Really old member needs help with comfort seats.

E28 technical advice asked and given! Troubleshooting, modifications and more.
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RetiredDoc
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Really old member needs help with comfort seats.

Post by RetiredDoc »

My one-owner (me) garage queen 1986 528e is driven most Sundays for about 20 miles each time. The rest of the time it shares a closed garage with my wife's car. Today I found that the power comfort seats do not adjust, neither the driver nor the passenger seats. I have no idea how long they haven't worked, since with the limited driving I never have had the need to adjust either of them. Here is what I have found, tried, and done so far.

1. Neither seat moves in any direction. However, when pushing each of the function buttons, I hear a faint click each time under the respective seat. The headrest buttons do work, and both headrests go up and down.

2. I tested and cleaned both seat switch controls. I actually have an extra one still in a box, brand new., and swapping among all three does nothing. All test the same with a multimeter.

3. Fuse #4 is good, and all the other things on that fuse circuit, like the cigarette lighter, are still working properly. There is battery voltage across the fuse 4 contacts. The battery tests good for resting voltage and starting voltage drop, and I removed it and also load tested it.

4. I cleaned and used Deoxit at the ground point near the battery, the ground point near the starter, and then I removed the driver's side knee panel, and did the same procedure with the grounding point located high above the brake pedal.

5. I cannot remove the seats to test motors since both seats are run back and cover the access to the 2 rear bolts. Being comfort seats, there is not a way to run them forward using a square bit and a drill like is possible with sport seats. I did tap everything I could reach under the seats with a hammer. Still no movements.

I find it beyond belief that all the seat motors would fail at the same time, so I am still looking for something shared between the 2 seats that might be causing a voltage drop to the motors. Any advice will be appreciated. Thanks.
kojo96
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Re: Really old member needs help with comfort seats.

Post by kojo96 »

Agree with you that all the motors going bad at the same time is very unlikely..

I had/have a similar issue on comfort seats in my car that isn't driven often, same clicking from under the seat. I found that if I tap the switch on and off repeatedly while in the seat and rock back and forth (depressing the forward switch button) it seems to free up the movement and the seat gets back to working correctly.

They seem to work correctly after this in all movements until the next time they quit. Probably time to pull them and re-grease everything.

Also, the seats can be unbolted as they are now but it is really a lot of effort to do so. You will have to destroy the bottom side plastic covers and work the 4 10mm bolts out that secure the seat to the seat frame. The outside is easier, the inside is very difficult as it requires you to contort in unhuman positions and turn those bolts a ¼ turn at a time. It is possible though, I’ve done it.

Try the tap,tap tap and rocking first and hopefully it gets them moving.
Blue Shadow
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Re: Really old member needs help with comfort seats.

Post by Blue Shadow »

Those 4-10mm bolts were the reason there is gear wrench. Can't be done in reasonable time without those wrenches.
garageboy
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Re: Really old member needs help with comfort seats.

Post by garageboy »

I'm looking at the ETM...

Humor me. It's a 25AMP circuit. Replace the fuse. Maybe it can carry enough current for the other items on the circuit, but is like an open circuit when you try a large-draw appliance (like a seat motor).

The ETM also says:
"If both power seats do not operate, check Fuse 4 and the power lead to the splice"

I do not understand what the "power lead to the splice" means, but I assume it means that since the power is spliced to the driver/passenger seat controllers, that is what it means. In the ETM that wire coming off Fuse 4 is 2.5 RD/YL. I suspect that is fine.

It also talks about checking G200, a ground above the brake pedal. Before replacing the 25A fuse, I'd check that.

The next thing I would do is, if the seat is high enough, try to disconnect the large electrical connector under each seat. Perhaps one of the controllers is bad in such a way to prevent any current being sucked into either seat's controller. Try one seat connector at a time, i.e. driver's connected and passenger disconnected; test driver's. Then swap; test passenger's. That would indicate a controller went bad and you can find them easily here or probably a junkyard.

And then, finally, the seat can be removed from the seat base. It's a total pain in the ass, but it is doable. I'd stock up on 1/4" ratchet parts and clever wrenches. In 10mm. That will allow more reasonable access to the assembly to determine if current is getting into the controller.

Hope this helps.
Galahad
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Re: Really old member needs help with comfort seats.

Post by Galahad »

Hearing the relays click and the headrests working indicates that it's getting power, just not enough. If I remember correctly the headrest motor is smaller than the others, and the other seat directions take a lot of current. I'd really clean the fuse 4 contacts, it sounds like it's high enough resistance to start messing with things.
garageboy
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Re: Really old member needs help with comfort seats.

Post by garageboy »

Galahad wrote: Jun 13, 2022 10:22 AM Hearing the relays click and the headrests working indicates that it's getting power, just not enough. If I remember correctly the headrest motor is smaller than the others, and the other seat directions take a lot of current. I'd really clean the fuse 4 contacts, it sounds like it's high enough resistance to start messing with things.
You better believe the other seat directions take a lot of current to life my fat ass up! LOL We are definitely in agreement on this one. :)
RetiredDoc
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Re: Really old member needs help with comfort seats.

Post by RetiredDoc »

OK, here is followup.

1. Replaced fuse #4, deoxit sprayed on fuse and fusebox contacts, plus a bit of work with 2000 grit sandpaper, and even tried removing the fuse and jumping the fusebox contacts with a substantial wire. Nothing, seats don't move, headrests still do. Still clicking from under seats when switches depressed.

