how much current can the cigarette lighter handle??
 

heres what i have done/trying to do. The car in question is a 83 300SD, i installed seats from a 86-91 W126, they bolted right in with the exception of the wiring which needed to be re-done. Now, for the drivers seat i have rigged up a momentary toggle switch that runs the headrest(power headrest), and that has been working fine for many months. Now, however, i want to rig that same setup up for the passenger side. The drivers side gets it's current from the cigarette lighter power wires, is it ok to tap the passenger's side one into that power source also? thaks in advance, i'm pretty sure it would be ok but i dont want to catch my car on fire!!! Thanks again,
Ryan

Fuse Block
 

Your best bet would be to locate an unused fuse under the hood (from some option that you don't have) and wire the electrical leads for the seats to it. That way you are not overloading an already heavily taxed circuit, and your new seats will be fuse protected.

Heres what i would do if i were you. Like kowached said, don't over load your already overloaded circuit. When dealing with anything electrical i always throw in a inline fuse. I've hooked up tons of extras in my Mercedes and My Jeep and there isn't any other way i would do it. This way, if something does get overloaded it just blows the fuse and not the entire electrical device. I learned this the hard way. I hooked up a set of fog lights to the same line as a winch and one day when i needed both of them at the same time. When i started the winch and it fried the entire line all the way to the battery. So be carefull and good luck...

-Biggs