I've got a '71 ford custom w/305.The battery overcharges to the point where it boils the water out.The alt. & voltage reg. have gone out twice since this started.The back of the ammeter looks like it got real hot.It still works sometimes.Some days it overcharges and some days it works ok.Please tell me how to locate the problem. Thanks, James

NO ENGINE TOLD ! 2.0 OR 2.5LITER?????????
TH 8TH DIGIT OF YOUR VIN TELLS YOU WHICH ENGINE IS THERE, PLEASE TELL THAT FIRST.
The alternator is overcharging. what makes you think so?
a meter test.?
scan tool shows DTC that said that>?
OK JUST FLICKER,
lights flicker, what light, heads, or charge lamp error
or what? (i guess all)
putting in 3 wrong alternators is painful , there are 2 used, here. on 2 engines
one is pcm controls, other is not.
The 2 engines and matching ALTs:

DURATEC -VE 2.5LITER ONLY

ZETEC-VCT 2.0L ONLY

THEY ARE NOT THE SAME. ALT ! NOR ENGINES

DURA HAS 3 FUSES TO BLOW. BOTH ALTS USE THESE FUSES
F30-CJB. 7.5a, CENTERAL JUNCTION BOX.
and F2 =BJB, 15AMP BATTERY JUNC. BOX BJB
AND FB 175 AMP
THE REG IS INSIDE THE ALT HERE, NOT PCM

DID YOU REPLACE THE ALT WITH THE NEG LUG ATTACHED, IF YES, THE 175AMP FUSE IS BLOWN BOOM

ZETEC USES PCM REGULATION

AND SAME 3 FUSES TO FAIL, 1,2,3..

THE 175 FUSE MUST BE GOOD. TOO.

THE CORRECT GENERATOR FOR YOU ENGINE MUST BE USED
THE DURA and zetec alternator gens can NOT be mixed up here ever!

best way to buy any alt is by VIN # code or fail 1/2 the time or even 3times in row. or 175amp is blown
if buying over the counter (a new alt) tell them there 2 kinds used in 2000, tell them the vin 8th code.

Did you check the fluid in the battery. Level ok?
But the more worrying thing is the voltage regulator is not working properly anymore. Check the manual, to see at what voltage it should stop and measure if it does.

17v on is bad. its too high.
are you using a good voltmeter. a DMM, ? or relic analog meter.?
you put a new alternator in the car? not from autozoned i hope.
the wiring to the Alternator must be all good, them includes the case ground and battery cables, end to end, good and tight and not corroded.
the regulator is inside your ALT>
the ALT has 5 connections 1 is ground. any bad, reg can go nuts.
newer cars , go less nuts. they detect more errors and shut down
your is overcharging and will burn a battery up in no time.(heat)
wire:
Grounds good.
idiot lamp ,must be there, an working or alt may start up dead.
the lamp creates excitation currents, to boot up ALT.
wire B, goes to battery via fuse link, if this big wire fails. all bets off.
wire IG goes to 7.5A gage fuse, it must not be blown.
wire S, (sense) is 5amp ALT-s fuse, this senses battery voltage
if this wire drops in voltage the ALT will go to max. (or shut down)
toss coin there, lots of regs sub'd out in so many years, and rebuilts.

the regulator is not working right.
that means 3 things.
1: reg is bad.
2: reg is being lied to. (bad wires) even bad battery.

I would make sure the alternator is ok should be reading 14.4 volts at 1500r.p.m.'s make sure the drive belt to the alt. is tight

If you added any water to the battery I hope it was distilled water. Anyway if the battery is "boiling over" then I would inspect the charging system. It sounds like the battery is being overcharged by the alternator possibly caused by a failed voltage regulator. I wouldn't drive any more, as a severe overcharge can cause the battery to burst sending acid everywhere.

OK, I know I'm going to get a low score for this. but how can you tell if a battery is being overcharged? I'm not trying to be smart or anything. If you really believe it's being overcharged, I'd like to know more.

There is a fuse under the dash that is the same one that operates the fuel gauge, if it blows the alternator wont charge. If the fuses are good I would take the alternator off and get it tested. Hopefully the rebuilder will warranty it. I would also make sure the new regulator is compatible with the old type regulator system. Most large auto parts stores can test alternators, and they normally do it free.

Try starting the motor and then remove the negitive battery cable while running, If your car dies your alt. is bad. If your alt. was good it would be able to keep the engine running. Batteries are only for starting. If it stays running you might have a draw or short in the cars wiring and you would need a multi meter to check for draws. Or hate to say a shop. I hope this helps ya

Do you have an alternator with 2 field connections and one power output connection and a separate regulator?
If you do,with the engine running,remove the connection from the regulator and jump across the 2 connections in the wire harness,this will give you full field and the alt should show a charge,use a voltmeter on the battery and watch for an increase in voltage.If voltage increases,the regulator is bad or the reg ground is bad.(try cleaning the mounting bolt areas before replacing it)If no increase in voltage,remove the 2 field connections from the alt and ground one and apply battery voltage to the other with the engine running.You should see an increase in voltage if the alt is good.I am assuming you have battery voltage at the alt power output connection at all times?

put a new regulator on and dont use secondhand bits from scrapyard