so my 2004 A8L sagged everywhere
compressor barely alive

bought an online refurbish kit: included piston ring, 2 bolts, two gaskets.
all you really might need is the piston ring. the other parts were reuaseable.

took the compressot out and bench tested. it was weak.

did the refurbish and the air blew out like the force of a hair dryer on medium.
AND some water blew out ! no idea where that came from but the piston and cylinder were dry. nothing told me there was water in the drier compartment.

but compressor back on car....nothing. it stred for 10 seconds and quit.

car is up on 4 axle jacks. yellow suspension light flashing.

going to bench test it again.
not sure whats going on.

fuse ? relay ? wiring from the vehicle into compressor ?

stumped.

 

A failing compressor usually burn the relay contacts and/or blows the compressor fuse.
The relay should be in the underdash relay panel, to the left of the steering column. The relay you want is J403 and the p/n on the original is 8K0 951 253A. I think the replacement will be 4H0 951 253A (unless it's superceded again). The fuse should be a 40 amp maxi-fuse just below the relay. The relay MIHT be the top left one in the panel but don't quote me on that!

 

Pump back on and connected in mock up

Start car. Yellow error light flashes from start

Pump comes on 30 secs later and stays on for about 20 secs.

Pump goes off. Yellow suspension light flashes whole time.

Bagpipingandy, who has been a tremendous help, suggests disconnecting the temp sensor as this was one of original faults

Pump pumps. No bubbles anywhere so far

Wondering why pump starts then cuts out.

All 4 ride settings now stay red as options from start to finish.

Car is up on axle stands all four points. Not in jack mode.

I'm thinking I put it on the ground now to try and isolate:

Strut ?
Temp sensor ?
Relay?

Cus to me pump is doing what it should.

 

this did not happen in my case