A/C Compressor E90 through CAN

[Btune]

Hey Guys im having some issues getting the AC Request from a BMW E90.

I got some info from the interwebs and so far this is what ive got.

CANID in dec 726

Any help would be appreciated.

 

[Adamw]

You would need a start position of 15 and a width of 1 to pick up the 252/253 change in your pic.  Also, make sure you have the receive filter at the top selected when you are in the "add parameters" selection screen.

[Btune]

Thanks for the response Adam.

No success yet.

Any difference if its LS First?

[Adamw]

10 hours ago, Btune said:

Any difference if its LS First?

No, ecu setup would be the same and LS/MS first would work the same since we are only looking at a single bit.  

Most likely the CAN info you have is not actually the AC request - it may just be something related to AC such as the blower is on or a clutch status etc. 

You will really need a sniffer to confirm.  

[Vaughan]

I've been sniffing my E82 and looking into making a CAN mode, can check what info I have for that when I get back to work.

[Btune]

I will be getting a sniffer and check whats going on over there.

Hey Vaughan, that would be of great help.

[Vaughan]

Just had a look at my documentation and I don't have ac request mentioned anywhere in it yet. Interestingly though I haven't seen ID 0x2D6 (726 in decimal) in the CAN from my vehicle or in any of the documentation I have read, are you able to share your source?

[Btune]

https://www.loopybunny.co.uk/CarPC/k_can.html

[Vaughan]

31 minutes ago, Btune said:

https://www.loopybunny.co.uk/CarPC/k_can.html

I had seen that one, one thing to be aware of is that hasn't necessarily been scoped from the ECU pins, good chance it was scoped at the OBD2 plug and so will see different messages to the ECU.

One thing you could do while you wait for your sniffer is feed full bytes or even pairs of bytes into CAN Analogs, this would mean if the CAN Analogs show anything other than 0 you have received a message on that ID and you can then also see what the values are with AC on and off to narrow it down if you are receiving messages on that CAN Id.

As a side note I'm not seeing anything in the ECU pinout that says it controls the AC Clutch so I wouldn't be surprised if it doesn't get that particular message but rather gets an AC Clutch on message from the body computer.