Lotus Elan

S4 Window Troubles

PostPost by: elanern » Sat Sep 25, 2010 3:32 am

All,

I need to tap into your infinite wisdom, please.

The car is a 1970 Elan S4 Federal DHC. I've been reassembling the doors after having removed and cleaned up the door hinge pins so that door adjustment would be easier. I cleaned up the window frames, lubed the pulleys, and installed new window "fuzzies". I used new clips to retain the door latch and lock rods. I cleaned up the lock assemblies and got the doors adjusted fairly well (bottom rear corners of both are typically sticking out). So, the windows are installed, doors are adjusted, and the inner and outer handles/lock mechanisms work as designed.

The windows, in their frames, on the bench and in the car, without the motors installed, move up and down with no binding or other issues. But there are issues with the motors installed:

The passenger window goes down with no issues, but is very sluggish going up, requiring a helping hand. The motor seemed to work fine in both directions while bench testing. I tried some silicone spray but ran out, and will pick some up and try it again tomorrow. But the little I was able to spray on the window channels did not seem to help much. Any ideas on why the motor works fine going down but not so well going up?

The driver window goes up and down fine, but the switch is reversed, i.e., you have to push up for the window to go down, and down for the window to go up. Switching the wires on the motor did not change anything. The passenger side window switch works as designed. Any ideas on what could cause the switch to work in reverse?

Thanks in advance.
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PostPost by: 69S4 » Sat Sep 25, 2010 9:11 am

elanern wrote:The passenger window goes down with no issues, but is very sluggish going up, requiring a helping hand. The motor seemed to work fine in both directions while bench testing. I tried some silicone spray but ran out, and will pick some up and try it again tomorrow. But the little I was able to spray on the window channels did not seem to help much. Any ideas on why the motor works fine going down but not so well going up?


Gravity assist usually helps when the window is going down! Mine are def slower going up but not far off the rate of our modern cars.

I've had two probs in the past that have reduced the "up" rate - firstly, the usual dodgy wiring connections - earth and feed. It should be simple enough to check that by running some temp bypass wires. Your switch problem suggests all isn't as it should be there. Secondly, internal problems in the motor - brushes, magnets coming loose etc. Have you stripped the motor down and had a look? Replacing the channel felt that the window runs in def slowed everything down when I last did it but not that much and it seemed to recover ok after a bit of settlement time.
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PostPost by: oldelanman » Sun Sep 26, 2010 7:41 am

The passenger window goes down with no issues, but is very sluggish going up, requiring a helping hand.


It could be that the cable is too slack which will cause the glass to tilt and jam in the runners as it lifts. When you tested it on the bench did you lift the glass by hand or by turning the drive spool ? Or it could be that the glass is not clamped squarely on the cable - when you assemble it, tension the cable and clamp the two free ends in the front clamp stud then lift the glass to the top of the frame to square it up before finally tightening the other clamp stud.

The driver window goes up and down fine, but the switch is reversed, i.e., you have to push up for the window to go down, and down for the window to go up. Switching the wires on the motor did not change anything.


I don't understand how this can be. I'm no electrician but it seems to me that if the window goes up and down then the polarity of the wires at the motor must be being reversed by the switch as it should be so swapping the wires at the motor must reverse the operation of the switch. Or am I missing something here.

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PostPost by: paddy » Sun Sep 26, 2010 10:22 am

oldelanman wrote:I don't understand how this can be. I'm no electrician but it seems to me that if the window goes up and down then the polarity of the wires at the motor must be being reversed by the switch as it should be so swapping the wires at the motor must reverse the operation of the switch. Or am I missing something here.


When a motor has a permanent field magnet, then this is true; reversing the current through the (reactive) coil will reverse the direction of the force. However, when the motor as an electromagnetic field magnet, then simply reversing the polarity changes both the direction of the magnetic field and the current, so there is no net change in the force.

The way the switch is wired it doesn't simply change the polarity of the supply to the motor; it supplies power to a different terminal on the motor, which is wired internally to energise the coils in a the opposite direction relative to one another. The motor therefore has one earth connection and two alternative positive connections (one for up and one for down). Reversing these two connections should have the effect you want.

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PostPost by: oldelanman » Sun Sep 26, 2010 11:59 am

paddy wrote:The way the switch is wired it doesn't simply change the polarity of the supply to the motor; it supplies power to a different terminal on the motor, which is wired internally to energise the coils in a the opposite direction relative to one another. The motor therefore has one earth connection and two alternative positive connections (one for up and one for down). Reversing these two connections should have the effect you want.


That's not how I understand it.
The motor is actually a standard ford windscreen wiper motor which normally only runs in one direction. It has one supply wire connected to one of the carbon brushes and two earth connections - one connected directly to the other brush and a second also connected to the second brush but via slip ring in the gearbox to achieve the self park function as a wiper motor. Thus the motor would be supplied through one wire and earthed either via the wiper switch or, when switched off, via the slip ring until the park position is reached.

In this application the second earth wire is redundant and is not actually connected to the slip ring (see pic below) the supply and earth connections are both made through the window switch itself. The switch is double pole double throw with bridge wires on the back to achieve reversal of the supply and earth connections. If the system worked as you say the switch would only need to be single pole and would not need to be earthed.

There is an earth spade connector on the gearbox cover screw but this serves only to earth the case and is not connected to the motor itself. I can only assume it's there for radio suppression.



Regards,
Attachments
Window motor 001.jpg and
Window motor 002.jpg and
Window motor 003.jpg and
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PostPost by: summerinmaine » Sun Sep 26, 2010 5:14 pm

This and the fixed window frames makes me glad I have the old reliable sliding windows.
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Left Window.jpg and
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PostPost by: FOX5D » Mon Oct 04, 2010 8:14 pm

Changing the window felt to the early +2 one will reduce the resistance when the glass is going up. Roy, the parts guru at Paul Mattys suggested this to me when I had a motor that kept stopping when going up. I took his advice and it fixed the problem straight away. He supplied the 2 metre length for a very chaep price.

I also had a switch that had bee wired up the wrong way round, so I just switched the leads on the motor and the problem was solved. I learnt this from a previous thread.

It is a Ford motor 9part no. (1AB 17B571) and you don't need to wire up the black cable.

Hope you find this helpful

Cheers

Jim
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PostPost by: billwill » Mon Oct 04, 2010 10:25 pm

>you don't need to wire up the black cable.


The black lead is for earthing the metalwork of the motor and in theory should cut down any radio interference caused by the motor.

As you say it is not needed to make the motor rotate either way.
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PostPost by: elanern » Sun Oct 17, 2010 7:56 pm

Well, I pulled the passenger (right) side window assembly out to see if there was a cable issue as suggested by oldelanman. Sure enough, the cable has lots of slack. Looking more closely at it, the cable must have been replaced at some point in the past - there is no adjustment possible, the cable ends were joined in the window driving pulley! There is no way to adjust it, so, the hunt begins for a new cable. I'm guessing that the window had been replaced (no manufacturer marking like the driver (left) side) and whoever did the work found it easier (??) to redo the cable the wrong way.

I still have not looked into the wiring issue on the driver window. I will take out the dash (again, sigh) and check out the wiring at the switch. I'll keep you all apprised of what I find out.

What I am learning with this rehab project is assume the previous owner(s) or their mechanics did not know what they were doing when working on the car. There have been so many things not right that I should have just completely disassembled it and started from scratch. :?
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