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Samson 10-07-2020 10:52 PM

Wiring harness short
1 Attachment(s)
So I had a short in at the ignition switch that fried the wires on the main harness. What kind of nightmare is this to replace? Looks like a new one is $1K, or off a donor car.

If I did an engine swap, would I normally have to swap the whole wiring harness anyhow? Cause if that's the case I'll just try and get an engine and the side stuff.

Or... Someone told me they had a similar issue, and were able to trace the wires back and replace anything damaged with fresh wires. If anyone has done this, or knows of a guide to the harness so I can pull this specific part that would help.

Anyone in WA know of a mechanic willing to tackle something like this?

Uhg, I'm really bummed. Here's a pic of the location I'm talking about. Burnt wires run up as far as I can see them.

1999 318ti

J!m 10-08-2020 02:57 PM

Do the wires run through the firewall to the engine compartment?

An engine harness is seperate from the chassis harness. You need to repair the chassis harness. I suspect there was some chafing of the wires where they pass through the firewall, or possibly other damage from aftermarket radio installation for example.

Least expensive option is to chase it back to the source and repair the bad wires.

Note they will show heat distortion far away from the actual short point, but as long as the insulation is in tact it will be fine. Solder and shrink tubing (plus skill) will be needed.

StoneWheelRacing 01-09-2021 04:34 PM

Wiring Harness Swap
While putting an M52B28 into our '98 TI we purchased a '99 M3 manual trans engine harness with a few burned wires for the fuel circuit.

Harness seller says the wrong relay was put into his M3 harness and the wires for that socket/circuit burned up.

Our M52 donor was a '96 OBDII cabriolet automatic. I know, or have been told, an auto harness works in a manual car but didn't want any extra unused wires, plugs etc... hanging around.

Ill be pulling the same circuit (fuel wires, socket terminals, sockets etc...) from the 96 auto harness and setting it into the 99 manual harness.

Hopefully it arrives today so we can get started. Have solder and shrink tubing ready to go.

I do plan to pull the terminals out of the relay sockets so I can re-shrink tube the enter harness for a more factory look.

StoneWheelRacing 01-09-2021 04:37 PM

Wiring Harness Swap
Sorry about that damage. I'd give you my donor car chassis harness but I just junked it.

Samson 01-09-2021 05:08 PM

I actually totally lucked out. Looking into it, the wire that died was a ground. Replaced it, reinstalled everything and the car drives perfect. Not I just gotta find a S52 haha

StoneWheelRacing 01-09-2021 06:04 PM

Great news!. Yeah, that's why we just settled on doing a M52B28. Too easy to get and Riot Racing has the same cams as S motors for like ~$500.

M52B28 starts at 190 hp but with cams and DME tune, and other stuff should get 300hp at the wheels.

J!m 01-11-2021 11:39 AM

300 at the wheels is a tall order for an S52 with about ten grand thrown at it. But it can be done.

Please post your tuning results if you can get 300 at the wheels with a cam and tune on a 2.8! (In a new thread since I just derailed this one)

Samson 01-11-2021 01:12 PM

I'd be happy with 215 and the S52 haha. Gotta find a motor and an able, affordable mechanic first.

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