ok so I had a problem with my voltage was not charging enough so swapped in a new bwd vr, was charging at 15-16v would not drop any lower.. cleaned grounds, grinded down to metal where the vr mounts still no change, so a budy pulls a vr off 1 of his parts trucks for me to install, she's charging at 14.6. I thought problem was fixed, go for a drive an my volt gauge pegs out at 18v, I thought ok maybe it was the aftermarket gauge, because it would hit 18 then drop down to 14. so I park the truck the next day I fire it up hook my multi meter to the battery an watch the volt gauge an my multi meter an both are dead right 17v then drop to 14v.. the alt is new maybe a month or 2 old. right now I yanked the engine wire harness out and am going through it, but ya guy's got any thing else or idea's??

The simple answer is both of the new regs could be bad. Might take voltage readings at all terminals/places & post what you get. Could swap in another alt from one of your other vehicles for a quick test in case its' field circuit is shorting out but you did say it was charging LOW & the prob really took a wrong turn when you started replacing regs. (what is a bvd reg?). This high voltage is at the alt not the batt correct? I'd take off all the field wires & with jumper wires with alligator clips I'd jump from the batt positive post (or starter relay batt stud) to either alt field & the "top" terminal on the reg and from the "side" reg terminal to the other alt field terminal and jump from the reg & alt cases to the batt neg post and from eng block to batt neg post. A 6 or 8 ga jumper from the batt positive terminal to the alt batt stud. Then see what you get for readings. gotta be either reg/wiring or terminals/alt. A bad/sulphated batt wants high voltage as it has a high resistance to being charged but as said it was LOW before the regs were changed. Holler how things turn out

I dont see what year it is but if it is the 2 wire electronic voltage regulator you need to make sure the 12 volt key on wire at the regulator is making good contact to the reg terminal. The reg if its the electronic one should have a triangle shape harness connector and it will have 2 wires in it. One is the ground for the alt field circuit and the other is the J2 circuit which is 12 volts at key on. If that 12 volts with the key on wire is not making contact with the reg terminal then the voltage reg wont know the charging system voltage and will keep the field wire grounded giving full charge thinking the battery is not up to the 14 to 15 volt cut off. The reg wont know what the voltage is so it will keep charging believeing the battery is still low. It needs to see the voltage so when it hits around 14.5 it will unground the field to keep it from overcharging. Also check the voltage at the alt output wire with the eng off not running as it should be about the same as the battery volts. Ron

Robert and Ron are correct. If reg and alternator are good, Bad connections and bad grounds are usually the cause of most voltage problems. Check all connections, the bulkhead connector, check all grounds, bat to block and to firewall/body. Make sure the regulator is grounded to the body, scrape the paint off if necessary. This grounding especially applies to the ECU if you have one.

i pulled the whole engine harness out, bought a new voltage reg conector, an am oing to go through an see if any wire's ect are cracked our fried..

I've seen this problem with a 74 Scamp I had.
It turned out that the wire feeding the voltage regulator is also the same one that supplies the field winding. there was a substantial voltage drop in that wire and the regulator was responding accordingly by upping the voltage. I ended up boiling the water out of the battery before I was able to track it down.
Mike