On my 78 dodge ramcharger I have an issue, when I check it with a volt meter on the battery I'm getting 15.25 volts. These are some thing that I've done to the truck, did the MAD upgrade that bypasses the amp gauge, new battery cables, soddered and replaced the feild wires that looked alittle nasty and cracked and it's still reading the same. I also looked for any other wires that my be grounding out on somthing and I cant find a thing. If any one has any ideas please help me. I've got my truck with me at work today and will check it where ever you need me to with the volt meter, I'm just not that hot when it comes to figuring electrical issues.

One more thing that I wanted to add was that I replace the voltage regulator with a new one and it have the same readings of alittle over 15volts. I had another one that was used and it gave me a reading of over 18 volts so I stuck the new one back on it. I checked my brothers cuda to make sure my volt meter was working right and his is reading perfect right 13.8.

Read the voltage on the blue wire going into the ballast resistor & read the voltage there.... That is tied directly to blue wire going into the voltage regulator which is the reference voltage to the system & if it's low the alternator output is turned up to compensate...

In my case would it be this green one?

I wouldn't worry too much about an extra 1-1.5 volts, everything is designed for 14-14.5 volts with engine running. Lot of guys running 16v systems too, on race cars with minimal changes to the whole system.

Also, try another volt meter. I had a volt gauge that was reading 16v at RPMs, but a quality volt meter showed 14.5 at the battery, alternator and the VR.

What you are experiencing is high resistance in the curcuit somewhere. If I were you I would start cleaning all your connections such as the Ballast resister. By the looks of that bottom connector it appears that some heat may have been generated at that connection. Also clean all you connections at the bulkhead. We have all experienced this problem before. I ended up pulling all the wireing in the engine bay and going over it until i found a corroded ballast resister connection.

It does look to have gotten hot at one time. I checked the wire and look decent and not burnt. I'll try to clean them up some with some scotch brite or put new clips on it.

I'm getting areading of 14.70 at the green wire where it clips to the ballast resistor if that means any thing. Where's a good place to measure it before the ballast? Just stab it into the green wire any where before the ballast connection?

If your gonna stab a wire I'd stab the one going to the regulator... Unplug the regulator & verify the voltage first then get a number with the regulator plugged in & the engine running... Also regulator ground quality can be an issue....

With accesories on and truck not running I'm getting
12.44 at the battery
12.09 at the red wire on the alt
12.07 at the green wire on the alt
12.43 at the black wire wire on the alt

at the voltage regulator plug not running with accesories on
12.12 at the green
12.09 at the red

Now with the truck running
11.33 green wire at alt
14.6 red wire at alt
15.29 black wire at alt
15.09 battery

Still need to read the volts at the voltage regulator when running. I will have it in just a minute.

What voltage do you read if put one probe on the battery + terminal, and the other on the blue lead to the alternator? You should get almost nothing, but it looks like you'll see a volt or two.

Like mentioned above, you have a pretty good resistance drop through the harness causing the alt to overcharge its output. I installed a relay to get battery voltage to the regulator and avoid any drops along the way to fix my overcharging issue.

Sounds like you found the problem

In the picture below, the red arrows should be at the same voltage. It looks like you're seeing 1 to 1.5v difference. This is from too much resistance in the blue line. This causes the regulator to make the output at the alternator to be 1 to 1.5v higher, which pushes the battery voltage that much higher as well.

The solution is to either clean every connection in the blue loop (sometimes works, didn't for me), or the best solution, is to install a relay in place of the brown line to jump battery voltage directly to the regulator and alternator. The relay is turned on by the ignition switch. This bypasses all of the voltage drops.

need to have the truck running a fast idle w lights/heater on. It's a charging prob so need to duplicate the actual conditions where it's acting up. Bottom line is what charging voltage are you getting at the batt posts & not too much (overcharging) and not too little (eng wont crank). Assuming batt is good. Might make up some jumper wires w alligator clips on each end & jump each connection till you find the one that makes the charging voltage go back to normal ~13.8-14.2. Batt positive post to (1) blue wire alt male field terminal (2) top VR terminal in the triangle. (A) Green wire male alt field terminal to "side" terminal in VR triangle (B) alt case to batt negative terminal (C) v reg case to batt neg post (D) eng block to firewall (E) firewall to batt neg post. The black bulkhead connector is a frequent culprit and as said & from your posted readings the blue wire sense circuit is showing too low which is making the VR tell the alt to up the rate to fix it.

the plug going to the voltage reg. goes bad and will make it over charge.they sell the plug at napa.just a thought. brad