Power seats only work with a door open. Cig lighter fuse blown. replace, now OK

wow, how insightful...

I am attempting to get an electrical schematic. Its quite odd that the fuse for the cig lighter blows, yet has nothing to do with the seats. I bought the car in Texas and drove it back to Michigan. In Texas, I noticed that the power seats would only work if either door was open. It doesn't matter which door is open. I checked fuses and found the cig lighter was blown. I replaced the fuse and the seats operate with the door closed. I plugged in my Phone/Nav system and drove 1200 miles. No problems. Once home, I had my wife do some seat adjustement reprograming which worked fine (Seat 1, 2 and 3 respectively). A couple of days later we went to take a drive and the seats would work until the door was opened. I checked the cig fuse, and it was blown. There is no heating element in the lighter.

IF replacing the fuse for the cigarette lighter makes the seats work , then they have a power source in common somewhere.Maybe the power outlet (lighter) is defective, if there is nothing in it , or if it blows the fuse when the adapter is used then it's possible the adapter is in someway incompatible with it. Maybe easiest to 'remove' it from the circuit (unplug) for a little while to eliminate it as a cause for the fuse blowing. You also stated that the seats worked at some point , with the doors closed. IF that remains the case , then at this point , that would rule out my theory of a broken wire in a door harness causing a short. Until you are able to get a schematic , stay aware of the conditions when the symptoms affect the seats (as you obviously have) and I'm sure that will help narrow the problem area down. Keep us posted I'm always curious as to the final outcomes of these things , but people rarely tell us because 'it's fixed now, why bother' , I guess. And I like to know if I'm actually any help.

What's odd is the lighter receptacal worked fine for 1200 miles with my Phone/GPS plugged into it. And I purposely did not put the heating element back in the ligter when I uplugged the phone. During the road trip, I probably opened and closed the doors a dozen times between fuel, rest and sleep stops. When I got home, I had my wife adjust the seat/mirrors to her liking and then programed button number one for her setting. I then set up my seat/mirror prefernces, and programmed number two. We drove around a little, then parked the car in the garage for a couple of days. When we went to drive it again, the seats would not work unless a door was open, and the cig. lighter fuse was blown. I definitely need a schematic.

I know this thread is 8 years old, but there was no followup on this cigar lighter fuse blowing issue. My 1995 SL500 just started doing the exact same thing as was going on with "MarksSL500". Internet searching shows this is a common problem . . . . but I have yet to find a solution. Someone has to have fixed this in the last 8 years. I know there is a short, but where? I'm thinking it is with the cigar lighter, which I use to power the satelite radio reciever. This worked for the 2 years I've owned the car, until this fuse blowing started and taking out the mirrors and seats also. There is only one fuse blowing. The drivers seat control module in the door was repaced as it was working, but very jerky and eratic. I didn't mind since the preset seat postion buttons worked the seat just fine. After repacing the defective seat module in the door the seat now works great, but still the cigar lighter fuse blows and with nothing in it, taking out the mirrors and both seats, unless the door is opened. Then they work fine, until you close the door. Scratching head . . . Any ideas would be appreciated! What is weird is the seats and mirror issue. With the cigar lighter fuse blown, they won't work . . . unless the door is open. This tells me there are 2 power sources for both the mirrors and seats and they switch over when the door is closed to a different power line ... which is connected to the cigar lighter circut. What do you think???