Window relay fix wiring diagram?

Hold on mate Ive just started that job myself on my Testa and Ive got a magazine article with pic, I'll try and scan it and post.

Cheers Si

I see Phils give you one and mine was for Testarossa anyway, silly me

 

This one ?

 

try again...........this one ?
Image Unavailable, Please Login

 

One very minor problem with this design is that the windows are locked when not in use. If you have to use the manual lever for any reason, you must disconnect one of the relays or the window motor at the door harness.

 

Have you got a link to that info. I'd like to understand why that would happen?

 

To be honest, no I did not, the windows did not work at all when I got the car. All they needed was a good clean and they worked fine. Not super fast but ok, I did clean all the switches tho'

 

CAUTION,
Don't do the relay conversion unless you also either perform, or know that your window lift mechanisms have had, Ed Schreyer's Slow Power Window Fix (cleaning/relube service) first.

See: http://70.85.40.84/~ferrari/discus/messages/256120/114996.html

When the lubricant has turned to cosmoline, The high wiring resistance may be all that's keeping the motors from smoking themselves instead of just creeping & stalling.

If the lift service hasn't been performed, the relay conversion's greatly reduced wiring resistance may be able to let enough current flow thru the severely mechanicly overloaded motors to fry them fairly quickly.

 

Thanks for the link. The circuit diagram with the relays looks good. I just don't understand how a motor with ground potential on either side of it will lock up?
The detailed walk through of how to service the mechanism is excellent.

 

The significant part of the lock-up is that the motor's winding connections are shorted together. Any attempt to mechanicly rotate the motor turns it into a generator with a short across it's output. It's probably not impossible to turn the motor, but the faster it turns, the more force it will take.

 

The motor may be "locked" up by this mod, but you can still use the manual crank. When you use the manual crank, you push in on the crank and it disengages the gears between the motor and the spool. If you look at the way the gears are meshed you well see that there is no way you could turn the mechanism if they stayed meshed because the motor has a worm gear on it. It can only be "driven" from the motor side and not the other way around.

Birdman

 

Having never used the crank, I didn't know this. Oh well, I've only had the car 18 years!!

Regarding the locking, the reason is as stated above, is that a DC Motor is also a DC Generator. By shorting the leads, you end up putting an near-infinite load on the genarator (mathematically speaking). Driving an infinite load requires infinite force. I tried it once with a small DC motor, albout half the size of the 308 window motor, and you could not do *anything* to turn the motor. It was amazing.

 

That DC motor thing is a WAY COOL example of physics!!

Someplace I have some pictures of the guts of the window cable gear thingy and I'll post them to illustrate a bit better.

I couldn't figure out for the longest time why the darned manual crank wouldn't work. When I opened up the door to clean and re-lube the thing, then I looked at it and realized how it worked. You have to push the crank in really hard to disengage the gears and be able to turn it.

Birdman

 

If you have a free spinning armature in a motor/generator and short circuit the commutator it isn't going to stop you from turning it. I understand the practice of motor becoming a generator but where is the initial V+I potential coming from to stall it? You have to be spinning it at a high rate of knots to generate anything in the first place and then all you would do is growl the armature.
You're talking about a perpetual motion machine. I'll buy as many as you can sell me!

 

I also find this hard to believe, I'd be surprised if you could feel the difference.
Shorting across the 2 terminals is how the "brakes" work on a slotcar (it certianly does not lock the rear wheels on a slotcar)

 

Here is a shot of the inside of the gear/cable pulley assembly. You can see that the motor has a worm gear and drives the gear around the outside of the cable pulley. When you turn the pulley directly with the hand crank, you push in hard and it disengages the pulley gear from the worm gear. (In this photo, the handle would be pushed in from the other side, pushing the pulley towards you). Without this disengagement, there is no way you could turn anything because of the worm gear.

Birdman
Image Unavailable, Please Login

 

Thanks for the pic Birdman. Looks like there's just a large belleville washer that holds the gear engaged?
I agree you'll never be able to turn the gear expecting the armature to rotate. One of the reason worm drives are used in electric windows is so they can't be forced down.

 

Is that what they call that?? I knew it must have a name. Yeah, a washer that is "wavy" and it compresses when you put enough force on it. Pretty simple but it works well.

Birdman

 

As the motor turns, the armature moves through the field of the permanent magnets inducing a voltage in the armature's coiled wiring. Since the wires are shorted, the energy goes back into the system and creates it's own magnetic field that is the inverse of the field of the permanent magnets, causing the magnets to be attracted to the armature. The efficiency of the motor, and the configuration make large differences in the braking effect. I'm not much of a DC motor guy, but that's my understanding.

I've designed control electronics that move DC motors (gear head motors to be exact) back and forth using an H-bridge MOSFET driver. When not in motion, the circuit would make the H-bridge short the terminals, effectively locking the motors in place. On the gear motors we were using (the motor part was about 1/2 - 2/3 the size of the 308 window motor), you could not even budge the motor in either direction with a one foot long wrench on the drive shaft.

That being said, I doubt the 308 window motors are "high-efficiency" in any way and the braking effect might be very weak, but I still bet it would fight you enough to be anoying if you were trying to raise or lower the window. Of course, now knowing that you can disengage the motor from the winder, it's a really a non-issue anyway.