[frankM_]

Originally Posted by Jazzbass

Pin 85b of the DME relay connects to pin 20 of the DME. The internal circuit of the DME controlling pin 20 looks like this:

Attachment 11865

Transistor T480 is a simple NPN darlington transistor being used as a switch to pull DME pin 20 to ground when activated. For the non-EE types, it's sort of like a ...

Can I ask you where I can find a full schema of a Motronic 1.0 box ?

[ClayPerrine]

Just an add on to this thread. The DME relay evolved from the "Double Relay" used on L-Jet injected 914s. But it evolved badly. In 35 years of running an L-Jet 914, I have only replaced the "Double Relay" once.
And I have had lots of experience with DME relays. I used to work on Porsches for a living. I got lots of 944s, 911 Carreras, and BMWs towed to the shop with no start issues. First thing I did was to replace the DME relay with a test one. About 90% of the time that fixed it.

So I made a replacement. I took a DME relay and stripped the base of everything but the pins. Then I got a pair of sockets for a standard Bosch square relay. With a little wiring, I was able to build a plug in replacement for the DME relay that used standard Bosch square relays.

When I put the 964 motor into my 914, I just rewired the harness to eliminate the factory DME relay, and put in a pair of Bosch solid state relays. I should never have a DME relay issue.

If it will help everyone, I can workup a wiring diagram that will show you how to redo an old DME relay to use a pair of standard Bosch relays.

Clay Perrine

[rothaus]

Originally Posted by ClayPerrine

If it will help everyone, I can workup a wiring diagram that will show you how to redo an old DME relay to use a pair of standard Bosch relays.

Clay Perrine

That would be great.

Cheers
Engelbert