I had quite a heavy load in the trunk as I headed out for a long trip. A few miles from home I was greeted with the Visit Workshop (airmatic) message. Drove about 400 miles, no sagging of the suspension. After the car sat for 30 minutes (and was light on fuel) I set off again for another 150 miles. No message this time.

When I arrived at my final destination I checked the codes and found 5503 stored (recovery time during filling if central reservoir is too long). Cleared code.

Fired up Xentry just now to run compressor test. First attempt failed and only reached 10 bar. Ran the test again and it passed (14 bar). Ran it a 3rd time and it passed again. Listened for large leaks during test and did not hear any. Again, car is level (even with the load).

Is it likely to be a failing compressor? If not, suggestions as to what else might cause this? I have searched this and other forums and the responses tend to vary a great deal.

 

How long did it take to pass the test?

 

The two times it passed it was about 20-25 seconds I can rerun the test if an exact number would help.

 

Hmmmm? So the cars stance looks right, level and drives ok ?

Sorry, forgot to mention that a 20sec refill is acceptable.

 

Yes, the car stance is fine and level. Drives just fine. I just took it out to fill up the tank and pick up dinner. No issues or error messages.

 

I wanted to follow up on this as it might help someone else in the future.

There were a couple more intermittent error messages that seemed happen when it was cold out. In warmer temps or if I ran the pump a couple times it would eventually work.

I decided to try replacing the compressor's piston ring instead of the entire pump. The motor did not appear to be the problem and I thought after 133k miles that the ring could be failing to seal when cold. I ended up purchasing this kit https://bestofparts.com/parts/merced...-fix-par_28260. It was from the original UK developer and uses a PTFE ring. There are a number of Chinese knockoffs of this, but none could tell me what the ring was made of other than "plastic".

When I removed the cylinder/head assembly I noticed some wear at the top of the bore. It looked like the hard anodizing had chipped off/worn through. Not having a spare, I just smoothed out that area (I didn't take an "after" pic) with fine wet/dry sandpaper, cleaned it all out, and reassembled. The original piston ring was in rough shape. It had obvious wear and small particulates imbedded in the face. The hoses leading to the pump were not cracked and the filter looked clean (I replaced it with a new one anyway).

After I go it back together I ran the pump test through DAS. I expected to have to run it a few times to get the ring to break in. That turned out not to be necessary. It passed the test in less than half the time it had prior to ring replacement the first try. I ran the test two more times and it completed in around 7-8 seconds. Previously it would take around 20 seconds to pass (the times that it did).

I have put over 300 miles on the car since the repair and have not had the error message return. This may not be the fix for everyone, but it is worth considering if you are getting the 5503 code.