Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Wiring harness chewed through

Some little critter chewed threw my sister-in-law’s wiring harness on top of the engine on her ford focus. A total of 7 wires have been severed. I attempted to solder them back together, but I ran into a few problems. I hope you guys can give me some ideas.

First of all, there are no big spark plug wires like I am used to. There are just little low voltage wires that go to little black cans on top of the spark plugs. What is going on here?

Second, some of the wires are chewed right down to the connector and there is barely anything to solder to.

Third, there are two green wires with yellow tracers. I don’t know how they match up. What are the consequences of screwing it up?

Fourth, there are two green wires with red tracers (going to the black can thing). I don’t know how they match up. What are the consequences of screwing it up.

Can you replace the parts with those from a salvage yard? That would be my suggestion.

The ‘black can thing’ is the coils-over-plugs (COPs). Instead of a single coil firing a spark for all the cylinders, sent to each cylinder through a distributor, cars have either coil packs or individual coils with spark plug wires or COPs.

Because of the high dependence of electronics in today’s cars, I’d go with Waterboy’s suggestion of getting a replacement harness from a salvage yard. If you hook the wrong wire together, you could do very expensive damage. Also, if the solder joint has a slightly higher order of impedance than the original circuit, it will cause all kinds of havoc. Some of these circuits work on voltages of less than a volt and have a very low tolerance for iffy circuits. Since some of the connectors are not to be saved, replacing the entire harness fixes that problem.

You should be able to ascertain where these wires came from and where they are going…Im not sure how you are getting confused…and that confusion is very important…NONE of these wires are interchangeable. All must be repaired and put back together properly…there are no alternatives… YOu can go to and auto parts store and get the manual for the car…it will have a breakdown of all the wires and their colors…again Im not sure how you are getting confused…as you didnt add or subtract anything here…youre just putting them back in order.

If you found the car in the yard you MIGHT be able to take the engine harness off the other car…but they must be the same car, same year same everything…sometimes hard to do. But if yo found it then its plug and play…A LOT of work to go thru just for 7 damaged wires…NO?

TRY VERY HARD to figure out whats up with your wires…fixing 7 wires is by far the easiest way out of this…and DONT F it up…it will lead to other unpleasant things happening. Hope this helps… Let us know if you have more questions and we will try to assist.

Hayne’s or Chilton’s manuals don’t have detailed wire diagrams anymore. Today’s car wiring is too complicated. The last Factory shop manual I purchased for my 2000 had a separate volume for the wiring diagram.

Well, the two G/R wires go to one of those black cans. I’ll have to check on the G/Y’s. So if that’s just a coil, and the two wires are the same color, I’m thinking they probably are interchangeable. Probably the impedence problem isn’t much of an issue if it is just going to a coil either. Can’t mess anything up too badly. I’m tempted to give it a try.

You can go to and get online access to the full factory wiring diagrams for the car. It’s $11 for three days or $20 for one month. Either way, it is much less expensive than damage to just one coil or the PCM.

Well, after talking to the guy at the Ford dealer parts desk, I decided to try soldering it. The new harness would have cost $700.

I obtained a wiring diagram from for $11 and I was able to figure out where everything went using an ohmeter. The connector going to a COP was chewed too close to solder, but fortunately the dealer sold a repair kit for that connector for 30 bucks, so I got that and soldered it in. The other connector had one wire that was not solderable, but I just cut off the other side and spliced in a piece of wire to bypass the connector altogether. I wrapped it up with some shrinky tube and stuff.

So far it looks like a 100% successful repair.

Nice work…crack a beer. Incidentally…if you look into this I believe that there is an Aerosol spray that you can use on your engine compartment that is a deterrant to rodents and the like. Not sure what its called but you can find it…May be a good idea to spray it around your engine.

I recall that many Datacenters used to have old Bus and Tag cables running under the floor for their Mainframe days. WHen they were pulling those cables out I remember asking someone “What the Hell is that smell” It smelled like Formaldehyde…(I believe it actually was Formaldehyde) he said that they use that in the Cable housing to deter rodents and it worked…Maybe that spray has the same crap in it…Hope not…it STUNK…I imagine they use something else now. Look into it.