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super charger issue

823 Views 2 Replies 3 Participants Last post by  Jet Wrench
HI 73 year old with little computer or electrcial know how has got a problem with super charger
checked K40 card is as new no burning
checked Maf very clean
checked throttle body very celan no carbon
read about this Mosfet have not a clue where that is
this grandad is stumped spent working life has a mech.maintenance engineer
so prepared to tackle any mechanical issue though not has able as you younger guys
Probably posted in wrong place perhaps a Link for newbies would be helpful
every time I have tred to post your talented master sergeant moves it to god
knows where
super charger clutch does not engage even though pulley is turning
would try seprate feed to cluch but afraid of damge to ECU
be very grate if you have Super charger for Dummies
thats how I feel
Any help gratefully recieved
All the best
Paul UK.
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Welcome, Paul. IIRC, 99's have a electrically operated SC clutch, the Motronic (ECU) turns it on and off as needed. At idle, the clutch is not engaged. With the transmission in park, you can move the throttle by hand to increase the RPM to ~2000 and the clutch should engage (you'll see the inside part of the pully start spinning).If it doesn't, the next step is to determine if the Motronic is trying to engage it. There is a two-pin barrel-shaped connector on the front of the engine near the SC, you can measure the voltage here to confirm/deny. It's a common failure for the butterfly valve atop the air filter to fail, I think the Motronic refuses to engage the SC if it smells a rat there. A quick sanity test of the butterfly valve is to disconnnect the hose (the one with the spiral wire) so you can see it, then turn the key off and back on a few times. You should see some slight motion of the butterfly. Inspect the wiring carefully to the butterfly valve since it gets stressed when the air filter is replaced.
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SC not engaging

Hello Paul,

EFair gave some great advice on SC operation. If you have 12VDC at the SC plug, make sure it has a good return to ground at the plug. You can also check the clutch with a 12VDC power supply to check the clutch operation. The wiring on these cars is getting old now, and heat can cause issues over time. After doing major work on mine (same year), I also had SC clutch issues after re-assembling. The connector was not seated well. It's a good idea to clean the connector with some alcohol or electrical connection cleaner.
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