Engine/Transmission (1994 - 1998) Fuel Pre-heater Wires.

[MHalloran]

Help! The two wires feeding the fuel pre-heater became disconnected. One wire is heavier (fatter) than the other. Does it matter which wire connects to which side? Thanks for the help!

 

[KWentling]

My service manual for my '98 only shows 2 wires, one in from the fuel heater relay and one out to ground. BUT, they are both 14 gage wires. The connector pin outs are cavity one "14 gage RD/BK fuel heater relay output" and cavity 2 "14 gage BK/TN ground" I doubt that polarity would matter on a heating element or the temperature sensor switch, but I would say the heavier wire would be from the relay and the lighter to ground. Where did the wires come apart? Maybe someone else can shed some light.

Kim

 

[MHalloran]

Kim... My truck's a 96. There's a connector in line (similar to the connection for the water-in-fuel sensor) but the connector is not the usual male/female type. It's like that but half the connector is not there. Let's start from the pre-heater and go backwards. I'm sure you're familiar with how it looks. Pre-heater has fuel temp sensor in upper half and heat element in lower half. Wired in series, these two wires (same size) come off the unit and each wire has a male end on it. Both these male wires are parallel encased in a plastic female housing. That's all fine and dandy. It's the two wires that are to feed this connector coming from the power source that I'm wondering about. Two feeds (supply & ground?) one maybe a 14 and the other a 16 each with a female end on each come out of a black plastic split loom wire protector and are supposed to connect to the males I mentioned above. Theres no "housing" around these two feed wires. Thought it was a strange set-up coming from the factory like this. This is where it became disconnected. Both females pulled off. My question is, does it matter which side I plug these two wires back in to make the "series" circuit? Being a 14 & a 16 concerned me. Don't wanna burn anything up.

 

[DPinkston]

I'm at work right now so I can't give any specific answer to your question, but if you haven't got a Haynes manual, my advice would be to get one. It has a pretty good schematic of the wiring and even though I'm no electrician I could figure out what goes where pretty well.

Danny

 

[KWentling]

I'm changing my oil filter later today so I'll take a look at mine and also in my '95 book and see what they have. Did you buy the truck new? I wonder if someone did a repair job on it maybe?

Kim

 

[JNailor]

When I fixed my burned connector some years ago, I remember that one wire had thicker insulation than the other on the truck side of the plug. Both were the same on the heater side.

I don't think it matters which way they go. I don't have my manual here with me now.

 

[KWentling]

I looked at mine when I did my service and there is definately factory connectors on it. I see in you're other thread someone may be helping you off the site. If you need I can trace the wire and see which goes where on the heater. I'll need to move my Prime-Loc out of the way but that is no biggie. Let me know. Truck is setting on jack stands in my shop because we are swapping tires around off of the truck we traded for the '04 CTD so the '98 will soon have nearly new BFGs.

Kim

 

[MHalloran]

Hey Kim-- Thanks for the input! Yes, I did buy the truck new. I was there when it rolled off the car carrier. So this wiring "configuration" came from the assembly point. Guess that's how they wire things in Mexico! (Yes, a lot of our trucks were made there. ) I shouldn't joke about this though, it's a 96 with 176,000 miles. Have had ZERO problems with it. A fellow TDR member Nick ventured out to his truck at 3AM in the dark to see how his was wired (that's TDR devotion for you!) Seems that it's in series: Heavier wire feed to lower heat element, then to upper fuel temp sensor, then out and back to other lighter wire. So I thank you but you can leave your Prime-Loc intact! Hey DKing, your 94 sounds like its wired like mine. Thanks also! Mike