911 3.2 DME Wiring Harness Questions

[johnman001]

I have a 911 3.2 DME Wiring harness that doesn't match any of the diagrams that I have.

Close to the DME plug (where it would attach to the DME itself), there are a couple of connectors that I don't recognize and they appear to be factory. These are in addition to the DME Relay plug and the altitude sensor/switch. One looks like a strange 6 pin molex connector with only 5 positions filled, and the other is what looks like a female RCA jack.

The wire colors are faded.

In the Molex connector there is:

red (ish) - +12v power
purple or grey - ground and to RCA Jack
white - to RCA Jack
white - from cylinder head temp sensor plug
brown - to pin 13 on DME

I had thought this might be something to do with cruise control, but the wiring diagrams that I have (Factory Manuals) never show anything disrupting the cylinder head temperature sensor, and show the cruise control completely different.

It looks to me like for this harness to work, it needs the white wire from the Cylinder head Temperature sensor to be jumpered to the brown wire to DME pin 13, and the rest of the wires isolated and taped off.

Anyone have any experience seeing a harness like this?

There is no plug for an O2 sensor, so I'm assuming it is a Euro Harness. The engine is an 1984. I do not have the DME that goes with it.

I just don't recall ever seeing an RCA jack or this 6-pin molex connector on my other 3.2 harnesses.

Thanks for your suggestions.

[johnman001]

Here are pictures of my mystery connectors. Pictures are worth 1000 words or so they say. Maybe someone knows what is supposed to plug into these connectors.

Thanks in advance!

Merry Christmas or Happy Holidays!

[Tad240]

Interesting for sure. I have no clue but it kinda makes me curious if it could be a custom attempt to alter or modify the CHT sensor output to the DME to possibly control AFR with a rheostat or similar device that would connect to those two connectors. Probably wrong but just tossing out my first thought. Hopefully you’ll get some expert feedback.

[scarceller]

Those are not factory connectors, someone butchered that harness. Only way to know what was done is to figure out where those extra wires go.

I own a 84 car and am very familiar with these harnesses, those connectors are not factory.

One more point: you see all that black tape wrapped around the harness starting at the connector, that's not factory. I suggest you unwrap all the tape.

If you PM me an email I'd be happy to provide a decent schematic of the DME harness that's easy to read.

[johnman001]

Originally Posted by scarceller

Those are not factory connectors, someone butchered that harness. Only way to know what was done is to figure out where those extra wires go.

I own a 84 car and am very familiar with these harnesses, those connectors are not factory.

One more point: you see all that black tape wrapped around the harness starting at the connector, that's not factory. I suggest you unwrap all the tape.

If you PM me an email I'd be happy to provide a decent schematic of the DME harness that's easy to read.

Are you positive? It really does not look hacked, except the wires don't seem to match anything else with the harness. Thank you for confirming.

I have all the factory current flow diagrams and the similar ones from Bentley, and don't find these wires on any of the harness diagrams. I did figure out that they interrupted pin 13 (cyl head temp sensor) input to the DME which seems an odd thing to do, (I guess they were attempting to manipulate the mixture) but they also tied into the power and grounds of the DME which made me wonder if this was something that was done back in the day or not. I've seen dozens of these 3.2's and I've seen many things, but this one is different.

I'll open up the harness from where the wires exit the loom back to the connector housing and see what they did and repair the harness.


By the way, Sal, do you still sell a MAF to replace the AFM on these 3.2's?



Thanks and Merry Christmas / Happy Holidays!

[gerakroo]

For sure not original, for a EURO car the part number on the DME harness should be 911.612.173.07 or maybe the 08.
Normally 13 goes directly to the cylinder head temperature sensor.
Pretty sure to get it working you need to connect the brown and white wire.

[gerakroo]

By the way... nice breakout box !

[johnman001]

Originally Posted by scarceller

Those are not factory connectors, someone butchered that harness. Only way to know what was done is to figure out where those extra wires go.

I own a 84 car and am very familiar with these harnesses, those connectors are not factory.

One more point: you see all that black tape wrapped around the harness starting at the connector, that's not factory. I suggest you unwrap all the tape.

If you PM me an email I'd be happy to provide a decent schematic of the DME harness that's easy to read.

Yes, Sal, you were 100% correct.

I unwrapped the tape and they had cut the harness almost all the way back to the connector. The wires were spliced there. I spliced the wire from the cyl head temp sensor (black/red stripe) and sealed up where they had connected to the power and ground.

I re-wrapped the wire harness and got rid of the mystery connectors. I have no idea why they would want to add this in the first place.

Thanks for confirming that it wasn't supposed to be there, and it explains why I couldn't find what would have plugged into the connectors.

[johnman001]

Originally Posted by gerakroo

By the way... nice breakout box !

Thanks! I made that a while back.

[scarceller]

Yes I still offer MAF for the 84-89 cars

[scarceller]

The USA harness should have 2 brown wires near the DME connector. The Euro harness did not have the 2 brown wires.

The wires had a white connector on each wire, one female other was male. You could plug these 2 wires into each other for inferior fuel.

Not sure if you found 2 brown wires hanging around when you un-taped the harness.

Messing with CHT sensor was a hack back in the day in an attempt to add extra resistance in series with the sensor in an attempt to trick DME into richer mixture. Very BAD idea!

[johnman001]

Originally Posted by scarceller

The USA harness should have 2 brown wires near the DME connector. The Euro harness did not have the 2 brown wires.

The wires had a white connector on each wire, one female other was male. You could plug these 2 wires into each other for inferior fuel.

Not sure if you found 2 brown wires hanging around when you un-taped the harness.

Messing with CHT sensor was a hack back in the day in an attempt to add extra resistance in series with the sensor in an attempt to trick DME into richer mixture. Very BAD idea!

No loose wires where they had the harness cut open and no O2 sensor plug, so all I can assume is that this is a Euro harness, and that they made some kind of hack a long time ago which is now undone.