Troubleshooting '89 302 Charging system

Hello,
This is on a 1989 F-150. The truck sits for a long time, probably over six weeks since it was last used. The battery light comes on, and the
(built in) voltmeter is lower than normal, but still in the "OK" range. If I put an analog meter across the terminals, the battery reads 12 when not running, and about 14 when "charging". I would guess that both of these numbers are on the low side of "OK". The truck starts and runs fine, but I don't want to really road test it. Battery is charged up, and it cranked and started fine after the six week vacation.
There is a relay next to the coil (on the left cylinder bank) that keeps on clicking after I shut down the truck, if I smack it it stops. Also, it seems like, when I first start it, maybe the AC is running regardless of switch position. I'm not sure, but if I turn the AC on just after startup, I don't here any difference (from inside the cab), but when I then turn it off it kind of "thunks" and gets quieter.
Does the light come on below a certain voltage (14.6, 14.9, ??). I'd think that 14+ volts would charge it up, is that not the case? As I mentioned, it sat for awhile before this happened. Should I be looking for corroded connectors, or what?
Thanks for any and all help,
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That's the problem with analog meters.. make sure the needle is zeroed, and compared the reading closely with another 'healthy' charging system. Also it matters WHEN you take the reading. If you just shut the truck off, reading will be higher... if battery had been low, running voltage may read lower.

That's confusing... do you mean you charged it up during... or that it stayed fine WITHOUT charging for six weeks?

Normal .. does that to exercise the compressor, oil to seals, etc.

I've seen two rebuilt alts, for same vintage applications, do the same thing with nothing wrong with the charging system. There's a good chance it's just a fault in the volt regulator light driver.
Are you handy? search google for my alternator refurb tip. Get a spare from a salvage yard.. cheap insurance
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Backyard Mechanic wrote:

It was about 12 before starting (after sitting for a day or so), and 14 when running.

It stayed up w/out charging for 6 weeks, cranked and started fine. In the winter I trickle charge it if it's going to sit too long, but I didn't do that this time (wasn't worried about it freezing). When I noticed the light, I put it back away and took another vehicle to work. My wife put a charger on it that day, but it read fully charged after about a minute. I repeated this a few days later, so the batttery appears fine.

It seems the volt meter (built in) is also lower than I remember it being.

Thanks, I'll look for it. I was looking for a troubleshooting procedure. I used to work at a parts counter. A guy would come in for a battery one day, an alternater the next week, and a voltage regulator a couple of days later (and often a 3rd battery before he was done). I don't want to be that guy! I'd guess there's a place I could disconnect the wiring harnes and measure in order to check out the alternator w/out the battery load (and any extra shorts).
I'll look for a better manual, but thought alt.trucks.ford might have the answer!
thanks,
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General rule of thumb, minimum charge voltage is 13.5 volts, max rate 14.5. some ricers manuals allow as high as 15.5, but they have short battery life. Full charged battery should read between 12.2 and 12.6 volts, each cell produces 2.1 volts, and there are 6 cells in a 12 volt battery. First thing to do is pull the battery and take it somewhere and have it load tested. When your sure the battery is good, and has a full charge then you can start checking other things. if the battery is pulling high amps from the alternater, the voltage readings can be a false low. A battery with sulfated plates will pull a load on a battery charger for a very short amount of time and then the charger will show a low or next to nothing charge rate giving the impresion the battery is charged fully.
Whitelightning
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"Hank" wrote

Which one?
http://www.autozone.com/images/cds/gif/medium/0900823d800a1874.gif
http://www.autozone.com/images/cds/gif/medium/0900823d800a2d1b.gif

Disconnect the battery with the engine running? (aka: the quickest way to fry the alternator, regulator, radio, ECU, and everything else electronic in the vehicle). I thought we'd warned enough folks on the newsgroup that nobody did that anymore. I guess not.
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MasterBlaster wrote:

I just smacked the round thing in front of both relays. I guess I rocked the assembly enough to make whichever one it was stop. I'll try again and feel/listen for which relay it is.

I figured I'd need to put some load across the terminals before I disconnected the alternator from the rest of the car. Hence the question. Back in the day, I seem to recall a standard load that we'd use to test them. It was a big box, about half as big as a battery. If we didn't have that (special tool #xyz) we'd just use another battery. I'd guess that modern systems are much easier to mess up, so I thought I'd ask first.
Thanks for the link to the picture, that's a useful resource.
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Well, then??... replace it.
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Backyard Mechanic wrote:

What is it?
And is it not supposed to do that? My Bronco II used to make all sorts of clicking and relay noises after you shut it down. At the time (early 80s) I was told that it was normal.
Thanks,

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wrote:

I have a 89 F150 and I don't have anything clicking there. I don't know what it is either. Sounds wrong to me.
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