Where exactly is the fuel oil heater

[needbigtruck]

Since my truck died in the cold a few weeks back (see "the cold killed my truck") I can't stop thinking that there must be something else wrong. Is that little wire that connects to the top of the filter the wire for the heater? If so how does it work? Is it on all the time? Where is the fuse ? The truck has been through 3 winters and every one has had it

[madmatt]

As the fuel enters the filter, the fuel passes through the fuel heater. The heater contains a thermostatic switch that opens or closes to turn the heater OFF or ON, depending on the temperature of the fuel.The fuel heater is operated by a built-in thermostatic switch. The thermostatic switch completes the circuit for the fuel heater element when the thermostatic switch senses a temperature below 59.8

[Jim Brzozowski]

Why would it need to come on at such a warm temperature?

[needbigtruck]

Well if it's only turned on by the temperature of the fuel, how do you test it to ensure it's working? If it's heating the fuel as it comes into the filter then I shouldn't have had a problem 5 miles down the road, the fuel should have been heated above the waxing point, unless it waxed up somewhere else, may be the little return heat exchanger mounted by the tank?

[madmatt]

I don't know why picked that temp. As for Diag, there is a 15a fuel ht fuse under your hood that should be hot in start or run position from there the circuit goes to your fuel heater. it is a red wire that goes into your heater. this should be hot the same as your fuse. the other wire is the black ground wire from your heater. To test I would hook the ground of a 12v test light to the ground circuit of the fuel heater plug then probe the hot side. it should light up. if not I would then see if it was a power or ground issue. Also FYI the wires coming into the plug for your fuel heater are different color then the heater wires themselve. Pink is hot and the black w/ yellow tracer is the ground.

[needbigtruck]

Thanks madmatt. I finally got a chance to do some diagnostics. I found the fuse and checked the voltage. Everything was fine. I also checked the current draw. I got about 4.5 amps steady state with about 7-8 amps when first starting the engine. I was hoping someone would have the specs for this. Thanks

[madmatt]

can't find any amperage specs.

[royalglen]

Madmatt is correct-There is no specs. re current draw. In my 03 service manual it walks you through checking for faults but only with test light. It is page6-2829 to page6-2831 in the 03 manual if you can find one!! Hope this helps you.