I have a 1978 Plymouth Trailduster. With the engine running I measure 18.4Vdc across the battery terminals. The Haynes manual says to replace the voltage regulator if the voltage is above approx. 13.5Vdc. I’ve changed the regulator twice which didn’t fix the problem. What do I do next?
Probably nothing. You didn’t have a problem. You were just checking it because you felt like it, right? “How good is the meter?” would be the question I could have in mind if it were my own. Then, how good a manual I had would be making me wonder. Then I would check one (electrical syatem) belonging to someone else.
The meter is good. I checked the voltage because the alternator guage in the dash pegged to the right.
Check the ground lead of the regulator. Sounds like the regulator is not grounded.
Along with checking the grounding to the regulator I recommend you also check the wiring to the regulator and make sure none of the wires running to it is open. The battery voltage sense wire may have a problem.
Warning: an overcharged battery can be dangerous
You may see acid (liquid) that boiled out…
It may smell like a rotten egg…
It may get hot…
It could explode!!!
If truly overcharged by voltage it would seriously damage it…
Any lead-acid battery system when overcharged will produce hydrogen gas. If the rate of overcharge is small, the vents of each cell allow the dissipation of the gas. However, on severe overcharge or if ventilation is inadequate, a flammable concentration of hydrogen may remain in the cell or in the battery enclosure. Any spark can cause an explosion, which will damage the battery and its surroundings and which will disperse acid into the surroundings. Car batteries should always be handled with proper protective equipment (goggles, overalls, gloves).
For a long time I thought the exploding battery was one of those tales about things that hardly ever happened. Then one night my son cranked his Ford Ranger and the battery exploded. Made quite a mess and put a big dent in the hood. Now I am a believer.
http://www.autozone.com/az/cds/en_us/0900823d/80/1e/98/04/0900823d801e9804/repairInfoPages.htm Use this wiring diagram to check for the correct voltages at the right places. When the link opens, click on Fig. 13.