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.

I'm not much good on the electrical stuff, but I would like to welcome you to the board.:D

Welcome to the board and post a pic of your K5 when you can.

For your question, post it over here (http://67-72chevytrucks.com/vboard/forumdisplay.php?s=&daysprune=&f=64) and you are more likely to get more knowledgeable responses - I for one can figure out simple electrical stuff, but am pretty clueless on electrical issues.

:welcome2: From West TN :hi2:

Can you take the alt back and upgrade it to a "one wire"?

:agree: If you get a one wire alt you can bypass that external reg. Plus you can get a high amp alt if you switch to a one wire type. Use like a 8gage wire strait from the alt to your batt.

You may have a bad ground or a loose wire so I would double check all your connections and clean the plugs/connecters. Spin up the RPMs to about 1200 and check the voltage at the alt charge wire on the alt..should be up in the 14v area if it is but your batt is still at 12 then you know the regulator or the wires are bad or open...
Good luck

Thanks for the help guys. I ended up going with a one wire alt, and its working fine.