Bad "voltage regulator" or alternator?

So, just as I was driving home this morning, my radio started to cut in and out, voltage spiked to 19v on the panel, and my "Check Gauges" light came on.

I assume that something went south or I have a loose connection somewhere.

Since the "voltage regulator" is in the PCM, and not in the alternator in my '99, I'm wondering if people have any thoughts on the best way to approach tracking down the problem? Obviously, my first thing is to clean and check all of the connections to see if it was just as simple as that. But, don't know the next steps -- could the alternator go bad and through out 19v without the regulator in the PCM going bad? I'd much rather replace an alternator than the PCM.

Thanks, help would be appreciated (and I thought my '99 was "new" at 68,000 miles -- guess I better get used to all the normal replacement/repair stuff that I haven't had to do to this point). -SNB

Some times when the alt dies it can take out the ECU.But that probably would stop everything.
Your on the right track,have the output checked on the alt checked befor throwing parts at it.
Wayne

Also remove and clean your battery terminals, and be really suspicious of a defective battery. The battery would normally not let the voltage rise above about 15-16 volts, but if it is bad, or connections are bad, it will not limit the voltage. Voltage spikes above about 18 volts are really hard on electronic components in your system.

Thanks for the replies so far. I definitely plan on cleaning up the battery terminals along with other electrical connections (alternatator, grounds, etc.). Luckily it started to flip out only a few minutes before I got home, so my hope is that no damage was done.

Thanks for the reminder to have the battery checked out -- even it is a nice gel-cell battery (Odessey), but I'd guess it rather be a bad battery compared with a bad alternator. Was looking at alternator prices last night and reman alternators for my '99 are list at $200-$300! If I do need to replace the alternator, may be time to check out some local yards to see if they can find one.

I'll let you know what I find out, luckily it will be a nice 60 degree day here, so a good day to spend on the Jeep. -SNB

Cool, after cleaning up all of the cable connections (alternator, PDC, PCM, battery, and ground) everything seems to be running fine and normal again. The alternator connection was really corroded so my bets are on that. Also I replaced the ground cable going from the negative post on the battery to the frame. I accidentally broke the connector to the frame when re-installing the battery on that cable (I didn't push it too hard when it broke, so it could have been already damaged).

So, don't exactly what the causes was, but I'm glad things are back up and running. Hope it stays that way. -SNB

What you experienced was a classic bad ground syndrome. If you have to, use your FSM to search out all the main grounds and make sure they are clean and tight. You might not be as lucky next time. Often times will pop expensive elec components.

Judd W. VA said:

What you experienced was a classic bad ground syndrome. If you have to, use your FSM to search out all the main grounds and make sure they are clean and tight. You might not be as lucky next time. Often times will pop expensive elec components.

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Yeah, unfortunately, I don't think there would have been a good way to have spotted the problem in the ground cable before it broke. It broke about 3/8" up into the heat-shrink wrap -- so there were no outward signs of wear on it -- until I took it off and re-attached it.

But you are right, definitely was lucky. And I did already today hunt down most of the major grounds and cleaned them in the engine bay. -SNB