'66 D 100 not charging

[Caleb]

ok heres the deal. my alternator stopped charging. the gauge reads a little left of the center at idle, when you turn on lights/wipers/etc. it goes all the way over to "D". And when you rev it up the gauge never gets past the center into the charge side. i replaced the alternator and regulator, made sure the fuse is good, and made sure all the wiring is good. Now heres the kicker--when i put the new alternator/regulator on, i started the truck and the gauge jumped all the way over to the charge side and stayed there for 45 sec-1 minute. then the gauge went right back over the the "D" side and i was back to where i started--with the brand new alternator/regulator not doing squat. what am i missing?

[cowboy]

caleb. to the site , have you double checked your ground & /or have the alt & V reg double checked , I have seen them do this & be bad from the start , even though there new

[PowerMan]

I've heard that it is also a good idea to change the amp gauge itself. My truck isn't charging either so we arew going to replace the gauge this weekend.

Power Man

[wideblock]

you have a short somewhere in the system. what happened was the new alt/reg combo sensed the short as a drian, so they went full tilt to "charge" the system. staying there as long as it did fryed the new reg. i only say this because i went thru the same exact thing on my 66. turned out to be old trailer wireing, hot wire was grounding to the frame and causeing the reg to try and over charge the system. fryed 3 regs before i figured this out. if you wanna run a fast check, disconnect the battery + cable and hook a test light between the connector and the + battery terminal. if it lights up, you got a drain in the system. pull one fuse at a time till the light goes out, then start tracing that circuit for the drain. if the light never goes out, and you got all the fuses out, then start tracing the circuts that arent going thru the box like radio, cigar lighter, trailer lights, etc etc.

[Jeffc]

1) sounds like the gauge is just fine,
it would not move if bad.
2) could be a bad ground, check engine
to battery ground and engine to fire wall
ground (cables all need to be good!!
and contact points clean)
3) rest of the system needs checked,the easy way is to take it to a parts store and ask them to do a charge
system test, most of the time it is free
in hopes of selling parts (assuming you can charge the battery to get it there).
Anyone of these could be bad:
alt, reg and battery (yes, even new ones).....
plus,
wire from reg to alt field wire, pulled off the
alt it needs to read 12v (or same voltage as battery)
with the key 'on'.

Be sure your field wire is good (wire from
reg to alt) I have seen these not work right
after they get hot from engine heat.

Be sure there is some charge in the battery
before hooking up a new alt, not doing this
can 'kill' a new alt real fast....

[Caleb]

thanks everyone for your help i appreciate it. it turned out to be a bad regulator so i replaced it and it charges great now. but again thanks for the input.