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| 8 & 10 cyl Bristol cars Type 407 onwards - restoration, repair, maintenance etc |
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08-07-09, 11:12 PM
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Window lift motors
Trsut my car, a 409, to have the odd ball units, ie the Piper motors! However that might mean some input from some RR contacts. These are chain driven- noisy. ( Sounds like a port cullis raising!)
Raising the glass is assisted by some coiled spring devices which resemble steel tape measures. I have not taken anything apart yet, but the problem seems to be that on one window, the motor raises the galss to it closed position. For a couple of times, it will work up and down, never failing in an intermediate position. Then on closing, it fails to reopen-a click is heard. Wind the screwdriver in the hole and it will work for a while. So, am I correct in thinking this looks like limit switch? 
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09-07-09, 05:09 AM
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Quote:
Kevin
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09-07-09, 05:13 AM
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Pictures inside 411 door
As mentioned before, attached are the pics of my window lift mechanism and motor. The red arrow points to the "screw tube"
Last edited by Kevin H; 10-07-09 at 01:35 PM.
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09-07-09, 05:06 AM
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Quote:
The 411 uses a screw inside a tube with a slot down one side. There's a bracket fixed to the screw which in turn is connected to the bottom of the window. (I'll post some pictures later from a different PC.) I'm sure it's not helped by the fact that the tube which carries screw is vertical but the motor is mounted horizontally, so the screw/tube has to bend through 90 degrees! But maybe they do that to stop water running down the tube into the motor! Quote:
The limit switches on my 411 are fine, the problem is the motors operate very very slowly, but they're not noisy.
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10-07-09, 09:55 AM
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Incidentally, I think these windows are unusual in having a limit switch at the top of their travel. Most windows do not have this, as can be determined by the slight dimming of headlights if you try to close the windows when they are already closed (at least on many modern cars I've tried.) As the problem on your 409 seems to be at the top, it would probably be possible to bypass the limit switch altogether, as the window frame will obviously stop the window going too far. Might be simpler than finding new microswitches?
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10-07-09, 02:00 PM
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On proper modern cars they usually use control circuitry to monitor speed of the motor and/or the power exerted by the motor (current drawn) and will stop the motor if it slows down too much or uses too much power. I don't know how the 409 is wired, but on my 411 the windows were wired directly to the battery, not even on the ignition acc circuit. Nor were there any fuses or relays in the window motor wiring, so I wouldn't recommend removing the limit switch. Quote:
 here's a few 21A micro switches at RS Components
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10-07-09, 08:25 PM
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Hi
I think a lot of manufacturers originally wired them direct so that windows could be opened/closed while parked up. There were then a number of accidents where kiddies left in vehicles, who stuck there heads out of the open window, knelt on the up switch and throttled themselves. Putting it on, a first key click accessory circuit or even the ignition on circuit removed/reduced that risk.
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11-07-09, 01:09 PM
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I do not know how true this is of the Bristol implementation of electric windows (although I did it on mine), but on other cars, reducing the amount of effort on the electrics to raise and lower them makes them work better. In addition to keeping the outside of the window glass clean, mine benefitted from spraying a silicone lubricant on to the guides in the door frame where the edges of the glass contact.
After all, just think of the amount of effort required to lift a window with a non-assisted window winder, it is asking a lot of that relatively small motor. George
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12-07-09, 05:18 AM
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Quote:
In an attempt to determine what the problem was I played around with the alignment of the window frame and did manage to get the windows working at an acceptable speed. Unfortunately however, when the window frames are aligned so that they seal with the opening in the car body, the windows once again move very slowly. Clearly more power is needed from the motor to overcome the resistance of the frame/guides. Quote:
Modern cars tend to use a gear reduction system acting on a scissor type lever mechanism, which makes much lighter work of moving the window. So the motors are smaller, yet they are able to exert considerable force on the window. As for the wiring of electric windows directly to the battery, this has been responsible for the deaths of many children over the years. The first one being recorded in 1962. I've been trying remember when wiring them to the accessory circuit (requiring the ignition key) became routine in the British auto industry. I think it was happening by the mid 1970s.
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12-07-09, 06:00 PM
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Window lift motor replacement?
Kevin,
From memory, the window lift on the 412 is very different. It is not a chain drive but a scissor type action. As others have mentioned the 412 switches have problems as all the current runs through them. I had an electrical engineer friend design a relayed system but in the end did not install it as the auto electrician who had the motors rewound said that the system was fine as it was, if well lubricated. Peter
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| motor, window |
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