2. Removed the G200 bolt for the second time, did my best to clean up everything for a better ground, and reinstalled and tightened the bolt. Not the easiest of jobs when I bought the car when I was in my 30's, but really difficult now in my 70's. Nothing.

3. Managed to insert probes into the red and brown large wires at the connector under the passenger seat, and applied power directly at that connector with a 12V battery I borrowed from my tractor. Nothing.

4. Vigorously rocked seats back and forth while sitting in them and repeatedly tapping forward switch down, then same with aft button. Nothing changed.

5. Tried the gearwrench advice on the accessible seat mounting bolts. The bolt heads are in a U-channel only slightly wider than the 17mm bolt heads and a gear wrench head will not fit. A socket will, however, and I removed the front pair of bolts to be able to lift the seat fronts maybe a half-inch for a little better access. There is absolutely no gearwrench access or socket access to the rear seat mounting bolts.

Any other advice? Thanks for the assistance so far.
garageboy
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Re: Really old member needs help with comfort seats.

Post by garageboy »

I'm not quite as old as you, and I'm definitely more challenged when working on my cars than 30 years ago... I empathize...

I think it is going to turn out to be one of the two seat controllers. That said, if you disconnect them both and only connect one seat at a time, I think you'll be able to isolate the bad controller (which is a plastic box near the motors in the base). I would disconnect the connector that attaches to the entire seat if you can reach it. It really requires two hands to hold each side of the connector, which is tough. Hope this helps!
Mike W.
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Re: Really old member needs help with comfort seats.

Post by Mike W. »

It does seem odd that both sides are a problem at the same time, but whatever.

Kojo was talking about removing the small 10MM head bolts that hold the seat to the base, not the base to the floor. They're still going to be a royal pain to get to though. They screw into the bottom of the seat which makes it even harder to see without an inspection mirror at the least, and as he said you might have to break the plastic trim to get to them.

I would first try to unplug and replug the connector that goes into the control box under the seat. Might be two each, I don't recall. See if a connection is loose or anything. I think it plugs in from the front, but it's been a few years since I've been under there. If that doesn't work, and it probably won't, I would try to manually power one of the motors. Yes I know it's tight down there, but you might be able to either disconnect the little plug going to a motor, or use wire taps and tap onto the wires with a lead out long enough to power up with a separate battery. Won't take a whole lot if you're not sitting in them, I've run seats in junkyards using a cordless drill battery. Make sure you're clear though because they can generate some torque. And of course if it tries to move in the wrong direction, just reverse polarity.

You might even consider jacking up the car from the side to get it a little higher and a better angle to work at. Jackstands of course, blah blah blah.

If you do manage to get them going manually, it can be possible to repair the relay boxes, I blew a trace on mine one time, somehow I got a wire crimped. Once I got it out, not easy, repairing the box itself was easy, I just opened it up and looked for the burnt spot.
RetiredDoc
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Re: Really old member needs help with comfort seats.

Post by RetiredDoc »

Success!

I used a whole $25 can of DeoxIT D100 and long tube and liberally sprayed every electrical connector I could see under both seats. I also sprayed all the female connectors to the seat switches. Both seats now are working. Now it’s time to unbolt the seats and get everything cleaned up and lubricated. And, since I’ve gone this far, maybe even re-upholster the seats if I can find a kit with Pacific Blue material for comfort seats.
Blue Shadow
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Re: Really old member needs help with comfort seats.

Post by Blue Shadow »

Kojo was talking about removing the small 10MM head bolts that hold the seat to the base,
Yes, that is the gear wrench use.

The wiring harness starts at the big C100 connector on the firewall under the dash. That plug might enjoy a bit of Deoxit, too. Glad the system is working again. D5 Deoxit would have been my choice as the carrier would have helped on the grease in areas. But your seats are working and you can move to the next steps.

I'm guessing you are going to pull the covers off the gear assemblies with the seats not moving or stressed to allow cleaning and regreasing.

It sure would be great if you could capture a few photos and details of issues and of course the results of the fresh lube.

In the vintage audio world. a few components used glugrease, a European specialty chemical that turns to glue after 25 years. Frequently used in automatic turntables to freeze the mechanism all these years later.

Good luck.
Panici
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Re: Really old member needs help with comfort seats.

Post by Panici »

RetiredDoc wrote: Jun 14, 2022 11:36 AM Success!

I used a whole $25 can of DeoxIT D100 and long tube and liberally sprayed every electrical connector I could see under both seats. I also sprayed all the female connectors to the seat switches. Both seats now are working. Now it’s time to unbolt the seats and get everything cleaned up and lubricated. And, since I’ve gone this far, maybe even re-upholster the seats if I can find a kit with Pacific Blue material for comfort seats.
Nice! Glad you stuck with it.
And props for wrenching on it even with the pains that come with age.
RetiredDoc
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Re: Really old member needs help with comfort seats.

Post by RetiredDoc »

After the seats were working and before I moved the e28 from my shop back into the garage, I thought I'd lubricate the driver's window channel, since the window had been sticking. A little silicone spray and done, right? Now 2 days of wrenching later, I have finally replaced the window motor and reinstalled the glass. Now I'm waiting on a replacement interior door handle to arrive since the original plastic handle fell apart in my hands. After much lubricant spray and disassembly I discovered the problem was the original motor. Luckily I had a motor left from over 20 years ago that I was able to use as a replacement.

I have to learn to say enough, but when I start wrenching on the e28 it's like being possessed by demons to just do one more job.
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