wiring a feul filter heater on a 1998 e300 td
 

hey, I bought a dc powered 100 watt fuel filter heater that I would like to install myself. From what I understand a typical way to do this is to connect the 12 gauge wire (+) to the battery and run it up to where I want it. My questions are these: what is the best route to take to get it to a place, maybe the middle console, to wire it to a switch, and from there how to get it into the engine area? Once I have the wire past the fire wall I can figure out the rest assuming I can run the negative wire from the heat pad to somewhere in the engine area.

Thanks in advance. Look forward to your responses

Is it a metal band that goes around the filter? If so, i'll tell you how I do it with my vegetable oil car. Basically, the heater is wired to a glow plug. When the glow plugs go out, the heater goes out. This way it never overheats and causes a fire. Glow plugs stay on for about 3 minutes i think. The idea is after 3 minutes the car and fuel are warm enough for fuel to flow through the filter. And it naturally gets warmer from there as fuel ciculates from engine back to tank.

Another way is to have a temp switch in a coolant line. The temp switch will open when the coolant gets hot. Your ground wire for your heater relay runs through this temp switch to ground. And when it opens, your relay gets no ground and your heater goes off.

A switch on the dash board is ok too as long as your heater isnt' dangerously hot.

I have temp switches if you need one for sale and can help you wire it up. But using coming off your glow plug relay is free and may be good enough. These Mb's get hot pretty quick.

Wiring it to the GP is a BAD idea. GP does not stay on for 3 min. It will go off after the engine starts or times out in ~45s if the purple line to the GP relay is disconnected. It will also cause un-balanced load on the GP relay, I am not sure what effect it may have.

The best bet is hook the heater thru a relay. You control it thru a 20A relay with a toggle switch since you do not have a thermostat to turn it off for you. If you use a toggle switch then there is no need to feed the relay with a switched 12V.