Window Motors - Travel Limit Switches

Last year I had disassembled the window motors in my 85 308 GTS to remove the cement-grease which was causing them to operate. Since refreshing the grease and cleaning the motor's brushes, they operate very reliably and quickly but a new problem has cropped up that I cannot find any discussion about. Normally, one pushes the up or down side of the button and the window moves in the appropriate direction until it arrives there. Once it is fully opened or closed, even though the button is still pressed, the window stops moving. Something I have never given much thought to.

Well, on my car's driver's side only, when the window reaches full-open or full-closed the motor does not stop. Because it has so much torque now, it makes an awful grinding noise which appears to be the finger-gear that is directly connected to the motors shaft jumping out of the rubber joint that connects to the gearbox. My question is this..... Does anyone know what
"stops" the motor when it reaches full-open or full-closed? Is there a limiting device in the circuit which only allows so much current ot flow through the motor, and 'cuts" the voltage when too much flows (like the motor reaching full-open or closed). Or is there a mechanical limit that cuts the circuit when the pulley reaches a certain positon? Any help would be appreciated.

 

It is a part of the motor assembly and oft called a 'stall breaker'. After I added relays to remove the voltage drop in the window wiring, I became worried about the brutal force on the cable, especially when lowering. When the window hits the thin rubber lower stops, the cable must transmit the extra force to the motor where the stall current triggers the circuit to open. Incidently, the fuses are required to withstand 110% of rated voltage forever but blow beyond...the 'stall breaker' must open before the fuse blows even though the stall current may be 300% of normal.

I added a mechanical limit switch at the bottom on a homemade bracket to remove the motor voltage just before the window hits the rubber stops. Used a leaf type microswitch, easily adjustable, removing voltage to the relay coil. No more grinding halts, sounds sophisicated and I no longer worry about the cable or paper thin rubber stops.


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Ferrari 308 Wiring Diagrams
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The exact thing happened to me when I replaced my drivers side motor.It has so much torque that when it reaches the closed position I too have this grinding noise.I have been thinking to do what Paul did but just another one of those "I haven't got around to doing it yet"

 

This is the movie of my window in action. It is presently resides on the Ferrari forum at Yahoo groups. Being 1M in size, it exceeds the 480k limit of this forum. Best viewed with MS Media Player in Repeat mode. I have no way of knowing whether it will play for someone not logged or otherwise authorized at Yahoo. So you might have to join the FerrariTech group to see it. Appreciate if someone could test this let me know.

Listen to the difference on the downward direction stop...you hear only the relay click. Whereas the upward direction still has the clunk against the rubber stops. Now when I look at it, I am embarrassed that I didn't clean things up before starting the camera...but I was too excited about the performance to wait. Sorry I don't have pix of the limit switch. It is mounted to an 'L' bracket attached to the inner panel of the door at the left opening where the relays also reside.

http://f1.grp.yahoofs.com/v1/gNPcRwe31wu9Ntq3CyH-8j8SOjC3SEs2OUds-dQNrnx46BA3_mhO4U90syptFtqmVcqTdMHgDLGnfZT3RxdP6gQiLW_JxzbnLDAxyjQ/Windo.wmv

 

Paul, that is great that you were able to arrive at a workable solution by adding switches to solve the problem, and I always take my hat off to ingenuity. However, I prefer to take the route of repairing the stock "stall breaker" sytem that is supposed ot provide this function and was hoping that somoene elese had already been there & done that. Any info would be appreciated before I jump blindly into reverse engineering the system. Thanks.

 

Kevin, I do hope you report what you learn about the current limiting which stops window travel at full up and down position.

With my newfound window motor speed from the relay mod, I do experience occasional fuse blowing with fast acting ATO/ATC fuses and I have been unable to find slo-blo or medium lag fuses in this format. The seemingly endless variety of AGC fuses is a definite advantage for those who use the Birdman type blocks.

Because of stall and inductive spike conditions, motor circuit protection really should not utilize fast acting fuses as one tends to over spec amperage to compensate rather than tailor the fuse blow time, a poor engineering practice. So, I have ATO/ATC self-reseting circuit breakers on order and will report results when I have them. Breakers are either heat or magnetically tripped and no specs were available (feel like I'm doing a 'dear diary' here) so experiment it is.

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308 Wiring Diagrams
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