View Full Version : Alt showing 12 volts while car running

08-18-2009, 06:23 PM
I just tried replacing the alt with a junkyard alt basically, off a car with 70k miles, just to work temporarily and it works slightly better than my old one. Puts out power about 1600 rpm, old one didnt work until 4k rpms. Would a bad ground affect the batterys charging ability? I dont have too many grounding options, since everything else is bolted to something that gets up to 150-200 degrees and huge bolts. I just upgraded the factory ground locations with 4 gauge from 8 or 10 gauge. They were really rusty bolts though, none looked good to me, and i forget how to check resistance in a ground location. Any advice? I'm going to get a new alt tomorrow hopefully and test, although i'm going to try replacing the pigtail connector on this first

08-20-2009, 04:10 PM
Well The ground is def. a main part of a charging system.Do you have the exciter wire hooked up properly? Possibly the internal regulator is bad but Im not sure.An easy wat yo check ground resistance is with a dmm,put it on the setting that when you touch the pos and neg on the dmm together it beeps,touch the beginning of your ground with the pos and the end of the ground with the neg,if it beeps soild then you dont have a break in the wire,but thats just a ghetto way of doing it and isnt always accurate.

08-20-2009, 04:28 PM
I had got a bad alternator for my replacement, already had it swapped out. I believe something was grounding out in my replacement alternator, as the alternator smoked until the battery was down to 0 volts. On the side of the road no less, when i thought it was fixed, and didnt have any tools. Basically watched my battery die and hoped the car didnt catch on fire, which it didnt, it was just the alternator smoking, but had NO way to disconnect it. Just swapped my alternator for a motorcraft rebuilt one, i believe a 4g off a cobra, and its all better. I want to buy a high output alt though, i'm open to only a few different company though. The local people heard of ohio gen and told me to stay away from them, and the brands i'm interested in right now are mechman and DC Power. I'd look at other ones, but i've spoken to mechman a few times and hes taken good care of me, and Rob at DC seems to give amazing service as it shows on here from his loyal customers :p:. Anyone have any used alts, hit me up, otherwise i'll have to save up money for something brand new.

08-20-2009, 04:50 PM
you are asking for a used alt and you dont put what kind of car you have?

08-20-2009, 05:24 PM
you are asking for a used alt and you dont put what kind of car you have?

Oops. Its a 93 lincoln mark viii, currently using a 4g alternator off a 4.6 dohc cobra mustang for a little more power, old one was 3g.