Unplug the wire from the water temp sender. Start the truck & run it under load, same conditions that make the gauge peg. If the gauge pegs under those conditions with the sensor unplugged, you have a short to ground in the wire that runs from the sensor to the back of the cluster. Trace every inch of it, looking for worn insulation.

 

here is the connector I need

Here is the connector I need





Well, I found the problem, and it sure wasn't what I was hoping for.

I hopped in the truck, started her up, put it in drive, accelerated and BOOM! the temp gauge shot all the way up, and the oil pressure light came on. I stopped, and unplugged the temp sender wire. Tried again, and everything worked. So after taking a good look at the temp sender wire, the connector was coming detached from the wire, so I assumed it was grounding to the head. When I pulled the wire out to have more room to put an end on, I found the following mess (see pics). So it turns out that the temp sender, and oil sender wires were bare at where they entered the harness, and were rubbing bare wires together...GREAT! aaaaaaaaaand now most of my engine harness is trash (I was wondering where that burning smell came from....jk). Thankfully, most of it isn't even used anymore, so I can just cut out around ~80-85% of it, and fix the rest, although it still won't be an easy job. The temp, and oil pressure wires appear to be breaking apart where they go into the connector, that takes them inside the firewall. Does anyone know where I could source this connector?(see pics). If I can find a new one, I'll just tap into it's pigtail, and redo the entire wire for both of them. I also found the ground that goes from the block to the firewall, and cleaned it while I'm here. Now onto the fun part. Finding new wire that matches the old stuff, and replacing it correctly. Thanks everyone for helping me diagnose this disaster! Someday, this truck will get a full rewire (not by me, by a professional shop), but that day isn't today, or probably in the next 5 years either, but it's coming. Thanks again!

EDIT: I actually need the male side of this connector. I found the female side (SMP S698 on summit) but I can't find the male end. Any idea where?

 

The male side you will hack off an old DS II Box

Or just replace the connector with a 4 pin weather pack connector. ( the better option)

https://www.hipoparts.com/weather-pa...connector-kit/

 

I like the weather pack connector much better...i'll probably replace the other 3-pin connector while i'm at it. Thanks!

 

Ya they are the best option now, even if they are GM style connectors. For the 3 pin I would just use a 4 pin and omit the one pin. The flat connectors just look a little too GMish IMHO.

 

Eh, that's fine. The whole "GM parts on a Ford" doesn't bother me too much, especially if it's an upgrade... Hopefully these new connectors will be easier to unplug then the old Ford round ones... they're a pain!