| Author | Message | ||
     Mick Matheson Yet to post message Username: mickmatheson Post Number: 1 Registered: 08-2021 |
Before I delve too deeply into something I shouldn't, can anyone let me know if I'm on the right track in diagnosing a window that won't go up or down. It's a Shadow 1 (CRH7765) with Piper window motor, passenger's door. I can hear the solenoid clicking when I activate the switches, both up and down, but there's no motion. The motor is not driving (chain tension doesn't alter at all). The chain is good (removed, checked and lubed). The glass slides freely (disconnected and checked). I cannot turn the emergency window winder shaft at all, nor can I turn the chain-drive gear by hand. Is there anything I should check before accepting the possibility the motor is the problem? If the motor is the problem, I'll have more questions... | ||
| Omar M. Shams Grand Master Username: omar Post Number: 2157 Registered: 04-2009 |
what happens when you disconnect the motor and give it a direct 12v supply? does the window go up and down then? | ||
| Alan Dibley Frequent User Username: alsdibley Post Number: 301 Registered: 10-2009 |
These motors suffer from water damage. Although they are wrapped in a rubber coat corrosion sets in (50+ years) and either damages the field windings (green crud) or fills the armature/field-pole gap with rust. If water does get in the rubber coat keeps it there. The field windings are easily replaced if you know how, but if the armature is rusted stationary or the armature windings are corroded the motor is useless. It is unlikely to have worn brushes - the usage is a few minutes/year but, because one side of the supply is permanently connected, corroded brush wires and/or holders seizing the brushes is likely. Either way you are going to remove the motor, so do it and cut the rubber coat off to see. How do I know all this???? Rebuilt ones are available from UK suppliers, for the price of a cheap second-hand car. Consider that a second-hand motor may be close to failure - unless you can inspect the innards before purchase. Alan D. | ||
| Mick Matheson New User Username: mickmatheson Post Number: 4 Registered: 08-2021 |
Omar, unless I picked the wrong wires, connecting 12v directly to the motor does nothing. Not a good sign. | ||
| Mick Matheson New User Username: mickmatheson Post Number: 5 Registered: 08-2021 |
Alan, thanks. Looks like water hasn't been a problem but I do suspect the internals are seized. I'm just hoping there are some other options before pulling it apart. By the way, when you mention rubber, that doesn't quite match with what I'm looking at here. The Piper motor appears to be encased in plastic. The windings under the cap on the rear (the one held on by the retaining clip) look pristine, as if they were renewed recently. | ||
| Omar M. Shams Grand Master Username: omar Post Number: 2158 Registered: 04-2009 |
Dear Mick, If any motor does not respond to a source of electrical power regardless of the application - then the path is clear - the motor is toast. | ||
| Jeff Young Frequent User Username: jeyjey Post Number: 447 Registered: 10-2010 |
The window motor brakes are only on Shadow IIs, right? | ||
| Robert J. Sprauer Frequent User Username: wraithman Post Number: 695 Registered: 11-2017 |
The parts manual on the Bentley Heritage site will confirm your question. They are on the early cars as well | ||
| Alan Dibley Frequent User Username: alsdibley Post Number: 303 Registered: 10-2009 |
I've just realised that my post was about the oblong-type-motor. If it is not a squarish black shape with four coloured plastic wires then ignore my post. If not, not. But lots of what I said is still true. Alan D. | ||
| Mick Matheson New User Username: mickmatheson Post Number: 7 Registered: 08-2021 |
Alan, I think we are talking about the same motor. | ||
| Alan Dibley Frequent User Username: alsdibley Post Number: 305 Registered: 10-2009 |
" The windings under the cap on the rear (the one held on by the retaining clip) look pristine, as if they were renewed recently." This is the brake, which stops the motor free-wheeling when un-powered. If that is not energised the motor appears to be locked. Does that affect your diagnosis? Incidentally this is not a "normal" DC motor. It needs the following to operate:- 1. 12volts applied to the yellow wire which is the common of the armature (via a brush), the two field windings, and the brake solenoid - this last is an external connection via the tab-strip. This has permanent 12volts via a fuse, which is why any moisture soon causes corrosion. 2. 0volts applied to the yellow/black wire which is the other side of the armature and ONE of the two field windings - red or green (swap the field winding to reverse direction). In normal operation the armature connection is supplied by via a relay contact, the field by the operators switch. I don't have access to a motor without dismantling my car, so I have worked out the colours from the wiring diagrams, which is not as simple as it could be. These motors take a lot of current and have high torque but low speed. Don't get you fingers in the way. HTH Alan D. | ||
| Alan Dibley Frequent User Username: alsdibley Post Number: 306 Registered: 10-2009 |
I've just found a carcase of part of a window motor. The colours in the previous post ARE right. Alan D. | ||
| John Kilkenny Frequent User Username: john_kilkenny Post Number: 338 Registered: 06-2005 |
Alan's wiring information is for the standard Silver Shadow. I believe the MPW is somewhat different, along the lines of the attached diagram.  | ||
