when im at a stop and my heaters on full blast i go from 14 volts down to about 10. i just had my belt replaced, do you think the cause of this is maybe the belt is loose. if so, how can i check the tension?

 

to check your belt twist it you should be able to twist to a 90 degree angle any less to tight any more to loose also you may want to check your alternator if that doesnt help

 

I have fought this for a little while, i went through all the crap, new alternator, starter, battery cables, grounding straps, belt, new battery x2, plus a new headlight/ dimmer switch, it still drops it a little bit but the next thing to replace is the HVAC control, mine is a 1990 and I have been told by a couple people that there can actually been a bad ground or just plain worn out. Just some thoughts let me know if you get it figured out

 

i had a voltage drop in mine as well. traced it back to a bad connection on the alternator itself. if you replaced the alt i dont know what to tell you from there