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8 & 10 cyl Bristol cars Type 407 onwards - restoration, repair, maintenance etc |
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I spoke to Bentley specialist Introcar when looking for new microswitches (which they couldn't supply), who said they tend to junk the Piper system and fit more modern motors when they have to fix them. Might be worth trying them for suggestions? |
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George |
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Window lift motor replacement?
Hi all -
"The other problem on the 412 was that even the later type of motor got very wet and many of the connections suffered corrosion. After rectifying this along the same lines as the switches, I glued builders polythene inside the door to stop any water landing on the motors." Don't know if this applies, but an expert on Imperial (Mopar) window motors found that the window motors were corroding internally because the hot motors drew in moisture when cooling, which collected on the bottom of the casing and could not escape. Fortunately, these same motors were used in nearly all Mopars for about 20 years, so easily sourced. There is also an Imperial owner who offers a service to rebuild window switches. Bob |
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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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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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Kevin |
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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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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. Definitely the way to go IMHO here's a few 21A micro switches at RS Components |
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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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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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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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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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409 Window lift motors
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. |
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Hello Kevin,
Has anyone come up with a solution for the replacement of the Piper mechanisms. My micro switches have broken up and I bought two second hand complete units from Bristol Services, but these are not up to much |
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Hi Mike,
I haven't heard of any replacement. Mine do still work, albeit slowly. I improved their performance by renewing all the wiring and connectors. However, if it's only the micro switches that are kaput, then I wouldn't think it would be too hard to adapt some modern micro switches to serve the same function. It would just be a matter of changing (re-fabricating) the mounting arrangement for the switches. |
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My "Series 6" 410 has a modern window lift mechanism that Bristol sourced from a U.S. company called Speciality Power Windows. It's very effective and look well built. Bristol also sourced a wiper motor mechanism from them for the series 6 that they adapted with a custom wheel.
Here's a picture of the power windows mechanism (I dont understand why the picture is upside down). The switches are standard, although Bristol added a small electronic module allowing for auto up and down. |
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motor, window |
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