Good morning guys. In the process of replacing my heater core and blower motor I have discovered a mess. I have wires melted together and some are completely severed. The more I dug into it the po has spliced and hacked into this all over the place. I want to replace the main harness and found one out of a 79 f150. It seems to be in good shape. I have found it online so I can't compare the two side by side. The fuse block is different but I don't know if that matters since it would replace the old one. My question is will it fit and plug into my 75 f250. Any help or advice would be appreciated. Thanks.

 

No, not very easily. This is an area that Ford liked to play around with and make changes every year.
Either stick with looking for the same year or go with something like a Painless wiring harness.
Also, if you decide to stick with the factory harness, be sure to get one that matches your dash. The cluster with gauges uses a different harness than the cluster with idiot lights.

 

And now comes the fun If you start tackling your whole wiring harness, you will be surprised at how all your truck projects go back to this point. Even angry if I may say so. If you are handy at wiring, I would suggest a 12 circuit fuse block to start, so you can do a circuit at a time. If you have the time, like TWO weekends (2nd weekend is to get the bugs out..... or why is the left blinker on when I signaled right??) you may wish to get the fuse block complete with harness.

Advantage to the first way is you can have a stopping point with each circuit. Second way is that the wires are usually marked.

Disadvantage to the first way is buying and marking the wires. I suggest a simple label maker and clear heat shrink. Second way, well once you are into it, you'll have to see it through, unless you want to bundle up your unfinished circuits.

One last thing: Your manual will be your best friend when tracing the lines to the rear or front and these pre-made harnesses usually do not include your Duraspark hookups

 

I have swapped cabs and front clips from different years, usually the plugs are different. If you swap make sure to get a repair manual that has wiring diagrams, If you splice the wires use heat shrink connectors, they are expensive but they are worth their weight in gold when it comes to future corrosion proofing and sealing.

 

Thank you guys. I guess I have some research to do. Easy heater job turns into rewire, bummer.

 

It helps to have the old wiring harness hooked up and document the colors and where they go under the hood and on the firewall plugs then hook in the new harness in and change accordingly at the firewall as some wires might stay the same

 

Search on here for wiring harnesses. There are some out there that are closer to original than paneless and have alot of the factory plugs.

 

I have been looking at centech. Has anybody dealt much with them?

 

I installed one not to long ago and was very pleased with it. Instructions were great, all wires labeled. Came with most of the switches needed. Call Centech and ask for Jim. They can tailor the harness for your needs.

 

I was thinking of calling them tomorrow. Makes it better to hear from real guys who have used them. This forum is great.