MN12 Thunderbird, Cougar and MKVIII power seat issues...

phils89sc

SCCoA Member
Since I bought my 15K mile LX last year, the power seats on both sides, primarily front to back, barely work. The only way to get the front to back to work, and that only happens when you have the seat height almost all the way up, is to get the height right, then it will move forward and backwards, that is until it gets to a point, then it grinds to a halt. If you wait a minute or so and try again, it will move a bit, rinse and repeat. The passenger side does the same thing.

So, today I decided to see what I could do. I took out both seats and started with the driver side. I flipped it over and proceeded to take the motors out. When I did this, what immediately jumped out at me was the condition of the rotors (commutator) where the brushes make contact..Looks very nasty, like grease or something got into it.

IMG_0042a.jpg

So I cleaned all three of them up and used very fine (400 grit) sand paper to freshen up the surface.

IMG_0044.jpg

I also found that same goop on the brushes

IMG_0040.jpg

I cleaned up the brushes as well, which really didn't look too bad.. Here is the after pic..

IMG_0046.jpg

So, after all of this, and lubing the tracks, front to back, the problem was only marginally better, and by that, I mean barely. I thought I would have better luck on the passenger side, so I took it all apart, to find it a lot cleaner, no grease buildup or anything. The rotor surfaces (commutator) where the brushes touch were not as bad as the other, but still had some buildup.

I cleaned all of this up, but during reassembly, I dropped the brush holder and one of the stupid bushings escaped. I think I heard it actually say "Wheeeeeee, I am free!!!!!" when I dropped it as I could not find it after that! Maybe tomorrow.

In an attempt to maybe get the passenger seat back in the car tonight, I went to my 95 SC seats, the driver side, which are in my carport. I wanted to take the motors out and put them in the passenger seat. Well, this proved to be and exercise in futility!! After all of the cleaning of the SC motors, I find that they are different, ever so slightly. It seems that the shaft is slightly larger on the 95 SC, or maybe in the 95's in general, for the rotors.

Anyway, after all of this, I am still stumped as to why these motors have issues. They are so basic, and I can assume that at some point, they worked ok. I did notice something that may cause the weakness in these motors...The brushes... I didn't get a pic, but noticed on my driver seat that the brushes were not contacting the commutator very well. I would say that only about 60 percent of the brush surface was actually making contact with the commutator. Could this be a part of the problem? If the brush is not making full contact, could it cause the loss of power and torque in the seats?

I may, in the coming weeks, actually take apart the gearbox assembly to see if there is a problem in there... If Ford used the same practices on the seat motors as they did in their power windows motors, plastic gears and such could be disintegrated in the gear box. I wouldn't put it past them...

Any thoughts, theories or other comments are welcome!

Thanks,
Phil
 

35th

Registered User
I have a 90 SC and a 97lx and both vehicles power seats suck incredibly slow lucky for me I'm the only one who drives the SC but my wife and I both drive the lx and it's like a month or so it seems to get the seat to move a year or so ago I found some same color lx seats as the current ones that where in great shape at a local salvage yard I bought them had the presence of mind to test out the power motor before I installed the seat and it didn't work so I took the whole thing apart but couldn't figure out how to remove the actual motor so I ended up just swapping the entire seat tracking which somehow made the seat motor slower... So to your point I assume is just a bad design which causes them to be extremely slow 30 some odd years later but if you come up with a reason/fix I'd like to know so I could fix mine I'm not that great at rebuilding electric motors so hopefully something else is our culprit
 

KMT

Registered User
Sorry if I missed it, have you cleaned and re-greased the tracks/sliders, confiming they offer as little resistance as practical?

Whenever I hear issues w/seat motors/movement, I think about all the past discussions that focused on gummed up tracks that needed more torque than they did when new w/fresh grease. As Chris notes, 30 years later isn't helping ;)

In addition, check for bent tracks, worn nylon runners etc. Anything that forces the motors to work harder can lead to fails that aren't the motor's outright fault, so...


About the commutator(s), a black surface is normal when the brushes are seated and helps operation. Polishing is fine, but if the brushes are new and properly run in, loss of torque can occur. I would have simply sprayed with electronic cleaner, wiped once, re-sprayed, confirmed healthy brushe (length and full matting surfaces), and called it good. If you're concered about proper contact, try to stretch the springs a tad, or pad the brush spring on one end.

Good luck.
 

KMT

Registered User
About the commutator(s)...

Sorry, should read:

About the commutator(s), a tarnished mating surface is normal when brushes are seated, and aids running operation. Gental polishing is fine, but if the brushes are new and not properly run in/seated, loss of torque can occur until a nice tarnish is re-established.
 

ricardoa1

Registered User
As Tim said manual tracks. I do miss the tilt feature in the seats, I need more recline on the lower seat so I don’t feel like I’m sliding off it. The replacement covers from SCP and eBay would take care of the non functional switches.
Tim have you thought about a way of propping the front part of the lower cushion. I used to have the electric ones fully up on the front and fully down on the rear.
 

Tim Groth

SCCoA Member
As Tim said manual tracks. I do miss the tilt feature in the seats, I need more recline on the lower seat so I don’t feel like I’m sliding off it. The replacement covers from SCP and eBay would take care of the non functional switches.
Tim have you thought about a way of propping the front part of the lower cushion. I used to have the electric ones fully up on the front and fully down on the rear.
I've not noticed the tilt honestly with the minimal amounts of seat time this car has over the last 7 years.

I've just enjoyed the fact that I am able to move the seat forwards and back without having to remove myself from the car to do so.

Also before doing the swap I researched rebuild kits. Appears they have rebuild options for fox/sn95 seats however the motors are nothing like the mn12 and the costs were stupid in comparison to a trip to pick-n-save.

-Tim
 
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