cory!

The new one looks exactly like my old one but the PN on my old one is worn off. I bought the Mahle AD 240000S which shows up as PN 351200091 and 64531466051. If you could share your part number that would be awesome!

Sorry - I meant Mahle/Behr, not Bosch. I think you have the right dryer for the 2-switch set up. Here are the part numbers I have.

On box - AD240000S
On dryer - 50986A

Cory

[808ETA]

Yes - you can use your existing pressure switch set-up, but there are different dryers for 1 vs. 2 switches. I kept 2 switches when I upgraded my system, but had to reorder the correct dryer. I can find the Bosch part number if needed.

Cory

Thank you Cory!

The new one looks exactly like my old one but the PN on my old one is worn off. I bought the Mahle AD 240000S which shows up as PN 351200091 and 64531466051. If you could share your part number that would be awesome!