THE FICKLE SEAT OF POWER (Car repair)

© 10/20/06, 8/26/08 Soowee.
All rights reserved.

There is a certain lack of information regarding the rebuilding of power seats, including the electrical switches and seat actuators, and this becomes a problem with restoration of older cars, where such hardware is no longer available from the factory, and used stuff may also be just as unreliable as what one already has.

This happened to me during the “rejuvenation” of my six-way electric seat in my ’64 Oldsmobile 98 convertible. Starting about four years ago, I took the seat out and disassembled the solenoid transmission under the seat [Figs. 1 & 2], which was gummed up with what looked like old, hardened lithium grease. After 40+ years, it was no wonder! I took everything apart, cleaned it up and re-lubed the guts and put it all back, but the control switch on the armrest had a dead spot in it and would not move the seat back. So, I used a jumper wire to put the tracks in the correct position, then I unplugged the wire to the motor and solenoid transmission so no one else could run it up (I am really big). I later installed another switch bought from a parts supplier, and it is now working fine.

Now, I will attempt to address here in two parts both the electrical issues and the mechanical issues inherent in fixing electric seats. It may well apply to brands other than GM, but that is what I am working on, so I cannot vouch its application to, say, Ford. It may also have some relevance to working on other devices, but the reader is on his or her own.

NOTE: the terminology used herein is my own since I do not have access to a GM parts list.


PART ONE—ELECTRICAL ISSUES:

The first order of business is to determine complete current flow of a full 12 volts to all of the components in the circuit. [Fig. 3] One may rehab the mechanical parts of the seat first, as I did, but it won’t work until the electrical circuits are functional, and if it takes the average reader as long as it took me to get “a round Tuit” (around to it—four years), then the mechanical stuff may well gum up again for lack of use! After fixing the electrical stuff and still suffering balky solenoids, I had to disassemble the seat AGAIN and fix those problems—AGAIN!

Any factory manual is worth having to follow the proper procedures, but it helps to have some knowledge of electrical circuit testing. The drawings and diagrams in the Olds factory manual were invaluable, but the switch disassembly was all my own doing. Note that the Olds factory manual for 1964 addresses the six-way seat operation both in the "Electrical/Accessory" section (12) and also peculiarly in the "Body" section (16), the latter actually having more information and diagrams.

Power comes from the ignition-switched 25-amp fuse in the upper right corner of the fuse panel [Fig. 4] that also serves the power windows, the power antenna and the cruise control. Beware operating all of those devices at once, for it may blow the fuse, especially if any of them are balky and sucking a lot of amps. These devices are on the “Accessory” circuit so they will operate with the key in either the “Acc” or “Run” position.

Before checking the circuit, it is necessary to be sure the ignition switch is off, then remove the ignition key, then remove the seat switch. One should also first disconnect the negative battery cable for extra assurance. In my car the seat switch is in the armrest panel with the window switches. In some cars it is located in the left side of the seat itself, and those switches are wired differently, so the factory manual should be checked. I had one screw to remove from the front of the armrest, and another back under the inside door handle to loosen. [Fig. 5] I then raised the armrest panel top about 4 inches and popped the plastic wiring harness connector off the bottom of the switch held in place by two spring-steel clips on the underside of the switch. [Fig. 6] I then removed the switch itself by removing two short screws holding it snugly in place, and I pulled the wiring harness out clear for circuit checking. One can remove the entire assembly from the armrest panel first, then disassemble the switch assembly.

The switch itself has 6 pins on the underside [Fig. 7] that conduct current to and from the switch assembly through 6 sockets in the plastic harness connector. [Fig. 8] Those respectively are 12-volt hot (battery), (motor) field-forward & up, field-back & down, horizontal actuation, front-tilt actuation and rear-tilt actuation. One of the two directional motor-field connectors must be energized by the switch while simultaneously actuating one of three solenoids next to the motor under the seat. Each electro-magnetic solenoid, in turn, drives a pair of cables to the respective left and right actuators (pair), three on each seat track. [Fig. 9] The front actuators tilt (raise or lower) the front of the seat, the rear actuators do the same for the rear of the seat, and the center actuators move the seat forward or back on the tracks. When one seeks to raise or lower the seat level, it energizes both front and rear actuators simultaneously. The electric seat motor reverses direction to accommodate these parameters via the field windings in the motor.

