Electric

[Barra]

The wife just took the truck out. She reported that the voltmeter jumped around, and the battery light flickered. IT steadied out, but then the voltmeter steadily dropped to read about 12 volts. Then recovered back to reading the normal 14 and a bit. Aside from the obvious loose belt, loose bolts on the connections to alternator and batteries, any suggestions to check?

Cheers!
Barra

[tom.mcinerney]

What year/model/mileage? Alternator brushes eventually wear down, get intermittent. If lower miles, regulator may be fading. There's a fusible link in alternator output lead(to Batt+). Have battery cables and engine grounds been maintained?.
May help to check voltage at battery with digital voltmeter--it's possible that the instrument panel gauge has bad connection, or is the piece at fault.

[patrick m.]

My two year old "Delco" just did the same thing last week, started with a whining noise for a few days, then the volt guage started bouncing around during a trip home from work. The volt guage then came to rest well below the 14 mark and the batt lite came on (whining noise gone).
glad Delco has a "lifetime" warranty plan. :cool:

[Barra]

It's a 1995 k2500 Suburban. I recently had new alternator and batteries put in (November time frame).

A bit more info since it did its trick for me the other day...

The tach goes from reading correctly to zero and back again, voltage drops to battery. Apparently the tach is linked to the alternator in these things, and for some reason the alternator is flashing on and off. I checked connections to it, and traced the wiring harness back a short distance. No further troubles. I'm suspecting a loose connection in the wiring harness which is resulting in the alternator field flashing on and off.

Barra

[lupey6.5]

the tach is connected to the tach because there is no ignition coil to read from like a gas engine.you are in the right area with the alternator. it may be bad thats why they have a warranty. my truck eats an alt every other year and has eaten a cheap remanufactured unit in 4 months. check with the shop where you had the work done or the store you bought the parts through. many big name discount parts stores will test your charging system for free in about five min. to see what has gone bad.and sell you some parts...good luck

[tom.mcinerney]

Might want to do a "search" for 'alternator' or 'tachometer'. The tach is fed from one of the alternator leads(alternator output is 'pulsed...).
A few members havs experienced failure of relatively 'new' alternators....

[Beedee]

My alt died just last month, I took it to the local auto elct shop, dropped on the counter and the tech never even asked the prob, just said "Blown Rectifier". Asked me if I wanted to change it out myself or get them to do it, strapped for time so got them to do it, cost me $30.00 or something like that.
My thoughts are, if he never even tested the alt, is this a weak point?
$30.00 was a much better price then the $230.00 for a new one from GM. :D , (prices are Canadian)