I need some information on how the secondary air pump.

My main question is, when is or does thing work? Is it doing start up or does it come in intermittent?

Reason I ask is because I have serious issue with mine. For some reason the original one burnt out, it literally stayed on and burnt itself out. I bought a used one from a wrecked srt-6 and put it in and thought all would be fine, wrong.

This one is now stays on and its random. I know that it is on because I guess it starts to whine (think low audible blower whine) until I unplug it.

I pulled the RCM box (is that what it is call?) by the battery and looked at the contacts on the circuit board, they looked fine. They were not cracked. I'll take a picture of it and attach later.

Anyhow, can somebody give me any other things to look for, I know this pump is not suppose to stay on.

 

It should come on with a COLD engine start and run for about 45 seconds to one minute.
It's purpose is to heat up the catalytic converters quickly so we can hug more trees.

The blower is simply that : unintelligent and purely controlled by the RCM relay via the PTCM.
I'd guess there is a 99 percent probability that the relay contacts are burnt / sticking.

( the big orange fuse on the RCM is for the blower )

 

Thanks, ill look into replacing it. The stupid pump does as you say, works for a min then stops, but for some reason later on it comes back on and stays on.

When it killed the last pump, the car was off and it was still sending juice to the pump.

 

Im still failing with this air pump. Seriously why cant this useless thing be tuned out. I bought a new 40 fuse put it in, connect the air pump and it starts running as soon as I plug it in note the car is off, put the old 40 fuse and it is still doing the same thing.

I guess it is not the fuse, something else is wrong as the power is stuck on which leads me back to the RCM, I was hoping it might be a ground but I didnt see any ground connection since the wire is coming out the side of the fender.

Any suggestions.

 

Nobody said it was the fuse.
When you said "Thanks, ill look into replacing it." I had a suspicion you meant the fuse.
The car runs perfectly fine without the air pump working, ignore the red light and get on with your life. It would not pass a State pollution check though.

If the pump runs all the time then it is most likely a stuck relay as has been said before.

 

I agree with 180, my air pump was messing up when I bought it and it was the relay. Mine needed the resoder job though. It threw a light all the time. Pull the relay pack out and clean the points.

 

I'll crack open the RCM and look at re-soldering the air pump relay. The car runs fine I just dont like engine lights, and what if one day that light could mean something else I would know unless I planned on pulling the code one a week.

Thanks for the suggestions, if all else fails I'll shell out a few hundred and buy a new one which is what MB wants anyway. I knew what I was getting into when I bought the thing. Its a German car, if anything goes bad expect to pay big bucks to fix it, I have an audi a6 avant, and an older S Class so its no biggie. I just want to try as many things first, before just saying eff it, new RCM. Thanks.

 

You can remove the little spring from the relay armature and finagle the armature out so you can get to it's contact point and the other one on the relay. Give them a good burnish , clean 'em with contact cleaner and reassemble.

 

I'd bet $50 that the relay armature has stuck, closing the contacts and making the pump run all the time.

The only other thing would be a shorted transistor on the PTCM pulling the relay in, but that would be a very rare occurrence. (And a more expensive fix.)
If the relay is bad, SOMEWHERE on here someone (180?) found a cheap, aftermarket replacement. The relays just solder in - no need to buy a new board!

 

That would be me. I sent Dave 3 of them, gave a few to Max and have 2 or 3 left.

 

Correct, I did a thread on replacing the relays (click) some time back. Replacing a relay should be no big deal to someone handy with a soldering iron. I found the part number of the relays and ala_xfire got some and proved the number in my thread to be correct by replacing one of his. Relay replacement sure beats buying another RCM even a used one which may not be perfect anyway.

They say we should practice the three R's in the conservation of resources, Relay Replacement is two of the them, what is the other?

 

The other R is prolly retry until you get it right.

I'll be diving into this in the morning, took thursday and friday off from work.

 

Update, took the RCM out and looked at the air pump relay it was burnt up nicely. Took some emery paper and cleaned off the crispyness and hit it with some contact cleaner.

I notice on the armature that one of the little circle dots had flatten itself out I guess from the heat so it is like a round pancake now, this was what was stuck as you guys had said would likely be the case. I put it back in the car and started it and the light went out. Im unsure how long this will last as im worried about flatten circle on armature so I'll likely have to replace the whole relay sometime in the future.

For now it is working and ive learned something about german relay's thanks to you guys. Thanks