Making Air Con work in a '96 855 with running a M4.4 ECU - Help please

[kmb]

Hello all,

I have a M4.4 ECU in my '96 855 which was mapped by Oblark and certainly makes a difference to performance, however the only downswide appears to be that the Air Con no longer works when running M4.4 on an 850 :(

Now the weather is warming up I would really like my nice cold Air Con back, but not at the price of putting my old unmapped ECU back in.

This leaves two options as far as I have found through scouring the internet:

- Reprogramming of the M4.4 removing some software file which will enable the Air Con to work again.
- Some hardware modification which will enable the Air Con to work again.

As the first option will involve sending the ECU away again and Oblark knowing what needs to change plus reprogramming for me, I prefer the second if it is relatively easy - Anyone know what the hardware modification is and how to do it?

Thanks in advance :)

[c70geoff]

Really air con don't work after remap
That sucks

[jamesy12345]

I've got no personal experience of this but see below...

http://m44.wikia.com/wiki/M4.4_A/C_Converison

Hardware modification described as follows...

HARDWARE MOD Edit
Inside the M4.4 ECU:

1. Cut leads between ECU connector and circuit board for pins B6 (voltage after pressostat switch for compressor status indicator, M4.3 only), B25 (voltage from AC relay for M4.3, AC request for M4.4) and B40 (ground to activate AC relay).

2. Solder a wire between the connector side of B40 and A13 (power ground,do NOT cut this lead, just solder to it) to enable the AC relay to be activated by the ECC module. Leave the board side of B40 open, and press it down and out of the way. This basically hard-wires the ground side of the AC relay. Positive voltage is applied to the relay by the ECC module when the AC is turned on, engaging the relay, which in turn engages the AC compressor (assuming the pressostat hasn't opened, which cuts the compressor off to keep system pressure in check).

3. Solder a resistor of a few kohms or so (I used 4.7k) between the connector side of B6 (which gets power from the compressor clutch) and the board side of B25 (ac request). This causes AC request to go high when the compressor is on (actual power to the clutch), thus causing M4.4 to do idle correction when the compressor clutch is actually engaged. Leave the board side of B6 unconnected (it is not used on M4.4). Also leave the connector side of B25 unconnected.

Accessing some of these leads will require bending the other leads out of the way, as they are in three rows -- B40 and A13, on the bottom row, are most difficult to get at, but bending the other leads to the side (to make a hole in) allows access. They're flexible, but do be gentle. You will need a pair of snips with a fine tip, as well as a soldering iron with a fine tip.

Only issue is ECU has no control over A/C, so on hard accel it will stay on, but honestly i dont see that as a problem, because that was annoying anyway, plus when the AC is on the radiator fan will always stay on.

[kmb]

Thanks Jamesy, good info - Although sounds way to involved for me and I'm not at all keen on soldering and snipping wires around inside the ECU :(

Unless there is anyone near Sudbury Suffolk/Essex who could do it for beer tokens?

[jamesy12345]

Thanks Jamesy, good info - Although sounds way to involved for me and I'm not at all keen on soldering and snipping wires around inside the ECU :(

Unless there is anyone near Sudbury Suffolk/Essex who could do it for beer tokens?

I don't think I'd have the bottle to do it either with a mapped ECU...mind you neither of my cars have AC - I just open the window :)

[kmb]

We'll see what willing volunteers step forward or if Rob (Oblark) can help :)

[dant5r]

Try getting in contact with Avinitlarge on here.

If you read oblarks remapping thread he sent his ecu to him to have the ostrich fitted.

[kmb]

Thanks Dan - I've dropped both Oblark and Avinitlarge a PM.

[Avinitlarge]

Thanks Dan - I've dropped both Oblark and Avinitlarge a PM.

Well, hmmm. It's easy to sort out. There are 2 ways of doing it. Hardware mod inside the ECU or a soft mod.
Hardware mod requires cutting, soldering and adding a resistor or 2.
Soft mod is easy but the ecu file needs to be dumped, edited then rewritten. If a 607 or 608 file has been used then it's pretty straight forward, if not then the whole file needs altering

[kmb]

Thanks for the prompt response, the software mod sounds best but not sure how Oblark has performed the ECU rewrite - Probably need some input from him on whether he knows how to wipe, edit and reload.

Would you prepared to perform the hardware ECU change? Would you PM me a price?

[MoleT-5R]

Really air con don't work after remap
That sucks

Thats it because he has upgraded his management system to a mapped 4.4 ecu from 4.3 ecu which the car was originally running, if a mapped 4.3 ecu had have been fitted the air-con would still work, but kmb has gone for a 4.4 as re-mapping this can be done relatively easily and there is more scope for data logging and expansion.

[Avinitlarge]

I've altered Oblarks XDF so he can do the soft mod for you now. Im just too busy at the mo.

[kmb]

Huge thank you to both Avinitlarge and Oblark, much appreciated in advance for your help - It's not a critical thing, but certainly a 'nice to have' if we actually get a UK summer.