I first sought to clean the switch harness connector in the door (as distinguished from the motor/transmission harness connectors under the seat) by tightly rolling a small tube of fine-grit sandpaper so that it was no more than a couple of millimeters across. I used a piece of sandpaper that was about two inches long by no more than 1/3-inch wide, and rolled it the long way (rough side out). I took this small roll and repeatedly twisted it into each of the 6 tiny sockets on the switch harness connector [See Fig. 8] to clean the inevitable corrosion off the contacts as best as possible. I used a can of compressed air to blow them out, frequently changing the grit surface on the sandpaper.

Now, the only operational difference is determined by the location of the switch, which has reversed parameters for either the armrest or the seat-side locations. As noted above, the seat mechanism moves horizontally front to rear, tilts the front and tilts the rear. The switch has six metal contacts inside which trigger the motion functions.

Disassembly of the switch is tricky. Do NOT try to pry up the four flat lugs holding the switch assembly to the underside of the switch housing. [Fig. 10] They are part of the spring-steel clips and could suddenly snap off and hit you in the eye! You will then have a big hospital bill, be blind in at least one eye, and you will STILL not have fixed the switch! You may also break the flimsy pot-metal switch housing. There are four spring-steel clips holding the internal switch parts inside the pot-metal housing. The two spring-steel clips on the sides are the longer ones that also hold the plastic harness connector fast to the switch assembly. Remove these first by GENTLY rocking a thin screwdriver blade next to each larger side clip inbetween the housing side and the switch assembly plate to provide just a bit of static tension on the clip itself. Then one should use the tip of a punch to GENTLY push the small retaining spur or snell on each clip past the little hole near the edge of each of the four sides of the pot-metal housing so that the clips may be CAREFULLY withdrawn. Do this successively with each of the four clips, and GENTLY withdraw the switch assembly therefrom. Be careful not to drop one of the tiny end clips where it gets lost (like I did while disassembling the device again to take the pictures for this article!)

There should be a small piece of sheet plastic covering the copper switch contacts (sandwiched between those contacts and the button assembly) to inhibit moisture on the contacts. [Fig. 11] My plastic sheet was slightly perforated from years of use, so I put some plastic electrical tape on the underside to block the perforations before I reinstalled it over the later-cleaned contacts, some of which were badly corroded initially. The plastic should protect the copper contacts from spills, rain, etc. on the armrest. Clean the contacts with the same fine-grit sandpaper, being sure to clean each facing pair of contacts underneath each overlay copper strip, then blow the resultant dust off with the compressed air. I also used the sandpaper to remove some of the surface corrosion off the pot-metal switch housing and removed the button assembly [Fig.12] and cleaned it as well. The three buttons rock or pivot over top of the various paired contacts closing and opening them alternatively. The circuits thus energized reverse the two field windings for the motor to reverse direction, energize the forward or rear actuators to tilt or the horizontal actuators to move forward or back.

After cleaning the switch assembly and its harness connector, I first checked continuity through the switch assembly with the ohm settings on my multimeter by activating the various buttons and making sure that completed, low-resistance contact was made at all the pins in the proper order. NOTE: DO NOT USE THE OHMMETER SETTING ON A “HOT” WIRE! All current must be completely disconnected from the circuits, or you will burn your multimeter up!

The No. 1 pin is the “HOT” feed when energized, so I checked for possible resistance from that pin through the rest of the circuits. One must check that the circuit resistance throughout the switch is not excessive, less than 0.5 ohms. After reconnecting the battery cable(s), the key should be turned to the “Acc” position to energize the circuit, making sure the under-seat connectors to the motor and to the solenoid transmission assembly are all disconnected. Using the multimeter as a voltmeter, with the black lead on a good ground, one checks for 12 volts at the following places in the following order, being sure to not perforate the wiring insulation or break the connectors:

1—Fuse panel;
2—No. 1 socket on switch harness connector—should be “HOT”;
3—Reassemble the cleaned switch assembly and rejoin the cleaned switch harness connector to it; check the under-seat motor and solenoid transmission harness connectors (switch buttons must be activated) for proper voltage. [Fig. 13]

If at least 12 volts are found successively at these locations, then the electrical circuit is functioning properly. If less than 11 volts is found anywhere, there is a current-robbing voltage drop (“V-drop”) somewhere between the place checked and whichever prior one which was OK, and it MUST be fixed. There really should be no more than ½ volt dropped between the fuse panel and the motor and solenoids; any resistance between (such as loose connections or corrosion) can cause a “drop” and starve the motor of much-needed voltage. That will cause the motor to instead pull excessive amperage (current) and may heat things up and/or burn some wiring somewhere or even burn the motor up.

