My BMW journey has begun

Be thankful that you're going from 2-wire motors to 2-wire motors. 3-wire to 2-wire was a pain especially by the time the relays got added in. You ARE adding in relays though, correct? :)
 
D Calkins said:
Because I have the circuit breakers under the steering column I didn't believe it was necessary.
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They would be serving a different purpose. At least in my car, the wiring originally went through a very long route from battery/harness into fusebox area then out to console switch then back towards front of car before then heading rearward to the window motor. Closing the switch (up/down) allows the electrical signal to go that whole route and power the motor, but because of the long run the actual voltage delivered at the motor is less than what is coming out of the battery (your 12-13V). There's a long thread on this where someone (perhaps Scott) calculated the actual voltage drop and it's significant, which means less power to power an old motor with some resistance from grease, etc. Updating the motors and cleaning the track helps, but the relay allows a run directly from battery straight back to the motor - the shortest possible route. The switch in the console wires into the relay and essentially controls the gate within the relay either allowing power through or not. That wire run between switch and relay (both there and back) is what is electrically cut out of the original distance that had to be traversed between power to the motor so much less voltage drop. When I first had to deal with this I found these somewhat confusing but after you sit with it for a bit and study the diagrams it makes sense and they are pretty easy to wire in, especially since there is room there in the window area to actually hold the relay next to the motor.
 
This is just my opinion as I have converted two coupes from two wire to two wire e28 motors, the relay is not needed for these and the circuit breakers add another level of complexity.
 
D Calkins said:
My car was just delivered and so far, I'm pleasantly surprised. Can someone please tell me what these wires are from? Would photo # 3 suggest I have a relatively new OE Radiator?

Thanks

David
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74's had a torch in the glove box. Those wires might be for that. Any current in them ?
 
Does this fit look correct?
 

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e9Leveque said:
They would be serving a different purpose. At least in my car, the wiring originally went through a very long route from battery/harness into fusebox area then out to console switch then back towards front of car before then heading rearward to the window motor. Closing the switch (up/down) allows the electrical signal to go that whole route and power the motor, but because of the long run the actual voltage delivered at the motor is less than what is coming out of the battery (your 12-13V). There's a long thread on this where someone (perhaps Scott) calculated the actual voltage drop and it's significant, which means less power to power an old motor with some resistance from grease, etc. Updating the motors and cleaning the track helps, but the relay allows a run directly from battery straight back to the motor - the shortest possible route. The switch in the console wires into the relay and essentially controls the gate within the relay either allowing power through or not. That wire run between switch and relay (both there and back) is what is electrically cut out of the original distance that had to be traversed between power to the motor so much less voltage drop. When I first had to deal with this I found these somewhat confusing but after you sit with it for a bit and study the diagrams it makes sense and they are pretty easy to wire in, especially since there is room there in the window area to actually hold the relay next to the motor.
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The other issue with running the power through the window switches is that those switches are pretty flimsy, and the motors draw a lot of current. The switch itself will age as the contacts burn and corrode, and that will add further resistance.

For those who may not be fully versed in electrical stuff, Ohm's law states that

V=IR

V is voltage, I is current and R is resistance. There are a number of ways to look at the window circuit, but the simple answer here is that the entire circuit from the battery, through the fuse box, possibly though circuit breakers, down about 10 feet of wire to and from the switch, the switch, and then the motor all comprise resistive elements. The motor resistance doesn't change (much) over time. Since V is fixed (V=12v) then IR must be fixed, and if R goes up I must go down...

Ultimately it is the current that does the work in a motor, and because power varies as the SQUARE of current, as current goes down, power goes down somewhat faster...

The entire circuit was not a great design to start with, but over time as the switches age, and the window tracks get gummed up, it gets worse..

Here is the window motor thread at the place where the two-wire relay diagram is discussed:

Window Relays
 
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I have all these loose wires. Most of them are not attached to anything except for some relays mounted to the top of the brake booster and to the bottom of one of the carbs. Any ideas? Does anyone make a color wiring diagram?

Thanks

David
 

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Looks like you have Webers now. These were for the water chokes on a Zenith carb, there was a relay on top booster too, all can be removed.
 
D Calkins said:
Why would someone go to the trouble to tape off all the ends instead of simply removing the wiring harness?
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Probably so they could go back if they wanted. I woudl just put shrink wrap onthe connectors and tuck them away as invisibly as possible. Putting them back would be a huge amount of work if you ever needed or anted to do that.
 
Thanks nicely done. I may need another diagram on the wall.
 
D Calkins said:
Why would someone go to the trouble to tape off all the ends instead of simply removing the wiring harness?
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they didn't want to undo the harness to get to where the wires started. i removed some green / white wires that went to speed relays for carbs a few weeks ago on my car and it hadn't had carbs in 20+ years. those wires went all the way to the fusebox.
 
I know that many have said that Prospero’s diagrams have some slight inaccuracies, but I do find them VERY helpful for a quick and dirty oversight trying to trace wires from point a to point b. I tucked one under my trunk carpet so I have it in case I have an electrical problem out on the road…
 
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