jonh229

Stock '96 K1500 4wd. Occasionally the dash ammeter starts fluctuating, sometimes up to 19v. Happens day & night. I can get it to stop by trying the window defroster button, the heater on/off, the lights on/off. But I can't necessarily reproduce the symptoms with any of the electrical accessories.

The alternator is a rebuild from AC Delco 5 yrs ago. It tests good at Kragen Store.

I just put in a new battery. The battery drains while sitting undriven. I found the hood light remaining on so I removed it and recharged the low battery to 13.8v. Vehicle sitting for 4 days now and battery down to 13.1v, seems to be draining at rate of about 0.15v per day.

I still need to follow the battery ground wire to make sure it is ok.

I'd like to know if that much battery drain is normal or not. I have never bothered to check it in the past and know there is a parasitic drain but I don't know how much to expect.

Any other suggestions?

Thanks, jon

MDTAHOE

That is not much of a drain. You need to measure the drain in milliamps. Disconnect the negative cable, hook a meter between the cable and the battery. Record the drain in MA at 1 min, 5 min and 30min. Should be around 25Ma or less (.025a)

jonh229

MDTahoe:

Thanks. Unfortunately, I can't use the lowest scale on my ammeter because the interior courtesy & dome lights come on until the delay times out, drawing too much current for that scale.

Is there a way to defeat that courtesy timer so that I can use a more appropriate scale on my ammeter?

Jon

MDTAHOE

Take the bulbs out

RacerX

Kragens tested the alternator for output, right? They check for Amps, But not voltage. I think the internal voltage regulator is kaput.

jonh229

Interesting. How can I check this myself?

I did check the current draw, I get a steady 3.5ma over a period of more than an hour. I used a Fluke 77 for the reading, between the battery negative and the battery ground wire. I also checked it with an ancient analog multimeter, it showed ~ 3 ma.

Jon

RacerX

Well, its internal so you cant test it I dont think, but the sign is when the ammeter runs to 19v. That is not normal. When running you should be in the 13-14v range. If you get up to 16-19v you are overcharging the battery(which can lead to premature battery death, due to overheating and electrolytic gassing of the cells). In addition if your battery has those fancy vents on it the gas can creep out and cause some corrosive action on the battery tray.

But anyway your remedy for this excessive voltage of 19v is to use the high current load items in the car to draw it off, the defrost, headlights, and blower fan, but not the normal electrical accessories, radio, windows, wipers. I suspect the voltage regulator in the alt.

And for a 1996 I dont think a voltage of 13.1v is bad. Every battery I have is at 12.4-6v after sitting for few days and my cars are the same age with aftermarket radios.

jonh229

>But anyway your remedy for this excessive voltage of 19v is to use the high current load items in the car to draw it off, the defrost, headlights, and blower fan, but not the normal electrical accessories, radio, windows, wipers. I suspect the voltage regulator in the alt.

Just to be clear, the 19v is not steady. The dash meter (I incorrectly called it an ammeter, I meant voltmeter) starts bouncing around from a low of 12 and peaking at 19v. Running lights/heater in this condition results in flashing lights and the heater fan 'surging' as the voltage changes. This is an intermittent condition where it will run fine for 5-15 minutes then start acting up. Powering on/off accessories causes this condition to settle back to normal but it isn't long before it starts happening again.

Since the voltage regulator is diodes I figured that it was either good or bad, not something that produced an intermittent condition. I'll go ahead and swap out the alternator. It's only been 5 yrs since I put in the last rebuilt one. Oh well, guess that is the price of buying a rebuilt vs. new.

>And for a 1996 I dont think a voltage of 13.1v is bad. Every battery I have is at 12.4-6v after sitting for few days

Thanks, I have not kept track of actual voltages in the past so didn't know if that much loss was too much or not.

Jon

73shark

Rebuilt alternators are a crap shoot at best.

RacerX

Thats why you get the one with the lifetime warranty. As long as you own the car, it is under warranty.
There used to be a guy here who would rebuilt Alternators and Starters for like $60 but they bought him out and put a hair salon in his location.