E30 Zone

I remember seeing this somewhere but searching doesn't seem to help much. I finally managed to source all parts required to retrofit the OEM AC unit on my 1989 M40 318i E30. I left all parts to an installer but there is one thing that I want some clarifications.

How does the idle increase when the AC is engaged? I thought it was supposed to be some sensor wired to the ECU? The installer tells me that the current wiring going to the ECU doesn't have such thing.

He told me that they will just raise the idle a bit (regardless if AC is on or off). Is this the correct approach?

Thanks!

Have a look in the Wiki for the ECU pinout......you will see there is a pin for the air-con idle.
You need to run +12 volts to it which you can take from the aircon clutch....or from the air con ON/OFF switch is easier... so when the air con is engaged the ECU signals an upping of the idle rate.

I would look up the exact pin number for you but I know Brianmooooore will beat me too it in any case......he has already posted about this issue before.


Edit: I think it is pin 40 on motronic 1.1 and pin 41 on motronic 1.3 but lets see what other people have to say.

Billwill wrote:Have a look in the Wiki for the ECU pinout......you will see there is a pin for the air-con idle.
You need to run +12 volts to it which you can take from the aircon clutch....or from the air con ON/OFF switch is easier... so when the air con is engaged the ECU signals an upping of the idle rate.

I would look up the exact pin number for you but I know Brianmooooore will beat me too it in any case......he has already posted about this issue before.


Edit: I think it is pin 40 on motronic 1.1 and pin 41 for motronic 1.3 but lets see what other people have to say.

I had an issue whereby the wires going to the AC clutch broke off so that when I had the air con switch ON the engine would idle too high due to there being no extra drag on the engine...this at least alerted me to the fact that something was wrong with the air con clutch!

NICE!

Pin 40. I have the Motronic 1.1 from what I understand (and remember), serial ending in 157. So it's just as simple as giving 12v to that pin. Only thing I have to dismantle that chunky plug?

There should be a small socket hanging off the engine loom near the ECU. The wire is purple/grey, and needs to be connected to the black/purple wire (from pin2 of the aircon switch), so that the idle speed is increased when the aircon switch is on.
There's also a black/grey wire that needs 12 volts from the connection to the aircon compressor, so that the ECU also knows when the aircon is actually working.
If you're using OE looms, it should be just plug and play.

Car was bought new back in 1989 so I'm sure that the wiring loom has never been tampered. Is there a possibility the socket near the ECU not to be there? Car was bought with no power windows, aircon, power steering or radio if it matters.

The branch to the plug is only about 3" - 4" away from the big ECU plug, and should be mounted in a small metal bracket attached to the LH ECU fixing screws, although this bracket has often gone missing after twenty years.

Perfect, will check tomorrow and post results!

Many many thanks

SPOT ON!

We found the plug taped to the main wiring loom, hooked it up and it works perfectly.