Third wire to the starter, what does it do?

[DaN]

I just installed a starter from an 87 325e into my 90 325i. And now the power windows, and blower dont work with the car running, but they work with the key on engine off.

Im curious what the second small wire (not crank signal to solenoid) does thats attached to the starter, I read that it has something to do with the main relay, is this true? Is is supposed to have power at all times, or ground.

Is this a parts compatibility issue?

[rs4pro3]

Attach it to the same termnal as the Black/yellow wire. That third wire is a ground for the unloader relay, without it the windows and some other functions won't work.
FYI a 325e starter isn't as powerfull as a 325i starter(for some off reason, the KW rating in the ETK is different between them)

[Jordan]

Higher compression requires stronger starter.

Some of our race motors we put in 2002's with 10.5-11.5 CR crank VERY slow, borderline wont start its so slow. Stock starter isn't up to the task.

[rs4pro3]

up to 86 eta 1.1KW after 86 eta 1.4KW then the I's are 1.4KW so I guese your 87 one will be up to the task. I've always wondered why they stuck a weaker starter on the 84 and 85's when they have a higher CR then the I engines.

[DaN]

Sweet thanks.
The starter seems up to the task. It actually starts faster now without the gear reduction, I'm assuming.

What is the purpose of the unloader relay?
Does it cut all other power robbing functions while cranking?

The terminal for the black and yellow wire is grounded at all times, except when cranking? it's ok to have power on that wire while cranking?

I'm just trying to understand this circuit.
Thanks guys

[James Crivellone]

I use an ETA Starter on my I engine without issue lol.

Although it cranks a tad slower.

[rs4pro3]

Does it cut all other power robbing functions while cranking?

Ding !
Yep it cuts power to the Windows and what not while cranking, it does this by backfeeding voltage up that wire to the relay which turns it off, then once your done cranking it gets grounded and those functions work.

[DaN]

Word, that worked nicely. I hooked both small wires on the same terminal. Problem solved.
Thanks

[Jarvis]

Higher compression requires stronger starter.

Well an 87 325e is 9.0:1 and a 90 325i is 8.8:1...

But I know what you mean. But there must be some other explanation for the e -> i starter differences.

[DaN]

That sucks, why did they drop the compression?