Help With Intermittent Charging
 

On a recent 1400 mile run to Salt Lake City from Seattle and back my trucks charging system began acting up. I think it must've began sometime on the way down I noticed the voltmeter on the batter showing low voltage readings and dim headlights. When I noticed this I would quickly kill the heater and radio. After awhile the voltmeter would bounce back up to 16 volts or so and sometimes stay there for a few hours and sometimes only a few minutes. On the way home about 20 miles outside of Boise at about 11pm my alternator decided to crap out completely - speedo went dead, engine lights came on (although very dim) and the head/taillights were just barely illuminated. I made it to an O'reillys parking lot and in the morning purchased a battery and an alternator as both tested to be completely dead. I believe the alternator is the original Denso, so I decided to keep it rather than trade it in for core. Anyways, truck fired right up and we made it the rest of the 450 or so miles home. On the way home voltmeter continued to bounce around.

I am no electrical guru so any help would be appreciated. Research on the forums so far tells me it could be the voltage regulator, or the CPS, bad grounding. Has any body had similar issues? any good advice?

Thanks!

Truck is a 1993 4x4.

What you described is alternator fielding failure, which could be the alternator field or brushes, the voltage regulator, (which is build into the PCM), the field power supply which comes from the ASD relay, or any of the wiring involved in all that.

Being the alternator tested completely dead, it's a good bet the original problem was alternator brushes. Odds are 10 to 1 the new alternator is defective. Otherwise it could be any of the other above things.

If the voltage dives and the overdrive stays engaged, it's not the CPS, and not likely the PCM.

JMartin is right on, another thing to check is the condition of the PCM to Connector pins, take it off and inspect for corrosion.

Thanks guys!

Sounds like the CPS is ruled out because overdrive stays engaged. Drove the truck today without issue, charging system seemed to be working just find. I'm thinking it must be a weak connection because of on and off it is. I'm terrible with this electrical diagnostics stuff. Thanks again!

The main classic "weak connection" is the slip ring and brush parts in the alternator. If they're poorly finished, they'll be erratic when they are new, settle down for awhile but wear fast, then fail again.

Morale of the story is keep your receipts.

The other take is DIY. If you have a good alternator that's run for years, and it quits, it's likely just worn out brushes. For a few dollars in parts, and an hour on the bench, you can hand polish the slip rings, install new brushes, and maybe a new bearing or 2, and have an alternator that'll run another bunch of years.

Where, pray tell, does one procure these new brushes ?

I have several of these dead soldiers laying around, as I have been replacing them with 110-555 Leece-Neville as time/money allows; but, it would be nice to have a spare ND or two around for quick fixes when I don't have the time/money to do the Leece-Neville conversion. (I also have a few new 110-555 laying under the bench; what I usually don't have is the odd length belt required after the swap.)


Thanks.