Problem with charging system?

Driving down the road I'll occasionally get three red lights on my dash lighting up (Brake, A/T and Battery), a soft glow to start with and then getting brighter. At the same time the voltmeter slides down from its normal 14 volts or so down to 12 or just under. If the headlights are on they dim a little, if the heater blower is on it slows a little, dash lights dim a little yet everything still works as it should. Anywhere from 30 seconds to 5 minutes later the three red lights go out and everything is back to normal.

The only other problem I've had (my guess is that its related) is a couple of times when I've unlocked the truck (with the key, as I don't use the remote) the alarm has gone off. Mind you, it wasn't set to begin with and almost never is. The remote would not stop it, nor would the silence button. Had to wait out the full alarm cycle. Both times I then got out, locked it with the remote, unlocked with the remote and all was good.

Ideas anyone?

Thanks,
Mark

Sounds like the symptoms I get for a charging system or battery problem. I'd check both to be sure. <img src="/forums/images/graemlins/kewl.gif" alt="" />

I have read that there is a diode that goes bad in the alternator that fixes these lights. I currently see the A/T, Brake, Battery, and Main't Req lights flicker on and off throughout the drive. They are also only lit about half as bright as the lights that are actually on.

For example, if they are on when I start up, the A/T light is brighter than the rest since it's actually on, then goes down to about 50% after a few seconds (when it should be off).

However, my voltage meter doesn't move, so they may not be the same issue. I'd start with your alternator though based on my readings. Someone with more experience may know more though.

Probably failing alternator - diode triplet likely cause, or internal voltage regulator. DO NOT buy a rebuilt from any chain parts house except perhaps NAPA - get yours rebuilt at a local shop or buy new.

There is a shop down in Kent that can rebuild it, the place looks like a single man operation. Took mine there and the guy was super knowledgeable and really nice.

The rebuild was over a year ago and have not had any problems with it. Don't remember how much they charged but want to say it was 50 or 60 bucks.

~ Jon

Electrical problems of this sort can originate from many different areas. The first question I always ask before diagnosing this type of problem is, ôHas anyone installed an aftermarket accessory?ö
If so, thatÆs were I head first. As an example, is that security system factory or aftermarket?
Test the alternator and battery as already suggested. A malfunctioning diode can create strange electrical problems. My guess is that you have a loose or corroded ground connection.
Look at a wiring schematic and check all grounds that affect the circuits involved. This includes direct connections and harness connectors.
Conner

Listen to conner....

I've had thast kind of alt light problem before. There's some kind of doohickey that only lights the alt light when the alternator is not putting out a charge which only lets the current to the light when a no charge state exists.

Ditto on the grounds. Clean the battery - post and clamp first...

When you have alternator problems those light will come on. Just put a volt meter on the battery while the truck is running, if it's not charging around 14 volts have it repaired. Make sure you don't have oil leaking on it as this will destroy in no time flat. I know, been there to many times.

You are talking about your 97 right?

This is the 97 (the 90 went to the great wrecking yard in the sky a few years ago) with the factory locking/alarm system.

Looks like I'll be spending some time with the multi-meter, wire brushes, emery cloth and slinging the wrenches a bit this weekend.

Thanks for all the help!

Mark

my bets on alternator failing.