DME Power wiring - 12V Constant vs 12V Switched

[frantic]

Trying to figure out what the best way to handle power to the DME Harness should be, I'm using an E46 330i engine harness and after trimming the Auto wiring from it I have 3 Red wires that are all connected to Power to get the motor started and running.

When I have them connected direct to battery, it drains the battery within a day and won't start.

Alternatively I added some relays to the circuit to turn power on to the 3 wires only with Ignition. This stops my battery drain issue, but I wonder if I'm making the DME messed up by essentially cutting power from it completely as if the battery was removed.

I've been trying to track down some wiring diagrams for the E46 330i so I can figure out which wires should be on Constant 12V, or switched. Any ideas? Anyone else run into battery drain problems connecting them to constant 12V?

[82eye]

Trying to figure out what the best way to handle power to the DME Harness should be, I'm using an E46 330i engine harness and after trimming the Auto wiring from it I have 3 Red wires that are all connected to Power to get the motor started and running.

When I have them connected direct to battery, it drains the battery within a day and won't start.

Alternatively I added some relays to the circuit to turn power on to the 3 wires only with Ignition. This stops my battery drain issue, but I wonder if I'm making the DME messed up by essentially cutting power from it completely as if the battery was removed.

I've been trying to track down some wiring diagrams for the E46 330i so I can figure out which wires should be on Constant 12V, or switched. Any ideas? Anyone else run into battery drain problems connecting them to constant 12V?

you can find early car etm's online, but bmw has blocked them from e46 forward. there is a subscription you can pay for access, i don't know if anyone has posted them.

edit : on an e30 the main relay sends power to the dme on pin 36 - constant and on a resistor, and pin 37 which is switched. the main relay is hot all times. wire color for pin 36 is brown, and red/blue for pin 37. motronic 1.3 clears codes when the battery is disconnected, suggesting it gets power at all times, would guess your dme works similar. disconneting power to an e30 dme does not affect it adversely. i'm not sure about a more modern dme though.

[frantic]

Yeah I'm referring to the power going to the engine harness that are not wired through the C101 or into the E30 loom. My DME either way will turn on and prime the fuel pump when ignition is on.

It's more or less should the engine harness be getting 12V constant (But it seems to be draining my battery), or if I cut power am I clearing the DME, Codes, adaptations etc, perhaps not all 3 need constant 12V. i'll add some pics tomorrow with wire colors I'm referring to. They are power wires going to the harness with the DME Relays, and the little Black fuse box..

[82eye]

if i'm reading it right the dme and main relay get power direct from battery on a fused wire. it's hot all times. should be nothing in the rest of the loom until a start signal. there should be a hot all times pin on the fuel pump relay, i believe it gets it from the main. i could be wrong on that last bit.

[TobyB]

www.bmwteka.com might help...

t