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Power Seat Wiring problems

16K views 9 replies 8 participants last post by  crdnblu 
#1 ·
I have picked up a nice set of leather seats for my 50 Mercury project that came from a 2005 Buick Century. I cannot get the power drivers seat to work. Under the seat is a MSC module (master seat control?) see attached picture. I have downloaded a simple wiring diagram from Mitchell but it does not show this module. I am not sure if the donor car had a multiple driver position memory system. I would really just like to get the basic seat functions to work. Can anyone tell me where I should be running power and grounds to get the basics to work. I have also attached a couple pictures of the seat harness connections. I know that the smaller one is for the side impact airbag which are being removed. Thanks for any help.
 

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#2 ·
I would "guess" the heavy gauge black and orange are ground and power for the motor(s), while the others will control the various functions. I'd hook those two up and use a jumper to toggle the other wires to each other, to power, and to ground and see what happens. Just a very momentary touch so as not to fry anything if the connection is grossly wrong...

Russ
 
#4 · (Edited)
late model wireing has whats called power grounds, its a backward type system LOL :D the switches don't supply the + power, the module and motor are hot and the switch grounds the seat to operate with the power ground! The big black wire looks like a ground- the big orange looks like power+ the small black and white stripe looks like a power ground The other small wires look like the seat wires for the different position controle buttons! Just a guess? you might be able to go to auto zone and get a schematic free ? But usually on the internet you have to pay for one! You can go to a public Library and check out a motors or Chilton electrical manual and get a schematic if the library doesn't have the manual ask them to get one for you to check out and they will get it from another library it only takes a couple of days! Or try a dealer and see if they will print you out one!

If your going to use a jumper wire to test put a Fuse inline so if you do screw up it will blow the fuse and not fry the system!

Jester
 
#5 ·
computer

The seats will have (3) motors. Each one of these motors will control one of the functions. Such as forward-back, tilt and high-low.
This is done by running the DC motors in forward or reverse rotation by reversing the polarity of supply power.
That's the basics of the power side but these seat motors have a position sensor that feeds data to the computer so that the seat can return to a preset position. Without the computer the memory function cannot be used.
Locate the motors and observe the wire gauge. There should be (2)large wires entering the motor and some other smaller wires.
The (2) larger wires will be the power wires the smaller wires will not be used.
Trace out those (2) larger wires to a connection point where you can test- power the motors with 12 vdc.
Power each motor but only for short period of time as the mechanism may be at the limit-of-travel. Then reverse the test wires and observe the rotation direction.
The attached schematic shows the fundamental arrangement to switch each motor.
I would recommend that you acquire a wiring schematic ALLDATAdiy.com Leading Source of Factory Automotive Repair Information for the donor car to know exactly how these seats are switched as relays are likely used and controlled by the computer. You may not be able to use these relays depending on the coil voltage.
If you decide to locate the switches in a center console then DPDT center-off switches can be used.

vicrod
 

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#6 ·
I had a similar delimma with Caddy Catera seats. My solution was to go to the dealer and look through their service manual. The solution was found in the "troubleshooting" section and involved a special wire that had to be grounded before the seat would work. This may not work for you, but it's worth a drive to the dealership if all else fails.
 
#8 ·
Thanks

Thank you for all the input. The wiring on these seats is much more complicated than any of the schematics that I have found or that you guys have been great to provide. It all has to do with the position memory functions and another module associated with it. Looks like I will have to strip out a lot of whats there and rewire the switches and controls.
 
#9 ·
The attachment schematic of an 05 Buick posted by Crownver is an excellent example of an 8 way power seat controlled by (8) SPDT switches with NO computer or relay module or memory module of any kind.

These switches are maintained in one position (all connected to the negative bus).
And momentary in the other position (as each switch is pressed it is connected to the positive bus.)

This setup becomes tricky if the switches are located in the door panels (to many wires across the door jam). If the switches can be located between the seats the wiring becomes more simple.

vicrod
 
#10 ·
Jumpers Worth a Try

Before stripping out the driver's seat wiring, I'd suggest that you consider the advice of Russ, & Jester. In my own experience with Cadillac Eldorado power seats, I found that by studying the passenger seat, I was able to ID the extra memory wiring in the driver's seat. Then, I found that only one permanent jumper was required to by-pass the memory module wiring, to make the driver's seat operate properly. It ended up being a pretty simple fix; worth a try, IMHO.
 
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