just finshed a rebuilt on my motor and the shop putting it together notice the engine wiring is burnt n crispy n melted together from the heat. So WHAT SHOULD DO get another 5 speed FD engine harness or repair the wires?

 

That is a common wear item on FD. The wiring harness should be replaced if the wires are crispy and breaking and melting.

You can buy it new from Ray Crowe at Malloy Mazda. His number is in the 3rd gen FAQ thread stickied in this and the 3rd gen forum. Its about $850 or so.

If you want to try finding a used one, post a WTB ad in the Classifieds or use the Search feature to search for one.

 

IMHO, yes start with a new factory harness. This will cost about $850 from Ray. (You can call your local dealer too for a price but I'm warning you don't **** your pants when they tell you). If you attempt to reinstall it and there is a short or open, you will have a problem that can appear at any time and possibly create major engine damage.

There are two major problems with the factory wiring: 1) they wrap with common electrical tape and vinyl sleeves and 2) the heat under the hood. Oil leaks certainly don't help if there are any.

For item 1, I recommend buying self-fusing silicone electrical tape (A few rolls of 1" wide tape is plenty and having leftovers is always good). Cut off the vinyl sleeves and rewrap with silicone. I then replace or wrap over the electrical tape. Focus on the hardened areas of the old harness.

The issue of heat can be improved by standard FD cooling mods, particularly the downpipe, larger radiator, lower thermoswitch, and a vented hood. (Vented hoods aren't for everyone but they work).