My top motor decided to quit late last fall and left me with a blown 40 amp fuse and quarter windows stuck down after manually closing the top. I jumpered the window relays to get the car set for winter driving.

Anyway, I finally got through enough other projects to take a look at the motor and found the problem I'd hoped to find. With the help of Dennis07's post on motor troubleshooting https://www.jaguarforums.com/forum/x...or-how-137620/
and reading about Autobahn kid's experience with the same symptom https://www.jaguarforums.com/forum/x...lowing-136196/ I worked my way through the issue. Gotta love this forum!

When I saw that one of Autobahn kid's pictures showed a tranzorb between the power input wires, I hoped that was my problem. They are pretty trustworthy, but I've had a couple memorable problems at work when they fail shorted.

So, I removed the motor, checked it using Dennis' post, and found the armature to be in fine shape. So far, so good, looking like a shorted tranzorb. I made a minor effort to unsolder it and saw it would make an ugly mess. I then pressed the armature bearing out of the case and removed the suspect part. Sure enough, it is a dead short. New part is on order from Newark Electronics for 29 cents. I'm going to move it to the connector, though. I put the whole thing back together without the offending part and the motor works great.

Now, a little more on the bearing installation. I simply pressed the shaft and the bearing came out of the endplate. My apologies for not taking pictures, but Autobahn kid's post shows some of it. To properly take this end of the motor apart, one should remove the externally toothed retainer, the oil seal, and a circlip you can't see until the seal is out. The shaft would then easily press out of the bearing. This, of course, might trash the seal which wouldn't be very good news. On the inside, the bearing is retained by a toothed retainer just like the one that holds the seal. So, when I used my Bubba method to disassemble it, the washer tried to do its job and made some gouges in the housing. It all went back together just fine since I clocked the retainer to the non-gouged areas. If I did it over, I'd try to pull the seal, but wouldn't worry too much if I had to press it apart the same way in lieu of ruining the seal.

I hope someone else can save some time, money, and effort from my experience with this.

Mike

 

Nice job, Stratohammer! If I might add a little commentary ...

The tranzorb that Stratohammer refers to is the little tubular bit that I described as a noise suppression device. An observed short in the motor can be unambiguously traced to the tranzorb only after the armature has been isolated from the brushes (see pics in the link in my sig. line below.)

Getting at a failed tranzorb to replace it without further dis-assembly of the motor ... not so easy. Stratohammer went where I lack the skills and tools to go, and pressed the armature out of the casing (that holds the brush assemblies) after which the tranzorb will be easy to get to.

Another option, for people like me, might be to leave the armature in place and snip or unsolder one of a failed tranzorb's wires so as to get it out of the circuit. A replacement tranzorb can be inserted across the black and white power wires, external to the motor, as Stratohammer said.

 

Any speculation on what causes these motors to fail internally? With the hydraulic hoses, we know it's inferior material quality. So what's causing these shorts?

 

Speculation:

As with the hoses, heat may be the dominant factor. The tranzorb is called on to absorb a lot of energy to suppress motor transients. The motor is designed for low duty cycle, and is completely unvented. Could get a little toasty in there, especially with repeated raise/lower top cycles.

Maybe.

 

If the vehicle ever had voltage regulator issues, or the top was operated while on a battery charger, that also could have over-stressed the part and planted the seeds of early failure.

 

I am not sure if this has already been done but is there an easy-to-follow DIY (preferably with pics) for addressing the motor issues? If there is not already one in the FAQ section it would be useful.

Doug

 

Dennis07 - I agree that the offending part could have been removed with a small pair of wire cutters. It certainly would have saved some time and effort. My inner monkey just had to explore uncharted territory!

I've got to say that I was quite impressed with the quality of the motor. It isn't set up for continuous duty, but that's in line with its intended function.

WhiteXKR - I agree. I'm the second owner and this was obviously someone's summer/Florida car as evidenced by PO addresses and the installation of a battery cutoff switch.

Mike