Having done some searching here, I think I've exhausted all reasonable options so am now looking for help.
I have a 1997 SLK230 R170 with clutch-type supercharger system.
When I first bought the car, the supercharger was (mostly) working for first few minutes then (mostly) giving up once the car reached temperature. Sometimes it wouldn't engage from cold start, sometimes it would randomly work for a few minutes whilst warm then give up again. Now it doesn't work at all, even from a cold start.
If I disconnect supercharger clutch plug:
* Resistance of clutch coil is about 4.4 ohms
* Resistance of ECU end (battery disconnected) is about 69k ohms
* When ignition is on 2 or engine running, I meause 12V across ECU side of supercharger plug
* Yet SC clutch does not engage, can't hear a click, turns freely by hand with engine off, ignition on 2 (12V measured from ECU)
Recirculating air flap does nothing (always open). Measure 12V between power and ground, 0.5V between signal and ground from ECU end. Air flap doesn't make any noise, unlike the air intake throttle body.
I tried swapping the air flap for another one off eBay, still nothing. Can't be sure the replacement flap works either though.
One of the 15A fuses on my K40 was blown (sorry can't remember which one, but think it might have been the 4th from left (2nd from right) if looking at it such as the 40A fuse is at the top.
Replacing the fuse hasn't changed anything, hasn't blown again either.
I did take it in for diagnostics, unfortunately the garage wouldn't give me a list of fault codes. All they said was that it showed a recirculating flap error and that they ran a test of the flap using STAR and it wouldn't respond. They also cleared all the codes so I can come back later to see if any have re-appeared.
Unfortunately this car doesn't have OBDII (too old) and I don't have a multiplexer / interface box that can talk to it.
Based on the garage's advice I bought the eBay replacement flap/actuator (1110980009
) but as I said it doesn't appear to have done anything.
Does anyone have any further advice? Is the clutch most likely not working?
Probably next up I'll try connecting the clutch straight across the battery. How have others managed this? Using alligator plugs? Directly on the pins or by cutting the wire insulation?
I might also rig up a test of the two recirculating flaps. I understand it should be 12V, GND and a pull-to-ground 45Hz PWM signal right?