97 SHO with on going electrical issues

[benhamrick]

Electrical light started coming on intermitently and had the alternator replaced. Solved problem for about a week. Started again with power dropping. Replaced alternator again. Solved for two weeks with the return of the problem with more drastic power drop and a/c issues.

My mechanic seems to be stumped. Any thoughts?

[armonica]

Originally Posted by benhamrick

Electrical light started coming on intermitently and had the alternator replaced. Solved problem for about a week. Started again with power dropping. Replaced alternator again. Solved for two weeks with the return of the problem with more drastic power drop and a/c issues.

My mechanic seems to be stumped. Any thoughts?

Sure. The alternator itself doesn't have a whole lot that can go wrong with it. For Fords, they almost always have just the rotor and stator by itself. The thing that goes bad in those is the brush assembly. Depending on the model it has to be taken all apart to get to them or if you really know what you are doing you can do the external ones with the alternator still installed. If you have a new alternator, that part is not very likely to be bad. The other part to the alternator is the voltage regulator. This is the big differerence between an alternator and a generator of many years ago. The electronics are fairly simple. The lower the voltage, the more power the circuit sends to the rotor's coils. That in turn increases the magnetic field to the stator and makes more energy to recharge the battery. If the battery is charged then the rotor gets very little to no power.

So, did your mechanic change the voltage regulator? A lot of them don't. Some Fords also have an external set of diodes for changing the AC that the alternator produces into DC that the battery can store (and your car runs off of). They can go bad as well and in fact this is almost always the cause of a "bad alternator". Ask about that.

Finally I read this morning that a number of the Tarus's and sables have a wiring bundle that goes over the transmission and there is a sharp edge there. They found that over time this edge cuts through the casing of the bundle and then the wires inside. Sometimes they short, other times they get cut and make-and-break as you are driving. Eventually they will fail entirely. They recommended checking for this and repair as necessary. I'm working on a Sable right now and it isn't showing any wires yet but it is close. I''ll tape it off and put some sheet metal under it to protect it. That seems a lot easier than filing the edge down.

Armonica