Window lift motor replacement?

[Kevin H]

Originally Posted by Sam410

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.

That Heath Robinson mechanism is amazing - makes the system on the 411 look so elegant!

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.

Originally Posted by Sam410

Might be simpler than finding new micro switches?

Definitely the way to go IMHO
here's a few 21A micro switches at RS Components

[penman]

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.

[geo]

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

[Kevin H]

Originally Posted by geo

...mine benefitted from spraying a silicone lubricant on to the guides in the door frame where the edges of the glass contact.

I lubricated the guides on my 411 with silicone but it didn't make any difference.

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.

Originally Posted by geo

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.

Yes, that long worm-gear-in-a-tube mechanism has a lot to do.

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.

[412usa]

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

[MYTA21]

With the aid of the photos of the
Piper lift motors, l have been able to sort out the problems.
From those, I could see what the whole thing looked like.
The reason the window would not open from a fully closed postion was that the cam attached to the chain went past the limit switch, so by adjusting the clearance, I appear to have solved that! A screaming noise that I thought might have been related to the spring assistor turned out to be due to the manual winder bevel gear just brushing the motor bevel gear. Resolved by new spring, so as to give it clearance. Thanks for the help.