wont crank
 

how yall doing i have a 93 ram 350 dually 1gen 12 valve. Daily driver im a rig welder been cranking
and running fine had some cold temps below freezing. didnt bother pluging
in so not two days ago i get home kill the truck. i had couple days off so truck was sitting
so i plugged in the heater cause they were calling for temps down in lower twentys mind
u im in texas.my truck sat didnt try cranking it till late yesterday it did nothing like
the battery was dead so o thought ill just jump it off
that plan didnt work.so today i went and got another battery off my other truck and tried
charging the on that was on.my truck. i have been most of the day volt meter reads 14.5 volts on battery
then drops to eight .so my first thought id bad battery. ut heres the kicker
when i go yo turn the key to see the volt meter iy bottoms out and clicks and i can mess with the wires under the hood right on top of fender the relays. the volts jump up go to crank same thing again.
any help would be greatly appreciated thanks Roy