S50 swap with AC

[RoadHazard]

What kind of coolant do you guys use? Is converting to R134 a good idea?

Do you keep the S50 compressor? If so how do you modify the hose connectors to match the S50 type?

Thanks.

[ian332isport]

What kind of coolant do you guys use? Is converting to R134 a good idea?

Do you keep the S50 compressor? If so how do you modify the hose connectors to match the S50 type?

Thanks.

You'll need to retain the S50 compressor, and this forces the change to r134a.

I made some hose adapters to convert from the S50 style block connectors to a regular threaded fitting like the E30 hoses. It's just a set of E36 hose ends cut down with some threaded fittings silver soldered on the end of the pipe. I then had them plated to stop corrosion.

You'll also need to get some of the pipes modified/custom made, as the E30 hoses are the wrong shape/length to connect to the S50 compressor.

Cheers,

Ian.

[RoadHazard]

If I convert to R134a, what do I need to change in the current system? I know I need a bunch of new seals and a new dryer. Anything else? Is this something I can do myself?

[ian332isport]

If I convert to R134a, what do I need to change in the current system? I know I need a bunch of new seals and a new dryer. Anything else? Is this something I can do myself?

New seals and a new dryer is about it. You're best off getting the BMW retrofit kit, as this comes with the dryer and the correct pressure switch for r134a.

I did all the work on my AC installation, apart from the silver soldering and the fabrication of the custom hoses. Certainly DIY'able if you're reasonably competent.

Ian.

[crossie]

@ian332isport

Do you have any photos of your conversion online?

[ian332isport]

@ian332isport

Do you have any photos of your conversion online?

Engine conversion, or Aircon ?

[crossie]

Both Ian
Had a quick search but didn't find any just photo diary of your suspension update which was very good

[turk]

if pix are available id like to see this too.

[RoadHazard]

Guys I'm still in the middle of AC conversion. Actually the AC system is being retrofitted. The stock one on my car is "different" I just don't want it so I'm converting to a standard E30 HVAC unit. And today I have a wiring question.

I added a compressor control relay the same way as in the E36 since I can't locate the one on my HVAC unit. And I hook 3 wires to the S50 DME:
- pin 48 from the compressor relay (compressor control)
- pin 64 from C136 pin 2 (AC on signal)
- pin 65 from C136 pin 1 (Pressure switch monitor signal)

This results in a strange behavior. The compressor is turned on when the AC switch is OFF, and turned off when the AC is on. The idle rpm is also raised when AC is off. I tried disconnecting pin 64 and it still acted the same way! It looks like the DME is ignoring pin 64.

Disconnecting pin 65 is the same as having the pressure switch open, i.e. the compressor is off. So this pin works correctly. (Although I can only test this when the AC is off. )


Hope you all can follow what I'm trying to say. Any ideas?


edit:
I double-checked. Voltage across C136 pin 1 is normal. Off when AC off. On when AC on.

[DanThe]

Ian is the man for this as he used the E36 ECU controls, I do know that the idle increase is triggered by an earth feed to the ECU though

[ian332isport]

This diagram shows what needs to be done. I don't think the idle speed increase is triggered by an earth feed though. It's the one connection that isn't

[ian332isport]

Oh, and don't get too hung up on the X20 pin numbers or fuse numbers etc. That's just how it is on my car.

The two small black relays are similar to the half sized relays already on the S50 engine harness, but one is different internally. I got them from Vehicle wiring products. Any relay with the same configuration will work.

Ian.

[DanThe]

Oh well, I was only completely wrong

Must be the M50 that uses earth on the idle increase

[turk]

If im using the s54 compressor with everything else e30 do i need to do this too?

[RoadHazard]

Thanks Ian. That's what I need!

Basically I've wired the logic on pin 65 backward right now. And it makes more sense to use bk/rd at 64 just like in your diagram rather than bk/vi like what I'm having.

I'm using the E30 aux fan wiring so that part will not be used.
For pin 64, I'll use a transistor instead of a relay simply just because I have one available right now. Don't think that pin will take a lot of current.


I'll try it out and let you know.

[ian332isport]

If im using the s54 compressor with everything else e30 do i need to do this too?

Only if you want the ECU to control the compressor. It will work fine wired as per the standard E30 wiring. Using the S54 compressor won't make a difference.

Ian.

[turk]

ah brilliant! What about the dryer bottle? is the e30 one compatable with the newer type gas?
Cheers
Adem

[RoadHazard]

Come to think about it. That makes me wonder why the DME would need to turn on the high speed fan? Is temperature control not enough?

[ian332isport]

I'm using the E30 aux fan wiring so that part will not be used.

I'm also using E30 aux fan wiring. I wired it like that to allow the ECU to engage the high speed fan independantly of the temp switch. If the ECU thinks the engine is too hot, it can engage the fan even if the temp switch was to fail. It's certainly not necessary, but nice to have

For pin 64, I'll use a transistor instead of a relay simply just because I have one available right now. Don't think that pin will take a lot of current.

A transistor should work fine, but is one really needed ? I'm just using the signal from the E30 aircon relay (on the heater box). It's 12v when you switch the A/C on, so just a direct connection.

Cheers,

Ian.

[ian332isport]

ah brilliant! What about the dryer bottle? is the e30 one compatable with the newer type gas?
Cheers
Adem

If you get the correct one from BMW it will be fine with r134a gas. I think that's all they would supply now anyway.

Ian.

[RoadHazard]

For pin 64, I'll use a transistor instead of a relay simply just because I have one available right now. Don't think that pin will take a lot of current.

A transistor should work fine, but is one really needed ? I'm just using the signal from the E30 aircon relay (on the heater box). It's 12v when you switch the A/C on, so just a direct connection.

Cheers,

Ian.

I meant to say pin 65.

[ian332isport]

I meant to say pin 65.

DOH!

Transistor should do nicely for that one. very little current flowing on that circuit.

Ian.

[RoadHazard]

Ok Cool. I'm off to the car now. Thanks again. And Happy New Year everyone.

[RoadHazard]

I got the AC circuit working correctly now. Thanks again everyone. Next I'll replace o-rings and connect all the pipes.