we were driving on the highway and the head lights began to dim, the fan slowed and the battery gage would drop to about half. it seemed as if the alternator was kicking in and out because everytime the lights/fan would return to normal the battery gage would jump up to normal. eventualy the batery and brake dummy lights began to flash. as the drive was coming to and end, it seemed that the alternator had totaly failed with the batery and brake dummy lights staying on. so, we changed out the alternator and the belt(figuring that it was that or the voltage regulator), started her up and the brake and batery dummy lights are still coming on. we have 14volts off the batery and proper alternator belt tension. so now we don't know what else so do. it starts well and iddles well but we haven't taken it for a drive yet. any advise????

 

Man, I hate electrical problems.

Anyway, as with all electrical problems, the first thing to do is to check your grounds. Start with your battery ground wire, both at the battery and where it bolts to the chassis. If both connections look good, run a continuity check on the wire. Sometimes the insulation will look great but conceal a lot of busted wires. Then, if your alternator has a separate ground wire as opposed to being grounded through the bracket, check that out, too, connections and continuity.

You say you replaced the alternator. Do you still have the old one handy? If so, take it to a major auto parts chain store (Autozone, Pepboy, etc), most of them will test alternators for free.

It just doesn't sound like a regulator problem, because the function of a regulator is to keep the alternator from frying your battery, so its kind of a one way check valve to keep the alternator output below a specified level. But you never know, especially since you say the problems still occur with the new alternator.

 

Oops! Should've said "resistance" instead of "continuity." Many sorries.