For the unfamiliar, voltage drop is checked (like all voltage) in parallel with the circuit or loads. [See Fig. 3] One meter lead or probe is put at the fuse panel, for example, and the other lead or probe is inserted into the back of the harness connectors (“back-probe”) [See Fig. 13] to the seat motor and solenoids, for example. With the key on “Acc” and the switch buttons successively pushed to activate the seat circuits, if any reading during an activation shows a “drop” of more than 0.500 volt, then that specific circuit must be fixed. Starting at the fuse panel, the remote probe should be moved further and further away from the probe at the fuse panel, checking the voltage at each point in the circuit, until possible offending component(s) is/are identified. Then the probe at the fuse panel can be moved toward it until the offending link is narrowly identified and then repaired. Be sure to back-probe connectors in place as the circuits must be complete and working to measure voltage drop. One should also check the V-drop from the fuse panel to the back of the “Hot” wire connector to be sure there is no significant drop in that feed. Then the circuits may be checked from the back of the “Hot” connector to the back of each of the other connectors as the switch is operated, then from the respective switch connectors to the remote connector(s) on the motor and solenoids. NOTE: the motor and solenoids will eat up whatever voltage is left over, so if the circuit is checked to the seat frame (though which the motor and solenoids are grounded) then a full 12 volts drop will likely show on the meter. The idea is to check what actually GETS to the motor and solenoids (ideally a full 12 volts), not what is used up by them.

It is now time to address the rehab of the mechanical components.


PART TWO—MECHANICAL ISSUES:
First disconnect the negative battery cable to keep any current from flowing through any circuits. Disconnect all under-seat wiring harnesses from the motor and the solenoid transmission under the seat and (optional) remove the seat cushion(s). There are usually four flanged ½-inch bolts that hold down the seat frame assembly to the floor pan, and they should be removed. One may need a U-joint on a socket extension to get to the “rear” bolts on each side of the seat tracks. NOTE BIG TIME: there is also a ground wire from the seat frame to the car floor [Fig. 14], also held in place under the driver’s seat by a fifth flanged ½-inch bolt. That must be completely removed and disconnected from the floor to get the seat out.

If all the wiring is disconnected, the seat frame assembly should come out of the car easily and may be turned upside down on a protected surface on a table [See Fig. 1], thus exposing the motor and solenoid transmission assembly for removal. Disconnect all drive cables from all six actuators on both seat tracks [See Fig. 9] and remove the solenoid transmission. Check the motor for proper lubrication and leave in place unless it needs rebuilding—probably not. There is a little “driveshaft” from the motor to the solenoid transmission that should be set aside in a safe place.

Remove the solenoid transmission by first removing the two bolts [Fig. 15] holding it to the seat frame. There is an aluminum “keeper” strap across each side of the solenoid transmission where the cables attach to the transmission. [Fig. 16] It is necessary to unscrew those “keeper” straps to remove the 6 cables from the transmission. There are two screws on each strap, and they have really weird socket holes in the tops that defy ordinary screwdriver fittings, so I used the short end of an Allen wrench to loosen them (a Torx bit might work also). Then disassemble the transmission by separating the case at the mid-seam held by a Phillips screw on each side. There are three solenoids inside which attach to the exterior cables on each side.

There are a pair each of blue, yellow and black cables, the short ones going to the left (driver’s) side and the longer ones going to the right (passenger) side. [See Fig. 1] On my Olds the yellow cables drive the front actuators, the blue cables drive the rear actuators, and the black cables drive the center actuators. They are made like speedometer cables. Be sure that none is kinked from trying to drive that gummy old lubricant inside the solenoids or actuators. Replacements are sometimes available from “USA Parts Supply” in Kearneysville, WV.

Open up the transmission case and clean the old lubricant thoroughly off each component therein and re-lube with nonhardening material, like white lithium grease or anti-seize compound, then reassemble the solenoid transmission. Energize with a 12-volt source to be sure the solenoids are easily engaging. I keep a charged spare 12-volt car battery on my workbench for such purposes.

