Fixing dodgy wiring options

[zinc]

I recently got a 1989 325i with a stock M20B25 and ECU etc, build date is 7/1988.

I took a quick peak at the wiring under my dash and it's a horrendous mess of aftermarket alarms etc hacked in. Not even sure where to start so I'm just pretending I didn't see it for now.

Engine bay is also a mess but main issue is many of the plugs themselves have disintegrated in addition to the random unknown wires that don't connect to anything. Fuse box has also seen better days and the AC fuse melted pretty bad and appeared to have some random copper strips jammed in to make a good connection which I've fixed up and re-melted back into being servicable shape.

That said it does (or did before I took it apart) run fine despite the 37 years of people messing with the wiring.

Half considering the nuclear option of trying to rewire everything from scratch so at least I'd know what everything is, but that'd also mean it'd be off the road forever.

Original engine harnesses (real OEM says 12511724070) are NLA right so what are the options:

1. Get a donor OE junkyard harness in semi-decent condition, take the plugs + sections needed and repair existing harness, methodically go through and figure out what is junk somehow
2. Wire from scratch, maybe with aftermarket ECU, presume that would mean full engine/dash out
3. Cross reference with official wiring diagrams, remove anything non-standard, patch it up as best as possible and accept it as it is, if it works and isn't broke, don't mess with it too much

I want to learn more about wiring but at the same time would like to drive this thing in the near future.

Will be option 3 and pretending I didn't see it for the foreseeable till I get some engine bits done but at the same time knowing it's a mess is going to annoy me and will need to be fixed eventually.

If you can just get replacement plugs somehow that would help to patch up the existing loom and maybe will replace the fuse box. Can you get replacement plugs anywhere or is anyone making aftermarket looms for stock i.e. non-engine swapped motors?

[max.rodriguezzz]

ok so obviously you're excited and want to drive and enjoy the car (rightfully so) but if you're going to tackle this the right way, you might have to do it the long way.

you technically could get replacement connectors, I'm not exactly sure if you can get the connectors themselves brand new. I'D THINK the most realistic route to go would be to harvest them off of a donor harness/car. This would also mean you would need to depin/repin said connectors, so you'd have to get the special tool to do that, as well as do it right so the wires actually stay in the connector snug. or cut/splice but then youd have a spliced up harness, if that matters to you.

Id be reaaallyyyy cautious about the fuse box's current state. I've seen lots of accounts where e30's have burnt down/caught on fire from electrical fires that was caused by bridging wires in the fuse box or somehow fuse box contacts shorting. Personally, I'd keep a fire extinguisher in the car JUUSSTT to be safe. better safe than sorry.

to cover your point about fixing the fuse box, unfortunately, the entire chassis harness and fuse box is one assembly. From the headlights, all the way to the tail lights. So to replace the fuse box itself you'd either have to depin and repin every single terminal in the fuse box, or swap the whole harness.

in order to swap the whole harness you'd need to remove everything out of the dash, pull the dash itself remove the heater core box, remove the seats front and rear, pull the carpet, drop the gas tank, and remove both bumpers. Basically would have to strip the entire interior to swap the harness. You can leave the engine in as the engine harness is different from the chassis harness.

first things first, I'd trace back all of the clearly aftermarket wiring and see where it goes too/how hacked up and spliced up things really are, assess the damage as best as you can.

assuming its pretty (subjective) bad, you'll then be faced with making a few decisions-

- do you want to keep a hacked up spliced up harness?
- how "proper" of a repair do you want to do?
- how long are you ok with having the car off the road? / would you be willing to make that sacrifice to do the repair "right"?

personally, I'd advise against rewiring everything yourself from scratch, theres a looooooooooooooootttttttttttttttttttttt to do it, but if you're willing and have confidence in doing it, props to you.

at the end of the day everything will be fixable, may take some time and effort, but you got this

if youre interested in seeing exactly how much goes into removing the harness / just exactly how the chassis harness removal is even conducted, @ TheMaskedDriver on youtube has a good in depth video going over a full e30 teardown & chassis harness removal - https://youtu.be/QmUMTYwCLBA?si=-fQdufDEvLlAbDAx

Good luck ! :)

[zinc]

Id be reaaallyyyy cautious about the fuse box's current state. I've seen lots of accounts where e30's have burnt down/caught on fire from electrical fires that was caused by bridging wires in the fuse box or somehow fuse box contacts shorting. Personally, I'd keep a fire extinguisher in the car JUUSSTT to be safe. better safe than sorry.

Yeah good idea tbh, I'll get one. Attached a photo of where I removed a melted fuse. The melted one was rated at half the amps of what it's meant to be from factory, but this car has a R134A conversion so not sure about that. A/C stopped working one day and I pulled a blob of melted plastic out as well as what looked like some random copper strip to make a connection. Have some documents that say it melted before so I think it might have been a half-fix. I managed to re-melt it back into where it can hold a fuse without needed copper strips to make a connection and put the stock amp fuse back in.

to cover your point about fixing the fuse box, unfortunately, the entire chassis harness and fuse box is one assembly. From the headlights, all the way to the tail lights. So to replace the fuse box itself you'd either have to depin and repin every single terminal in the fuse box, or swap the whole harness.

I've seen a video of someone doing it, looks tedious but it is possible at least.

you technically could get replacement connectors, I'm not exactly sure if you can get the connectors themselves brand new. I'D THINK the most realistic route to go would be to harvest them off of a donor harness/car. This would also mean you would need to depin/repin said connectors, so you'd have to get the special tool to do that, as well as do it right so the wires actually stay in the connector snug. or cut/splice but then youd have a spliced up harness, if that matters to you.
[...]
in order to swap the whole harness you'd need to remove everything out of the dash, pull the dash itself remove the heater core box, remove the seats front and rear, pull the carpet, drop the gas tank, and remove both bumpers. Basically would have to strip the entire interior to swap the harness. You can leave the engine in as the engine harness is different from the chassis harness.

I'm thinking probably replace the whole harness would be the best thing to do, but the problem is finding the right part numbers.

RealOEM lists 12511724070 for the engine harness with the build dates from 05/1988 to 09/1988 and 61111385505 with dates 09/1987 - 09/1988 for the body harness. Assuming you need to get a matching harness and you can't mix and match years that's looking for a pretty specific part number/year. Maybe the plugs on earlier/later models are equivalent and could be used. Is there any info on wiring differences between years?

Can keep on eye on eBay etc and see if any come up that look semi-decent.

at the end of the day everything will be fixable, may take some time and effort, but you got this

if youre interested in seeing exactly how much goes into removing the harness / just exactly how the chassis harness removal is even conducted, @ TheMaskedDriver on youtube has a good in depth video going over a full e30 teardown & chassis harness removal - https://youtu.be/QmUMTYwCLBA?si=-fQdufDEvLlAbDAx

Good luck ! :)

Nice one, thanks.

Fuse before:


Fuse after (highly professional fix - but it at least makes a connection now):