jheis

Recently the battery died in my '82. I thought the battery was fairly new, but when I checked the lift out dots, turns out it was 2 months shy of it's eighth birthday.

Stuck in a new Interstate & everything was fine.

Took a drive yesterday and noticed that the voltage gauge was pegged - at the bottom! Same thing today - doesn't budge if I rev it up (but does flicker slightly with the turn signal.) Figured my alternator had died (sheese, seems like I just had it rebuilt - but the receipt says it was done in '99.) DVM reading about 12.5 volts across the battery with the engine off. With the engine running I was reading less than 12 volts from the underhood + terminal. Was planning on pulling the alternator this week end.

Anyway, hopped in the car for a run to the P.O. this evening, and every thing was back to normal with the voltage gauge reading around 13v (increasing with revolutions.)

Does this sound like an alternator problem or an intermitent problem with the voltage gauge circuit? Don't know if this was connected with the recent demise of my battery or not. I think I would have noticed the gauge pinned to the bottom of the scale.

Anyone BTDT?

James

ceedee

i might have an older style alternator i can sell you

jheis

Thanks ceedee, but not quite the answer I was looking for.

James

Dangerm

I've had some similar problems - earth problems with the guage

Alan

Well the DVM is the telling item. You obviouslty had a charging problem at that time and its obviously intermittent

... I'd check connections all round but particularly at the alternator. When it is charging what voltage is it charging at ? and does it still seems to be cutting in & out?

Alan

SharkSkin

Check the 14-pin connector, the Alternator exciter wire goes through there. Check the connection at the back of the alternator as well. The next time this happens, turn the key off then back to on -- if the charge light does not illuminate there is an issue with that circuit.

jheis

Dave:

The 14 pin connector you're talking about -- is that the electical part on the back of the ignition switch?

As far as I know, this has only happened once, but the only indication was the needle pinned at the bottom of the gauge & I think I would have noticed that.

James

SharkSkin

James, I'm referring to the connector adjacent to the jump post in the engine bay. The wire that commands the alternator to charge goes through there, and it's a likely corrosion/bad connection spot. The only other connectors on that circuit are in the CE panel and the edge connector on the instrument cluster. I'm thinking connector since the problem is intermittent. Ceedee just hat a problem that seemed to be the exciter wire terminal on the alternator itself being loose, making for a flakey internal connection.

Of course, it could be the voltage gauge too. IIRC that circuit powers other gauges too... so it would have to be the gauge itself(I think -- have to check tonight) or you would see other gauges acting weird.

jheis

Just tried my car again and it's back to the no-charge condition. Reading about 11.7 volts at the underhood + terminal with the engine running (brand new battery). Alternator light is not coming on.

Per Dave's suggestion, I pulled the 14 pin connector apart -- looked pretty good, but shot it with contact cleaner and shined everything up just in case. No difference, so it looks like I'm going to be getting dirty chasing my tail this weekend...

James

zoltan944

jack up the driver front of your car and measure at the terminal.

blown 87

Worn brushes will come and go like that.

docmirror

Yep, as with others I'm betting on the field circuit. this is the 'exciter' that makes the alternator actually start the charging process. No field voltage, no charge. Then, the brushes will make momentary contact with the field of the alternator and it magically fixes itself for a while. If not brushes on the alt, chase back from the 14 pin in the right side to pins H7 and H8 on central electrics board. Should be good 14VDC when the car is running.

Also look for a good size jumper between Z1 and Z6 on CEB, and check for 14V there. If you really want to give it a good test, carefully run a jumper from the D+ terminal on the alternator to the jump lug under the hood. When you start the car, the voltage at the batt should go to 14V very quickly. Be careful, your handling hot voltage at this point, don't ground it.

Doc

SharkSkin

That's a good point. My Ramcharger alternator doesn't charge for the first 15 minutes of running after I let it sit for a couple weeks, after that it's fine(gotta get in there and clean the brushes/sliprings).

James, are you driving your shark often enough to keep it happy?

jheis

Yup, it's my daily driver. (Of course, working out of a home office - I don't drive every day!)

Probably gets about 5-7k per year. 'Bout 120k on it now. Just checked and the alternator has about 40k on it since it was completely rebuilt.

James

SharkSkin

Does the alternator light come on when you first turn the key, before starting? If not, the bulb may be burned, causing your problem. Without that circuit, the alternator may or may not charge, depending on RPM, its mood, etc.