The next step is very time-consuming and rigorous: remove and disassemble each of the six actuators and clean them thoroughly also, ONE AT A TIME. I started with the rear actuators [Figs. 17 & 18] and cleaned all the gummed-up white grease out of each of them [Fig. 19], using the point of a screwdriver in the grooves of the gears. It was hardened in the teeth of the gears, so it took a long time. It was substantially impervious to an electric wire wheel!! But for the rear actuators, it may be necessary to actually move the seat tracks fore and aft to get to the mounting bolts for the actuators, so I used a cut-nail in an electric drill and stuck that into the center actuator to move those tracks. Don’t let it jam hard against the track stops as it will jam the nail in the drive hole.

The front and rear actuators work as follows:
Torque force is applied to the input worm gear by the cable. [See Fig. 19] The worm gear engages a drum-like spiral gear inside the housing (that is where the old grease is built up). As the worm gear spins the spiral drum, a threaded rod or “piston” of sorts rides up and down inside the drum on internal threads, moving the seat corner up or down. The far end of the piston engages a slot on the underside of the seat to keep it in place, held in place by a 19 mm. nut that also holds in place a spring-steel clip about 2 inches long on the far (upper) side of the seat-track scissor. [Fig. 20]

Disassembly is fairly straightforward for the front and rear actuators. The track will pivot up toward the front of the seat when disconnected from the rear actuator. [See Fig. 17] But, I could not figure out a way to disassemble the center actuators that move the seat fore and aft, so I removed them from the tracks (BEWARE the tension spring, see below) and just sprayed them thoroughly inside with brake cleaner and let that drain out, hoping I was getting them cleaned up. I then sprayed the insides with white lithium grease and am hoping for the best. When removing or reinstalling the center actuators, there is a small coil spring sitting inside the scissor track assembly on a vertical post aft of the center actuator (don’t pinch your fingers working on this system). [Figs. 21 & 22] That spring provides tension against the body of the center actuator to keep the actuator pinion gear engaged in the teeth on the seat track. That spring must be relocated in place when reinstalling the cleaned center actuator on each side. Note its assembly before removal of the center actuator. When reinstalling the center actuators, while tightening the two flanged bolts that hold each center actuator to the track (the front and rear actuators do not use flanged bolts), you may want to push the drive pinion off the track rack just a “hair” (against the spring tension with your thumb) to keep the pinion from binding. After I cleaned and reinstalled the center actuators and the springs, I re-lubed the pinion and teeth on the seat tracks with white lithium grease.

Before reinstalling the front and rear actuators, check the track scissor lift actuation. Each side should move easily without binding. When reinstalling all of these actuators, it is necessary to check the piston depth on the bottom of each drum gear inside the front and rear actuators for even depth, especially left and right. [See Fig. 18] It is also necessary to be sure that the seat tracks are in the same fore-aft location respecting the center-actuator pinons. The left and right seat sides must move in tandem with each other in all modes.

After the actuators have been cleaned and reinstalled, reconnect all cables and energize the system with a 12-volt source to check ease of operation. Be sure and operate a pair of actuators together, preferably with the control switch in the car. One may even check voltage drop to the motor and transmission again to be sure. Reinstall the seat, making sure to connect the ground cable under the driver’s seat. Tighten the track bolts snugly and rock the seat to be sure there is no play in the bolts. Connect the under-seat harness at both the motor and the solenoids and work the operation with the switch again to be sure it is fully functional.


FIGURES REFERENCED:

Electrical work:

1—Under-seat view
2—Solenoid transmission, cables
3—Seat elec. circuit diagram (modified)
4—Fuse panel diagram
5—Door handle, plate removed
6—Switch assembly
7—Switch pins
8—Connector sockets
9—Track, right
10—Switch clips, lugs
11—Switch contacts, moisture sheet
12—Switch buttons
13—Motor, solenoid connector


Mechanical Work:

14—Ground wire
15—Solenoid transmission bolts
16—Aluminum cable “keeper”
17—Actuator, right rear, assembled
18—Track, right--up position
19—Actuator, right front, disassembled
20—Actuator, right front, 19mm. nut anchor
21—Spring, right track, w/center actuator
22—Spring, left track, w/center actuator


All photographs (Figs. 1, 2 and 5-22) © 8/26/08 by Soowee. All rights reserved.
Figures 3 & 4 taken from the 1964 Oldsmobile Service Manual, © Oct., 1963, Oldsmobile Division, General Motors Corporation.