Just purchased a 72 K5 Blazer, and it turns out there is a charging issue. While the motor is running, I only read 12.5 volts on the system (freshly charged battery) opposed to a normal 14.2 volts. I have replaced the Alt, Reg, and it has a new battery. I am told that on the alt, the F term should read 12 volts when the ignition is on. Well, I'm not getting it. On the reg, I am only getting a 12 volt reading on the number 3 terminal which I understand is the cable running from the Alt to the battery. My guess is possibly the wire running from the ignition to the regulator? What are your thoughts. I appreciate any help. Thanks in advance.

internal or external regulator
if external did you polarize your regulator

Welcome to the board from West Michigan!

I would suggest not polarizing the regulator as serious damage could be caused.

I believe that you are on the right track as far as the voltage from the ignition. The actual voltage can be less then 12 volts but there should be a reading.

Do you have gauges or a light?

Jim

y

internal or external regulator
if external did you polarize your regulator

Regulator is external. I am not sure what you mean by "Polarize the regulator." Thanks for your help!

i'd say check and clean your grounds real good before going any further// from reg to core support, core support to frame batteryand engine to frame //jlots of people make the mistake of assuming that if they're in place that they are grounding!!! clean shiney metal to shiney metal is a good ground

Charging/starting system wires see alot of current and can wear out. It's not uncommon to see voltage drop to wires near starter, just due to age and heat abuse. I agree with checking the grounds first. Is the truck idling low?, does the voltage come up with RPM's ? Just trying to eliminate something for ya.

Thanks for the info guys. I'll re-check the ground wires. What are your thoughts of converting to an alternator with an internal regulator. Know of any sites with good procedures?

I do not have a solution but mine is doing some weird stuff too! It started charging at 17 volts just after another electrical problem(seems main power wire shorted to frame and burnt in two). I found the contacts in the regulator welded closed. replaced the regulator and now have to rev the engine to get it to start charging. once it starts it works fine you just have to rev it up a bit like 1500-2000 RPM's! Any Ideas?

SORRY ABOUT THE THREAD JUMPING!!! Just thought while we were brainstorming Alternator problems.

http://67-72chevytrucks.com/vboard/showthread.php?t=119379

http://www.chevelles.com/techref/tecref14.html

There are two types of generator and electromechanical voltage regulator combinations used with DC generators.

In an "A Circuit" system, the field is grounded through the regulator. "A Circuit" systems are found in most Ford and GM vehicles.

Most Chrysler vehicles had a "B Circuit" system which was grounded internally through the generator.

To polarize an "A Circuit" system, connect the FIELD, ARMATURE, and BATTERY leads to the regulator. Connect the battery. Then, momentarily connect a jumper wire between the ARMATURE terminal and the BATTERY terminal at the regulator.

To polarize a "B Circuit" system, connect the FIELD, and ARMATURE leads to the regulator. Connect the battery. Then, just before installing the BATTERY lead, momentarily touch it to the ARMATURE lead terminal.

he's got an altenator not a generator 2different animals
generator is a DC charging system
Altenator is an AC gharging system trying to polarize will cause damage to electrical system could fry the battery and cause burns to person attempting this futile endevour

While changing from an external regulated alternator to an internal regulator is a good thing to do, there is still the problem with no voltage from the ignition. Both external and internal alternators need power from the ignition to intiate the charging of the alternator.

It is very easy to convert and a quick search of the FAQ's should come up with the procedure for changing to the internally regulated alternator.

Jim

.

It is very easy to convert and a quick search of the FAQ's should come up with the procedure for changing to the internally regulated alternator.

Jim[/QUOTE]

The link is in my post above along with another one.

Thanks for the help guys. I ended up going with a 1 wire alt, and it's working fine.