Mystery electrical problem
05-24-2009, 09:31 PM
#17
Rennlist Member
So, like the OP states, a ground could be the problem. I don,t think that a cab top CU has any magic going on, but they do have lots of micro switches connected to flimsey linkages. Thats why I ask the year of the car. A 993 has a totaly different cab top control than say a 996/997. Lots of cab top problems almost always boil down to microswitch adjustment.
I would most certainly agree with the above posts that,given the complexities, proper voltage in and out of the CU should be easy to nail down. My point with the volt meter is that there is a fair amount of "micro" voltages doing the communicating inside these CU. ~5v is normal. If one was looking for 12v then... instant snafu. And even then lots of components use pulse width modulation(PWM) in which case the garden variety volt meter will average the signal. A good analog meter is better in these cases.
Anyway. Good info from everyone. I would like to know the substance behind the dealer's diag.
Oh, Dshepp: I hooked up my Von Schweikerts and listened to Power Windows-a gold standard in my CD player. So much style without substance, So much stuff without style...
Hope everyone is having a great holiday weekend.
Scott
I would most certainly agree with the above posts that,given the complexities, proper voltage in and out of the CU should be easy to nail down. My point with the volt meter is that there is a fair amount of "micro" voltages doing the communicating inside these CU. ~5v is normal. If one was looking for 12v then... instant snafu. And even then lots of components use pulse width modulation(PWM) in which case the garden variety volt meter will average the signal. A good analog meter is better in these cases.
Anyway. Good info from everyone. I would like to know the substance behind the dealer's diag.
Oh, Dshepp: I hooked up my Von Schweikerts and listened to Power Windows-a gold standard in my CD player. So much style without substance, So much stuff without style...
Hope everyone is having a great holiday weekend.
Scott
Scott: great album:
It's hard to recognize the real thing
It comes along once in a while
Ed makes a good point in that some of those "other" fellows may have some specific threads relating to your situation.
STILL: you are most welcome here. Oh yeah: be sure to use (get) a True RMS meter, as you will be prepared for most things, come PWM time.
Best of luck and do keep us tuned in. I'm interested in seeing these circuits and how they're "handled"...sounds like TTL stuff with commom emitter configs,..allowing a ground through via +5 VDC on the base.....??
STILL: current drain? with the ignition off? mmm? I, too, would like to know exactly what the dealer "found". Not sure,..keep at it.......hopefully, we'll all learn something from this.
Best to all,
Doyle