| Alan Dibley Frequent User Username: alsdibley Post Number: 307 Registered: 10-2009 |
John, you are right - I have not seen such a motor before. Something new every day. The motor operation is the same - two independent field windings plus a normal armature - but the implementation is different. The wire colours are different. The armature polarity is reversed to reverse the motor, so the field windings must both energise in the same sense. The relay system is necessary to accommodate the end-stops and inching complications, I suppose. And there is no brake, so if the motor doesn't go round........ BUT, if the motor has a similar construction to the "standard" motor it suffers from the same failure modes. If not, not - it's got new ones. Alan D. who is searching for more info on "Piper motors". | ||
| Alan Dibley Frequent User Username: alsdibley Post Number: 308 Registered: 10-2009 |
PS. ...and I've discovered that Piper motors are even more expensive than standard ones. Good luck from Alan D. who would have a go at fixing it if it were mine, but.... | ||
| Mick Matheson New User Username: mickmatheson Post Number: 8 Registered: 08-2021 |
Well, the electrics are all fine! Thank you for the wiring diagram and advice, which I have filed away. John, that diagram is gold. I wondered why I couldn't make any sense of the one I was looking at, which must be for a four-door. Anyway, in there meantime, I dismantled the motor and discovered two things. First, the old grease had turned to resin. The minute I had the gearbox apart and applied 12v, the motor span like a top. Beautiful. I thought that may have resolved the issue, but... Second, after cleaning up the old grease, I found a series of stripped teeth on the drive gear. Does anyone know where I might find another? (Yes, I checked FS but, well, let's just say I don't complain too much about parts prices but I have my limits.) I may also need the chain-driving gear that fits on the other end of the shaft, as this one is stuck solid.  | ||
| Jeff Martin Frequent User Username: jeff_r_1 Post Number: 269 Registered: 07-2018 |
What about a jobber (machinist) ? I was going to have a valve timing gear made for my car and the guy thought he was really going to soak me good at 600.00$ Canadian. Later I found some new old stock. I very often find that Introcar and FS outprices themselves on some things. Sometimes one can get one made (or repaired) for much less. Junk yard ??? | ||
| Omar M. Shams Grand Master Username: omar Post Number: 2160 Registered: 04-2009 |
I had a window motor failure on a Ford Thunderbird. Looked the world over for a replacement gear but nobody sells them. It is either the whole mechansim or nothing. I then looked up "window gear" on ebay and many gears came up from many cars. I ended up buying an obscure gear from a vendor in Turkey and it fitted perfectly. sometimes it is worth doing something crazy like this. It cost me $8 but i have a great outcome. Omar | ||
| Mick Matheson New User Username: mickmatheson Post Number: 9 Registered: 08-2021 |
I'll see what I can find and let you know. | ||
| David Gore Moderator Username: david_gore Post Number: 3984 Registered: 04-2003 |
Hi Mick and welcome to our forum, I suggest you contact forum member Kelly Opfar and he may be able to machine a replacement gear for you using your damaged gear as a template. Many of our members here and from our international counterparts will vouch for the quality and reasonable cost of his work. Kelly's username is Kelly_opfar and you can message him direct through this forum using this username alternatively you can contact him through his website: https://www.britishtoolworks.com/  | ||
| Trevor Hodgekinson Frequent User Username: wm20 Post Number: 253 Registered: 11-2006 |
When you get it back, carefully check the braking and stopping mechanism. I had a window fail in one of the wedding cars and just swapped out the entire mechanism from the current rebuild car. I for the life of me could not find a problem with it till like you I found missing teeth. In this case the timing ? of the motor was out and it did not shut off properly when the window was fully raised so the motor was trying to drive the window up two more teeth than the window could travel . We never sorted it out cause Premire Carr killed off the wedding car business and that particular car was sold off to another Shadow 1 owner for spares. | ||
| Jim Walters Frequent User Username: jim_walters Post Number: 344 Registered: 01-2014 |
Let me know the diameter and the number of teeth and I'll go through my parts. I might have one. SRH8505 SRC18015 SRE22493 NAC-05370 www.bristolmotors.com | ||
| Omar M. Shams Grand Master Username: omar Post Number: 2161 Registered: 04-2009 |
I agree with David - Kelly is a fantastic machinist and his work is impeccable. Forget that he is at the other end of the world - post is great from the USA. He has a Shadow of his own and is a Rolls-Royce enthusiast. | ||
| Mick Matheson New User Username: mickmatheson Post Number: 10 Registered: 08-2021 |
Jim, the outer diameter of the gear is approx just under 2" (call it 1 15/16" or just under 50mm) and the gear has 69 teeth. The shaft is 2 9/16" (65mm) long. I think there was a long shaft and a short shaft, and the long one can be cut down if necessary. Not sure which one mine might be. If you happen to find the chain-drive gear (with 5 pairs of well-spaced teeth) that goes onto the other end of the shaft, that would be good too. One tooth on mine is damaged so it wouldn't hurt to replace it. |
