Engine stalls when Ac is turned on

[selespeed]

I have had the e36m42 swapped into my e30. but the engine tends to stall when air conditioning is turned on - rpm too low. I found out from diagnostics that the DME still shows Ac off. anyone here can tell me how to properly connect the wire so that DME knows when ac is turned on.

thanks.

selespeed

[DesktopDave]

Looks like you need some sort of a signal on DME pin 86, from the A/C controller? Given that you have an E36 motor in an E30, the body chassis might have a different wire. Did you swap the entire E36 harness?
http://www.m42club.com/forum/index.php?topic=14475.0

[selespeed]

Looks like you need some sort of a signal on DME pin 86, from the A/C controller? Given that you have an E36 motor in an E30, the body chassis might have a different wire. Did you swap the entire E36 harness?
http://www.m42club.com/forum/index.php?topic=14475.0

Yes. I have the entire E36 harness and ecu. But the wires are then soldered into e30. Do you have the pin connection diagram from E36 to E30?

[selespeed]

Looks like you need some sort of a signal on DME pin 86, from the A/C controller? Given that you have an E36 motor in an E30, the body chassis might have a different wire. Did you swap the entire E36 harness?
http://www.m42club.com/forum/index.php?topic=14475.0

is it pin 5? I have this wiring diagram. is it accurate?

[DesktopDave]

I found a reference in the E30 ETM. It shows no connection in the C101, but there is an A/C signal wire (black/violet) from the A/C switch to Connector 136/pin 2. The output wire (violet/gray) from C136/2 goes to the DME pin 86.

C136 is a small four-pin connector above the glove box, I believe.

[selespeed]

I found a reference in the E30 ETM. It shows no connection in the C101, but there is an A/C signal wire (black/violet) from the A/C switch to Connector 136/pin 2. The output wire (violet/gray) from C136/2 goes to the DME pin 86.

C136 is a small four-pin connector above the glove box, I believe.

I think we're going well too advanced into direct dme pin connections. What I meant Is the round socket where the two sets of wires meet. That's what my diagram says. Is it pin 4 or pin 5？

[selespeed]

I found a reference in the E30 ETM. It shows no connection in the C101, but there is an A/C signal wire (black/violet) from the A/C switch to Connector 136/pin 2. The output wire (violet/gray) from C136/2 goes to the DME pin 86.

C136 is a small four-pin connector above the glove box, I believe.

this plug contains wires of e36 side to plug into e30 socket

[DesktopDave]

Yep, I know you're talking about the main connector at the firewall. That big round barrel connector is called C101. It's important for most of the engine to chassis connections. There are a few other wires you need to connect depending on early or late production E30. Check the glove box for that little C136 connector.

The more I dig into this, the more contradictory info I get. Seems that there were annual changes in the E36 electronics. There are also two different HVAC systems in the E36 (IHKA and IHKR). Given that there were two different motors too - M42 and M44, there are a lot of potential combinations. The '96 E36 ETM I'm looking at has MANY different connections between the HVAC controls and the DME, as well as the vehicle lighting, transmission computer, security system, etc.. I think you'd need the donor's option list to puzzle this out...if it's even possible to drive the E36 DME with the E30's simpler HVAC electronics. Many of the E36 connections also use a digital signal to communicate, not an analog voltage like the older cars.

I'd be strongly in favor of using the E30 DME & motor harness with the E36 motor. That might be the easiest way to solve this problem.

[selespeed]

Yep, I know you're talking about the main connector at the firewall. That big round barrel connector is called C101. It's important for most of the engine to chassis connections. There are a few other wires you need to connect depending on early or late production E30. Check the glove box for that little C136 connector.

