No power to K7

[Das Delfin]

what's up guys. Trying to troubleshoot my friend's '87 325i 4 door. His blower motor isn't working and we've traced the problem to a lack of voltage across relay K7.

There is continuity between the main battery positive cable and pin 30. The volt meter reads 0.03V across the pins of K7, as well as across K7's pin 87 and the main battery positive cable.

I opened up the fuse box and traced the pin 87 ground as a black/yellow wire through the firewall along the wire loom up to the blue plug that plugs into the cluster. (btw the car is half taken apart, no motor, no anything basically. But there is an intact heater box). With the cluster plugged in the volt meter reads 0.38V across K7.

We cleaned and sanded a few arbitrary grounding points...

What I'm wondering is what can cause this? I looked up the ETM and can't find much about the wiring between the battery, K7, and its grounding point.

Fuse 20 doesn't blow, so I'm wondering what could be shorted?

The ETM suggests if taking a zero voltage reading at fuse 20/K7, to check a short at the yellow wire (the wire from the "low" setting on the HVAC fan switch, to the AC/Recirc switch, and to the blower resistor (so essentially the main power wire)), but I'm wondering wouldn't a short cause fuse 20 to blow? Anyway it wasn't something I had time to track down this evening.

The AC/Recirc switch does not light up, but I can hear the AC Evap temp relay switching on (however the recirc vents aren't connected, nor can you hear the servos moving when the recirc button is pressed.

Any suggestions? Kind of a hard one. Thanks in advance

[jlevie]

You will find that tracing the circuit to K7 using the BMW ETM will be helpful. you can get it from http://wedophones.com/BMWManualsLead.htm

[Das Delfin]

^ thanks. I downloaded that a few years ago. The problem is that I can't find the connection from the battery to K7, or K7's pin 87 grounding point.

[Das Delfin]

I dug a little deeper and it looks like K7 and K5 are grounded through the starter. Given that this car came without a motor/tranny (planned to be the recipient of an S50), and therefore doesn't have a starter, it makes sense that there is no complete circuit for K7 and fuse 20. Hopefully installation of an S50 will fix the problem! :)

[M-technik-3]

You are not going to have pwer windows as well, I am in the same boat, bosch no longer makes a proper Starter for an e30 M3. The solenoid is supposed to have 4 poles and they now only have 3.

[jlevie]

I don't agree. Early E30's had a two pole starter (main power & solenoid) and later E30's had a three pole starter (main power, solenoid & unloader). On early E30's with the two pole starter the unloader circuit was strapped to ground. E30's from 8/87 had the three pole starter and the unloader circuit went to the unloader pole of the starter. Your can use the two pole starter in place of a three pole starter by grounding the unloader wire. That also works if the unloader switch fails when the starter is otherwise okay. Just don't have the HVAC blower on high when starting a cold engine in cold weather