alternator/regulator problems

[projectMANCHI]

so when my truck is at idle the alternator charges around 14 volts, which is normal id say, but the problem is when i turn on my blower and headlights it drops down and charges at like 12 volts

 

i think this is why I've been going through so many batteries recently :fs1: , any one have any ideas on why this happens? I'm thinking its a regulator issue or something along the lines, but knowing these trucks it could be a simple ground. 

 

any ideas or suggestions would be greatly appreciated, THANKS

 

(1986 2.5l 4 speed 4x4)

[desertmike]

Mine does the same thing. Always has, even since new. I checked the voltage at the battery and it was 14 something. The voltage to the gauge must get lost somewhere.