Hoping our related cousins on this site can be of some help in finding this relay or whether it is likely culprit of my problems.

I just bought a SLK32 and noticed a marked drop in performance when warmed up that comes and goes. From reading threads it seemed probable the IC cooling pump had gone, indeed the 5a fuse had blown. Replaced the pump with a bosch uprated pump and the fuse but still no change. Fairly sure it is not getting any power. Read elsewhere that the relay often needs changing at the same time. A MB dealership were pretty unsure what relay it was but guessed it was a general engine management relay at over £114 + vat. Needless to say they didnt have it in stock either.

Could anyone tell me where the actual relay is located? I would like to pull the relay and then get a part number and check it out.

any help much appreciated

 

You could try the IAT sensor first.............it is a $20 part over here, not sure what it will be in the UK
It is the sensor that sits in the y-pipe, and if it is defective it will prevent the SC from engaging.
Never heard of the relay problem over here ...............

 

The supercharger is definitely engaging when cold, the car accelerates like a scolded beast, then when its warmed up the sc fails to engage and performance drops, give it a few minutes and the sc engages again and accelerates well. I've been unable to detect any power to the ic cooling pump and so hopeful that its just that not doing its job. Somebody on MB forum said that MB used to change the fuse, relay and pump ALWAYS together....hence why I'm trying to locate the relay.

I will try changing that IAT sensor though if i get nowhere with the relay search, thanks for your reply and advice, nice to know that I can come to this site for advice,

 

No problem...............
I had an IC pump go out, and just changing the pump was enough to fix it. I haven't heard of anybody over here having to change any relays, but have heard that the IAT sensor can go bad. It's still early over here so I'm sure there will be someone around soon who can shed some more light on this issue, as a few of the members here actually have (or had) SLK's..................

 

It might be associated with the relay or faulty wiring as the pump fuse wouldn't blow when the pump goes bad.

 

It's the relay I am looking for, pretty sure there is one as if you look at the following link for a C32 this chap had troubles because of his

DIY - Intercooler Pump Replacement - Page 3 - Benzworld.org - Mercedes-Benz Discussion Forum

Just finding which relay it is then hopefully can check/replace it and maybe solve my problem

Thanks for the reply

 

Did you make sure that you had ALL of the air out of the system after changing the pump?

Chris

 

No , to be honest I was hoping when the pump ran it would help bleed the system with the expansion tank cap off, but I dont seem to be getting any power to the pump, couldnt detect any power with multimeter or feel the pump vibrate which I hoped it would do if running.

How do I bleed the system then? Looks like I will need to do that anyway, thanks for letting me know, thanks, Chris

 

you can hot wire the pump to bleed (and then try to verify that the iat sensor is not the culprit).

both of my laptops that have STAR (and all of the schematics) had their batteries go dead this weekend .... when one comes up, I will look for the relay and come up with a couple of test points for you.
Chris

 

thanks, that is a good idea, I was contemplating wiring the pump to be on all the time the ignition was on as a last resort but no harm in doing it until I finally find the correct fix, sometimes the obvious escapes me entirely.

So will run the pump full time for now, and I much appreciate your help looking on Star when you get chance to do so, regards, Chris

 

here is the part of the schematic that shows the entire IC pump circuit. It is designated as "M44".

The relay that you seek is part of the "N65" Pulse Module. it is located in the same box as the fuse (drivers side on real cars ... passenger side on yours : )

However, I have NEVER ever heard of this (relay) being the failure. with rare exception, the pump fails (fuse blows) by 20,000 to 30,000 miles AND replacing the pump and fuse solves the problem.

Worth noting on my 1st SLK32 (which I bought at 30,000 miles) the pump was not running when I bought it. the fuse was blown and I replaced it (fuse only) ... and it worked (until 50,000 ?) when the fuse blew agian ... once more I replaced it (fuse only) and it lasted for more than 10,000 or 20,000 additional miles until it blew one more time (and this time the pump actually had failed) So. I finally replaced the pump for the FIRST time near 80,000 miles. NOW, on my 3rd SLK32, I bought it with 17,000 miles AND ITS FUSE WAS BLOWN ALSO when I bought it. I replaced the fuse and have put 1,000 miles on it since and it is still working fine. MY POINT... while this part does NOT last the life of the car, I Suspect it is slightly under-fused and often prematurely replaced. (I seem to recall a mention somewhere that a higher value fuse is used in other models, but never looked into it.

Hope the schematic helps,
Chris

 

if you want to make your pump (temporarily or indefinitely) run whenever your car is running (key position 2 and 3) WHILE retaining the fuse protection for the pump wiring, just tie together two wires on connector E of the N65 module (pin 2 pink/red to pin 7 red/blue) refer to the schematic I supplied for more info (this will bypass the relay that you are having suspicions about)

Chris

 

Wish I had tried the fuse first, but I am guessing that my problem lays with the relay as the new pump should be working with the fuse changed. Thanks for your help anyway will temporarily wire it to work all the time as you described in your last post. Hopefully it will be obvious which one is the relay when I do this and I can take it out and get it checked/replaced. Will get there in the end either way, especially with all the help from the forum.

Thanks again guys

 

I believe that the relay is soldered into the pcb of the pulse module. Like I said, tie together pins 2 and 7 of connector E to bypass it.

until you get nearly all of the air out, the system in nearly non-functional. putting a clear hose from the "t" in metal piping on the front of the SC (in place of the 8mm black hose) and then running it into the top of the reservoir should work.

Chris

 

These may not be the latest and greatest, but here is some info on bleeding with more detail. As in most cases, Woody has given a great explanation for the best method (post 4) also note info on the factory method (post 2). With the jumped wires (pins 2 and 7 of connector E, N65), you should be able to do this (without need to run the engine) by turning the key to position 2 "run"
https://www.crossfireforum.org/forum...ps-itself.html

Chris

 

Thanks for all the great info, will get on with it in next couple of days and report back so you know what happens, thanks again Chris

 

also note there was a service bulletin, replace the original 5 amp pump fuse with a 7.5 amp fuse.

 

Now that makes sense ... how come i never saw that?

Chris

 

was on benzworld pretty sure, with a link to MB article

 

standard MB practice for a blown fuse was to replace the pump until they found out surge current was tripping it lol