Tukas

Hello everyone,

I've been searching everywhere for the explanation regarding the air pump connectors/wiring but haven't found anything relevant.
I am trying to find out what the problem is because the compressor seems not to be producing enough pressure.

Recently I've changed the compressor to brand new, the valve with red/blue hoses, checked all hoses for cracks, changed the bags to the brand new but the problem still persists.

I've tried to take out the intake hose and output hose and put my finger on both ends - it sucks the air, but pretty weak and I can without any problems shut the output with my finger. I think it shouldn't be like that, right? Seems that it's not producing enough pressure.
Checked the voltage with a voltmeter and +14+ volts are coming when the car is running and I manually switch the pump on with INPA.

But I see that there are two connectors, one with wide wires, that's the + and - and another one with smaller wires - what that other connector is doing and what's it's purpose? Can it be related to the problem?

I'm lost here and ordered another pump which I am getting tomorrow because I think it might be a coincidence and the new pump is bad, the supplier said that it will take it back and give another one.

I will appreciate any help!

EDIT: 2007 LCI e61 535d 210kW LHD

Thank you.

Sincerely,
Tukas

seanjordan20

Are you getting OEM pumps or aftermarket? I don't understand why owners ask for help and don't think the year is just as important. Can you let us know the year of your car also

Tukas

I am sorry, it's 2007 LCI e61 535d 210kW. And I am getting the aftermarket one since OEM is pretty expensive.

seanjordan20

LHD or RHD

Tukas

It's LHD.

Greggo

The two heavy wires are Power and Ground. The two smaller wires are the CAN bus which receives signals from the control unit to inflate or deflate the left or right air bag. Each bag is controlled separately.

Correct voltage does not mean there is enough current. See quote from repair instructions below.

There are three relays in the trunk, under the spare tire. Two salmon and one aqua, if memory serves. If they have not been moved around, the relay closest to the front of the car is the one in question. They are not expensive, would recommend replacing all three. They are not marked.

Look for corrosion on the contacts. If there has ever been water in the spare tire well, all of the connectors and modules can be affected and cause some very strange things.

"Important!To prevent premature failure of the air supply unit, it is essential to replace the air supply unit relay as well!"

Tukas

Thank you for your reply.

Last summer I have spilled a lot of juice in the trunk and I had problems with three of the control units, including the air suspension one.
So, I've changed the control units and the green relay back then.

Everything was fine until now. So when the problems started again I've checked those connectors and the relay - evrything seems to be clean there. So, I've dissasembled the relay but inside of it it's really clean and there are no signs of corrosion or water.

Maybe some wires are starting to crack from the whole harness? But, as far as I looked they seemed to be fine.