C1726 and C1964 DTC's for air suspension

[Drewstang]

I tried searching and couldn't find anything on the forums, but my new to me 03 MM has developed an air suspension issue. The rear is lower than normal, no obvious signs of an air leak. The car has sat overnight and the rear has not changed positions. I had the car on jack stands for about a week with the rear end unsupported. After placing back on the ground and turning the air ride switch back to the on position, the compressor runs for 45-60 seconds but the rear never rises. Using Forscan, I ran the self check and pulled codes C1726 and C1964. All I can find for C1726 is a possible air leak or bad compressor. C1964 is basically stating the compressor has cycled too much which makes sense. The car has 100101 miles on it. Has anyone had a similar issue?

[justbob]

How’s the switch on the watts link?


Sent from my iPhone using Tapatalk Pro

[Turbov6Bryan]

Ran for 60 seconds and not raising, id look into seeing if the solenoids are getting power and ground. The compressor is on, the air goes somewhere... does it put out air?

[Drewstang]

Bob- That was one of my first moves. I adjusted the switch to raise the rear. No effect.

Bryan- I haven't taken the line loose on the compressor to see if its putting air out. I'll try that next. It's making noise like it normally does. Using Forscan for the self test, I can hear the solenoids click in the rear.

[justbob]

I was just curious if the switch was bent or broken internally causing it to think it’s at ride height but if you tried to adjust it I guess not.


Sent from my iPhone using Tapatalk Pro

[Drewstang]

Just and update. Pulled the air line out of the compressor and let it run two cycles. Air came out of the line from the rear which makes me think at least one of the solenoids is opening. The compressor is moving air, but I'm not sure what the output should be. It feels like 15-20 psi or so. I ran it a second time with the air line disconnected and using shop air, I attempted to inflate the rear bags. The first cycle was unsuccessful, the rear did not raise. However the second cycle the rear raised to normal height and turned off the compressor once the height was reached. It's currently holding air with a measurement of 29 1/2" from the ground the wheel arch. I'll measure it in 24 hours to see if there is a change. I'm going to order a new compressor, the bushings on the mounts are shot and the housing is pretty rusty.

[Drewstang]

Just an update, I ordered a new compressor from Rockauto made by Arnott. That fixed the issue.