K5 Relay and fuse 17

[fred633]

My K5 relay is not pulling down. I have power on 30, 86, and 85. I can jump 30 to 87 and it will power fuse 17. Anybody have an idea what is going on. I have swapped out the relay with a known good one.

[RonW]

You say you have power on pins 30, 86 and 85. I assume you mean you have 12V relative to ground at all those pins. 12V should only be at pin 85 while cranking. At other times it should be at 0V. This wire uses the starter motor actuation coils as an effective ground. If you have 12V at pin 85 when you aren't cranking then that wire is probably floating, and the relay's coil is pulling it to 12V.

• Does the K7 relay actuate? On the 635CSi, both K5 and K7 are actuated by the same signal, so both should turn on and off at the same time.
• With both K5 and K7 removed, see if you have continuity between the black & yellow wires at pin 85 in both relay sockets.

[demetk]

What car are we talking about?

[fred633]

633

[demetk]

And the 635 ETM diagram is relevant here?

[fred633]

It is the only one I have. If you have one for a 633 I would be interested in the link.

[demetk]

This should have it: http://wedophones.com/BMWManualsLead.htm

Looks like the 633 and 635 share the same diagram for the unloader relays. That black/yellow wire is turned into a ground via the ecu. That's how the unloader relays get activated. So check pin 4 on the ecu connector for ground with the ignition on.

[RonW]

That black/yellow wire is turned into a ground via the ecu. That's how the unloader relays get activated. So check pin 4 on the ecu connector for ground with the ignition on.

According to the '83 633CSi ETM that wire is "grounded" through the starter motor actuator coils. The black & yellow wires from pins 85 on the relays join together at pin 8 on connector C101, which is a 17-pin connector on the right side of the fusebox. Those wires are therefore connected together - that's why I asked whether both relays switched, and suggested you test for continuity between pin 85 on the relays' sockets.

[demetk]

I see pin 4 at the ecu as the ground point.There is no note on pin 4 in the 84 or 85 etms but there is a note in the 86 etm to that effect.

carry on.