The mystery of the electric seats

[imautoparts]

My 1999 C280 (usa spec, no seat memory or seat heat options) has intermittent power seats.

I went to the dealership and bought the comfort and convenience relay. Came home, read a bunch of posts about it - and went looking in the trunk.

Trunk completely apart - no relay.

Went back to the dealership, and watched with amusement while the service manager, parts manager and a technician spent almost an hour looking in every nook and cranny under seats, under hood and of course in the trunk.

Their final answer: Your car doesn't seem to be equipped with that relay.

I'm not completely doomed; the seats work fine if I slllllooooowwwwwllllyyyy turn the key to "on", but will usually stop working again after driving a mile or two. If I turn the key rapidly they won't work 99% of the time.

If I don't have the key in the car and open the door they don't usually work either.

It is a mystery. Any suggestions?

[W202FTW]

My 1999 C280 (usa spec, no seat memory or seat heat options) has intermittent power seats.

I went to the dealership and bought the comfort and convenience relay. Came home, read a bunch of posts about it - and went looking in the trunk.

Trunk completely apart - no relay.

Went back to the dealership, and watched with amusement while the service manager, parts manager and a technician spent almost an hour looking in every nook and cranny under seats, under hood and of course in the trunk.

Their final answer: Your car doesn't seem to be equipped with that relay.

I'm not completely doomed; the seats work fine if I slllllooooowwwwwllllyyyy turn the key to "on", but will usually stop working again after driving a mile or two. If I turn the key rapidly they won't work 99% of the time.

If I don't have the key in the car and open the door they don't usually work either.

It is a mystery. Any suggestions?

Yay electrical gremlins!

Start with pulling the seat out and checking the the harness connections and pray that it's nothing else.

[Sulaco]

Seat relay is in trunk underneath big plastic panel. Remove carpet panel. See big 3 plastic screws holding the plastic panel down. Remove.

Underneath is a solid black relay. If you're standing at back of car looking in trunk, it's the upper level above the spare tire well. NOT the convenience relay that is located by battery. NOT the green relay beside battery and fuse box (that is fuel pump relay).

This is a common problem on 10+ 202's. Relay wears out. Some people pop the cover off and clean the contacts or resolder the joints. It's a cheap relay. Like $15.

[imautoparts]

Nope - no relay of that type in the trunk of this car at all. The plastic cover/3 screws were the first thing I removed looking for the relay.

[mbsickness]

Isn't the comfort and convience relay behind the door card on the update cars?

[imautoparts]

Please explain - are you saying in the driver's door I should be able to locate the relay? Also, define "update cars".

[mbsickness]

I seem to recall that there was a module behind the door card that controlled some electric items such as the window. This was from a DIY on adding puddle lights to each door which of course I can't seem to find. Update cars refers to 1998-2000 model years.

[Sulaco]

That's interesting. I've had 3 w202's: a 94 and a 95 C280 and a 99 C43, and the relay is the same on all 3. I have no explanation!

[mbsickness]

Sulaco, since you have a 99 I must defer to your experience. I have to tear into a door the next time I find a 98 or 99 202 at a pick n pull. BTW how is your car coming along?