I'm having a strange charging problem (I think)...

[gavio]

Recently I've noticed at night that my headlights seem to surge brighter and dimmer with engine speed. I check out my voltmeter (damn GM for not choosing an ammeter instead!) and surprisingly it reads HIGHER than usual - showing like 16 volts or so instead of the usual 13.

I also noticed that my belt has started squealing a lot (day or night) even though it SEEMS to be as tight as it was before. During the day, the voltage reads about like usual, maybe slightly higher.

Then, last night, I thought i detected a faint burning smell (hopefully I am imagining that part).

Other than that, it runs fine and seems about like normal. From inside the vehicle, I thought I heard a bit of a grinding sound at one point, but listening under the hood revealed nothing beyond the usual huge amount of general racket.

Oh, one other thing, when I checked it out while it was running, it seemed that the alternator belt was kind of jumpy, but as I mentioned, it is tight when checked with the engine off.

Any ideas what's going on here? This is your basic NA 6.2.

Thanks for any clues.

[britannic]

16V is too high, 14.75 is usually the absolute max - your batteries are in danger of being overcharged.

Sounds like your alternator's built in regulator is on it's way out. If your engine doesn't have the later year pulley damper, then the belt jump is part of the diesel's acceleration/deceleration as the pistons come up for compression (gasser's are much gentler since they have less than half the compression ratio).

[gavio]

So the solution is a rebuilt alternator, i suppose.

I believe the stock alternator is like 85 or 95 amps or something like that. Since I'm building in a camper setup and what not, I'd be interested in moving up to a higher output alternator. Anybody know where I can find a decent quality, higher output alternator that fits these engines for a decent price?

Thanks, Britannic, you can always be counted on for a useful answer. I had a feeling something was going wrong, but had been thrown by the high reading - I guess I would more have expected a low reading. Out of curiosity, can you explain why I'm seeing the higher voltage when the lights are on rather than when they are off?

Thanks.

[DmaxMaverick]

gavio

Get that thing fixed quick. Won't be long before you smell rotten eggs and destroy the batteries. Don't drive it unless you have to, and then turn EVERYTHING electrical on. Max blower, headlights, dome light, everything. It will minimize the damage by reducing the overcharge.

If the alternator seems mechanically sound, you can just buy the regulator and install it yourself (if you have a stock/early alternator). The shaft should turn quietly and easily with very slight play play at the pully. The regulator is about 3/8" thick, 1" wide and about 2" long, angled in the middle (working on a mental picture here). The regulator should cost no more than about $15 at Autozone, Kragen, etc. If you have the high output alternator (108 or 120 amp), it will be about $20. NAPA will be a couple bucks higher. Don't try the dealer. There used to be overhaul kits available, which came with the regulator, brushes and bearings. If you can get that, do it. That's about all you get with a rebuilt unit.

Replacement is simple with the alternator off the truck. I haven't done it in about 10 years, so bear with me....

Put a scribe mark (or use a Sharpie pen) between the halves of the housing so you can make sure you put it back together the same way. It will fit if the halves are rotated. remove the long bolts that run fore/aft, end to end. The alternator should separate at the seam in the middle. Take it apart and blow out the dust and clean as good as you can. The regulator is mounted in the rear half of the housing. It is the part that has the connectors you plug the wires into. Remove the bolts that hold it, and replace with the new one. If you have the bearings and brushes, replace them. Add a little high quality wheel bearing grease to the bearings. Pin back the brushes with tooth picks or straightened paper clips (or any similar device) through the holes in the rear housing around the bearing cup. Reassemble and remove the pins for the brushes. Tighten the bolts and it's good to go. Just like new.

The later alternators (post '88, or so) are a lot more difficult. The regulator is more integrated into the alternator and requires de-soldering, tweaking and soldering. The regulator is also more expensive at around $40.

Also, upgrading the alternator to the higher output is simple, but will require a new bracket. The 108/120 amp alternators are larger. The mounting holes are the same, but the housing is larger. The original adjustment bracked won't line up. You can "adjust" the bracked with some heat and bending, but they usually crack very soon. Best bet is to find one in a wrecking yard.

Just noticed you have a G20 van. You might already have the high output unit. Best thing to do is take the alternator out and match it up with one at the parts house to confirm which one you have. The high output has a housing about 1" larger diameter.

Good luck.

[gavio]

Wow, thanks for the major details!

I noticed today that the voltage was fluctuating much more than before even with the lights off, so it's parked until I fix it. Thanks for the warnings. As luck would have it, my roomate just left today for a week and I have access to her VW Passat turbodiesel, so I won't suffering TOO much!

Gavio