As a longtime electrical guy, I've always found that one of the best ways to start troubleshooting most electrical problems is with a schematic. A shop manual is a MUST for any DIY, --if just for the electrical schematics alone. For the price of an hour or two of labor, they're a real bargain. Chilton's, etc are okay, but the GM manual is really the best for most applications.
Okay, now that I'm off my soapbox, let's take a look at the problem. You've checked the (shared? --you're sure?!) fuse and it's good, so that leads me to believe it has to be common to one seat. Since the other seat works, you have something to compare it to. As Martha Stewart says, "It's a good thing."
Always start with the obvious. Get a flashlight and take a slow, methodical look under the seat, ensuring that there aren't any broken or chaffed wires, damaged or open (disconnected) connectors, that sort of thing. Follow the wiring harness as far as you can, from the seat switch, seat motor, to any controller, --as much as you can find without opening up the innards of the interior yet. Does everything look okay?
Bummer, I was hoping this would be easy. Let's move on. Again, using your trusty flashlight, unseat and inspect the connector faces, looking for corrosion or evidence of contamination (-remember that coke you spilled last summer when the cell phone rang while you were changing the radio station?) If all looks good, re-seat the connector(s) and try to operate the seat again. Still no good? Here's where it starts to get really fun.
If you're semi-proficient with a multimeter it's time to get into it. This problem is waiting, begging, teasing you to find it. If you're not handy, or intimidated by electrons find a new best friend to help you out, or get emotionally and financially psyched-up to meet your service department.
If you're still following this far, you're either holding a meter, chilling beer for your friend or throwing caution to the wind. I like that! Let's continue:
Using the good seat as a reference, draw a cartoon of the connector on the "good" seat controller switch first. With the connector disconnected from the switch, use an ohmmeter to "characterize" the switch in each of it's operating positions. Make a simple drawing showing each pin number (you can name them in any order as long as you do it the same for each switch.) On the "good" switch, measure across each pin until you see the different combinations of switch positions and "shorts" on the ohmmeter (0 ohms). Re-install the switch to it's connector and do the same thing on the other switch that controls the "bad" seat. If they don't match up, chances are you have a bad switch. That would be good. Otherwise, we'll have to dig a little deeper, (That could be bad, depending on your ability.) to ensure you're getting voltage to the switch.
Do the visual inspection and switch test, then report back what you've found and we'll take it from there.
PS: Tell me your experience level so I:
1) Don't talk down to you --my bad!
2) Lead you to a point where you're so stuck I have to get on a plane!!
Cheers!
CC
