sjgatley

My boy gave me a 93 taurus that had several problems. I have installed new cap rotor wires and plugs. Gap was at least twice what it should be they were so old(could not believe it ran). Repaired egr, new pcv, fuel regulator, replaced fan, new relay box. The problem is when Oreillys runs the "in car" battery and alternator test it says that alternator is charging and battery is excellent. My boy put both of these in new and his buddy had battery backwards at first. They had a big surprise. I have not found any shorted wires yet. The Oreilly's test shows bad diode and when I take the alternator out it shows good regulator, alternator and rectifier. The Oreilly's guy was surprised when he tested it because he checked it with the in car tester just a half hour before. Repeated the in store test three times and shows good. Went home put the alternator back in and put the new relay box that controls the fan back in and went back up and the Oreilly's in car test still shows bad diode. He says still shows excellent alternator and battery showed 98 % and in excellent working order. Engine now runs really well but I need to find this diode and fix. Any ideas of what it is referring to and what other things could cause this. How can I track down the problem and where should I look?

foggysail

Diodes and rectifiers are one and the same. REversing the battery connections to an alternator can damage the rectifers (diodes). Unless you're skilled, have access to replacement diodes (rectifiers), I suggest replacing the alternator.

But before you get carried away, does your battery charge??

sjgatley

oops sorry found and fixed. The alternator showed bad diode on Oreilly's in car test but showed good on in store test. Put used alternator in and it works. Thanks