Which b35 harness to buy?

[Click]

I don't wan't to cut and splice a near 25 year old i harness when I do my swap. I can get parts at cost at my local bmw dealership. I have a b35 from a 92(i think) 735i and 260/6 from a e34 535i. I priced an e34 harness a few months ago (i forget which one) and it wasn't near as expensive as realoem lists them, I think it was like $400 or so.

Looking at a manual 91 535i you get these options.

01	CABLE HARNESS OIL LEVEL SWITCH	OEL/GEN	1			12511724026	$78.05		
01	ENGINE WIRING HARNESS DME+EML		1	08/1990		12511732008	$901.02		
01	ENGINE WIRING HARNESS DME		1	09/1990		12511724722		ENDED

A automatic 91 535i you get

1	CABLE HARNESS OIL LEVEL SWITCH	OEL/GEN	1			12511724026	$78.05		
01	ENGINE WIRING HARNESS DME+EML		1	08/1990		12511732008	$901.02		
01	ENGINE WIRING HARNESS DME+EH		1	09/1990		12511724735	$710.95

Looking at a 91 735i (only automatic) these are your options

01	ENGINE WIRING HARNESS DME+EH		1			12511714048		ENDED	
01	ENGINE WIRING HARNESS DME	MOTRONIC 1.3	1	07/1988		12511724234	$679.87		
01	ENGINE WIRING HARNESS DME+EH		1	09/1989		12511732683		ENDED

Doing the research, EH stands for electrohydraulic, referring to automatic transmissions, which would likely have more wiring on it than I would need. And EML stands for "Elektronische Motorleistungsregelung" which means it is for drive by wire and I would assume it is for those m30s with the electronic throttle body, also something that I don't want.

I did some further researching and found if you look up a 89 535i. you have these options.

01	ENGINE WIRING HARNESS DME+EML		1		08/1990	12511719615			
01	CABLE HARNESS OIL LEVEL SWITCH	OEL/GEN	1			12511724026	$78.05		
01	ENGINE WIRING HARNESS DME	MOTRONIC 1.3	1	07/1988	11/1989	12511724234	$679.87

I read here the 5er harness may not reach into the factory location. But people reported that the e32 harness does. I do not know what year/trans Jean's harness came from but I did look up a manual 89 735i for reference.

01	ENGINE WIRING HARNESS DME	MOTRONIC 1.3	1	07/1988		12511724234	$679.87

The same part number as the 89 535i. Obviously the later wiring harnesses have different numbers and I am assuming possibly different lengths. One might also note that this is the non-EH harness from the 91 735i, which was automatic only, which I am assuming is a manual harness.

I'm thinking the 12511724234 harness is the best option. Any thoughts?

[csermonet47]

If you are going to buy a new harness, get an M20 one. Trust me. It is way easier and cleaner than running an M30 one. You have to lengthen a max of two wires and everything fits your bay perfect.

[yert315]

^ I disagree. I tried the m20 harness and it looked like poop. The b35 harness fits nicely in the engine bay and is cleaner all around. Not to mention it was meant for The m30 engine to begin with.

Personally I would run a b35 manual harness. That way you won't have the trans wiring laying there.

[csermonet47]

Probably weren't doing it right ;)

[yert315]

touché. well done sir.

[CorvallisBMW]

M20 harness is really, really easy and fits exactly the same as the m30 harness, but has fewer unneeded wires and plugs. If you get the black plastic injector harness cover from a junkyard 535i/735i for $5, you can use your old m20 harness and have the exact same fit/finish but for $395 less than buying a new m30 harness.

[WatchMyDrift]

I used the m20 harness only because i didnt want to change the c101 conector on the fire wall. trying to figure out how to connect everything seemed like a bitch. plus in the m30 swap write up it suggested to use the m20 harness to avoid this problem..

[yert315]

^ misinformed. The b35 harness will plug right into the e30 c101.

[WatchMyDrift]

really.... i think it depends on the year..... idk.

[yert315]

Afaik, all e30's had the round c101 plug. Not 100% on the 84/85 model years. Otherwise a late model m30 harness (motronic 1.3) will plug right into the e30 c101.