Is this likely the alternator?

[AGiorgianni]

Sorry folks if I'm posting this in the wrong forum. I'm not really sure where to post. Please advise if there is a better place.

Having an issue with my 92 xlt 108,000 miles. Here it is (I've also posted on rec.auto.makers.ford.explorer. Don't think there's a way to cross post:


I shut off my 92 XLT this morning and it wouldn't restart. Minor lights
go on, but when I turn the key to the "On" position everything goes
dead or almost dead. And of course it won't start on it's own


I jumped it with my portable jumper, and it started several times. So
I thought it was the battery, which is really old. I see a code J9 on
this DieHard. That, believe it or not, tells me October 1999. And I
checked my owners manual, and sure enough it shows my last battery
replacement 50,000 miles ago, in January 1999! That's a lot of time
for one battery. So I removed the battery and used my voltmeter. It's
showing about 12 volts with no load.

So I jumped it again and started off for the shop. But I noticed that
the alternator gauge is steady sometimes and then starts to jump
around as I'm driving steadily. Seems to me a worn battery would not
make the gauge do that. Is that right, or could that be the battery?
Cables were tight with no visible corrosion. No apparent problem with
the drive belt. Is that likely the alternator? Regulator is part of
the alternator on the Explorer, no? Any other possibilities? Could it
simply be the battery.

Additional info: I put the battery back and jumped it again. The voltage across the battery terminals when it's idling is 14 volts dead on with no variation, the same with lights off and on. If I shut off the eninge, the lights almost dim to nothing. So the battery was being charged but apparently not charging. I'm now thinking this is a catasthropic and sudden failure of this 10-year-old battery?


Thanks.


Anthony Giorgianni

 

[AccordRanger]

Try starting it then disconnecting the negative cable. If the alt is good it should keep running.

 

[AGiorgianni]

Thanks for the reply AccordRanger. It did stall a couple of times, but only when I was backing up with the bad battery and the alternator output dropped momentarily as I worked the clutch.

I just now replaced the battery, which needed replacing anyway, and drove a few blocks. Everythign looks sure and steady. Had to paint the battery tray, which was rusting, so it took me a couple of days waiting for the paint to dry, the reason why my reply is so late.

So just a battery.

Thanks again.

 

[mrboyle]

Very common for a battery with shorted plated to cause the problems you were experiencing.

 

[mrboyle]

Try starting it then disconnecting the negative cable. If the alt is good it should keep running.

This is not recomended on a computer controlled vehicle. It may work, but you run a serious risk of damaging some expensive electronics.

 

[AGiorgianni]

Thx Mrboyle

Good to know, Mrboyle. That explains it all.

Anthony Giorgianni

 

[SoNic67]

The true test is measuring the voltage with the engine running. It should be in the 14.4-14.8V range if the alternator is good. Slight variations in this range will be with the RPM's and full lights on.

 

[Heavymentill]

Check your battery with a hydrometer. You can get a cheap one in the $5 to $10 range. Also most parts stores will test your alternator for free. (auto zone)