The more I dig into this, the more contradictory info I get. Seems that there were annual changes in the E36 electronics. There are also two different HVAC systems in the E36 (IHKA and IHKR). Given that there were two different motors too - M42 and M44, there are a lot of potential combinations. The '96 E36 ETM I'm looking at has MANY different connections between the HVAC controls and the DME, as well as the vehicle lighting, transmission computer, security system, etc.. I think you'd need the donor's option list to puzzle this out...if it's even possible to drive the E36 DME with the E30's simpler HVAC electronics. Many of the E36 connections also use a digital signal to communicate, not an analog voltage like the older cars.

I'd be strongly in favor of using the E30 DME & motor harness with the E36 motor. That might be the easiest way to solve this problem.

I have the e36 DME plugged in. and the hardness also comes from e36. but can you tell me from the diagram which wire(s) to solder to connect?

[DesktopDave]

The A/C signal wire does not come through the C101 connector on the E30. If you want to splice it into the C101, I'd think you could run a jumper wire from the A/C signal wire (black/violet) at the A/C switch, or from C136/pin 2 (black/violet in-violet/gray out) to whatever C101 pin the E36 harness is expecting to see an A/C signal. I'm not sure which pin that is, maybe 4 or 5? I think it ends up at Pin 48 on the DME.

[selespeed]

The A/C signal wire does not come through the C101 connector on the E30. If you want to splice it into the C101, I'd think you could run a jumper wire from the A/C signal wire (black/violet) at the A/C switch, or from C136/pin 2 (black/violet in-violet/gray out) to whatever C101 pin the E36 harness is expecting to see an A/C signal. I'm not sure which pin that is, maybe 4 or 5? I think it ends up at Pin 48 on the DME.

Dave,

my original DME is from 316i M40B16 of European specification. this has A/C signal properly working. therefore, I believe it is already properly wired. when A/C is turned on, it sends a signal to DME that it is on and so the engine revv is higher. I am not sure why you said the A/C signal doesn't come through the C101 connector? if it doesn't where does it come from?

thanks

teo

[selespeed]

The A/C signal wire does not come through the C101 connector on the E30. If you want to splice it into the C101, I'd think you could run a jumper wire from the A/C signal wire (black/violet) at the A/C switch, or from C136/pin 2 (black/violet in-violet/gray out) to whatever C101 pin the E36 harness is expecting to see an A/C signal. I'm not sure which pin that is, maybe 4 or 5? I think it ends up at Pin 48 on the DME.

I got the A/C sorted but it is now giving me a other problems. the diagnostics always produces errors. even when the A/C switch is off, the DME still says both A/C and A/C compressor are ON. the mechanic did not want to tell me what he did. but I think he probably short wired directly the DME such that the A/C is permanently on. should I be worried? the errors always say pin 85 and pin 86

what do you think he has done and how to undo this?

also, why is there a separate switch for A/C pin 85 when there is already pin 86 for A/C compressor on? when you turn on A/C compressor, isn't the A/C inside the cabin also on? is it possible that even when A/C compressor is on A/C (pin 86) kan be off? how to do it in away that is like original e30?

thanks.

[DesktopDave]

Find the two electrical troubleshooting manuals (ETM) you need. They're downloadable from this page, and I think you can also get them from BMW with a small fee attached.

You'll need an ETM from the donor car engine (E36) and one for your chassis (E30). Spend some quality time with the block diagrams to understand how the A/C system functions. Those ETMs are a lifesaver - they specify what the wire colors are, where the connectors and grounds are, and how the system is designed to work. You'll save a fortune in service costs once you learn the logic behind those ETMs.

I wouldn't be worried if the car runs well. Don't fix something unless it's broken.

I'm not entirely sure what your mechanic has done; you should pull the DME connector shell off and take a look.

The A/C compressor is not on all the time. It has to send a signal to the DME when it's running as it cycles on and off. The compressor also can be powered on without the A/C button. IIRC the defrost setting will automatically power up the compressor in some BMWs, and in some models full throttle will automatically disable the compressor in the automatic transmission versions. The E30 HVAC system is far simpler than the E36 automatic IHKA versions; it may not be possible to have it wired to function exactly as the E36 does but a little research should point you in the right direction.