Testing Alternator

Igla · 07-13-2013, 06:14 AM

I wanted to see if the alternator was the culprit for making my battery go bad. Had the wife rev the engine and maintain it at 2K RPMs. I got a reading of 14.7V at the battery terminals. Is this acceptable or would you replace the VR? Dempsey's book states that the range should be between 13.5 to 14.5 volts.

My Interstate battery that went bad, had no water in it when I pulled it. PO had it installed in 2003. Would this be the reason for the rotten egg smell and maybe the alternator is actually running fine?

Note: I tested it with a Harbor Freight multimeter.

pete3799 · pete3799's Garage

14.7 is on the high side.
I suspect it is spiking higher than that if you smell rotten eggs.
Was that reading with the old battery or the new?
Hook your volt meter up so you can monitor it while driving.

Igla · 07-13-2013, 07:06 AM

I plan on buying a Optima redtop battery after my last battery went dead. I have tested my alternator voltage output at several RPM levels and it consistently outputs 14.7 volts, which seems above the acceptable range of 13.5 to 14.5 volts. I've looked into the charging specs for the redtop and it states it's 13.0 to 15.0 volts, no amperage limit at the alternator. That being the case, shouldn't I be fine?

mark houghton · 07-13-2013, 12:43 PM

Quote:

Originally Posted by pete3799

14.7 is on the high side.
I suspect it is spiking higher than that if you smell rotten eggs.
Was that reading with the old battery or the new?
Hook your volt meter up so you can monitor it while driving.

Yes, do that. I too had the rotten egg smell as my VR died, but only after shutting her down after a drive...which allowed the VR to heat soak and start acting up. I would start her back up, and lo and behold rotten eggs. Hooked up a temporary VM in the cockpit and registered 17 volts or so.

Igla · 07-13-2013, 01:15 PM

Quote:

Originally Posted by mark houghton

Yes, do that. I too had the rotten egg smell as my VR died, but only after shutting her down after a drive...which allowed the VR to heat soak and start acting up. I would start her back up, and lo and behold rotten eggs. Hooked up a temporary VM in the cockpit and registered 17 volts or so.

Could you please tell me how to hook up a temporary VM in the cockpit?

mark houghton · 07-13-2013, 01:57 PM

I already had a hot wire that was used for something that I used to have hooked up to. You can run a wire from your fuse box up front, or what I did was to tap in to the cigarette lighter circuit beneath the dash if I recall. Or you can trace wires back to the starter switch and find one that's hot. Doesn't really matter, as long as it's hot when the engine is running. Then run a ground wire to any suitable nut/bolt that provides a good ground.

Or, maybe to make it simple, buy a cigarette lighter power plug (male, that will insert into your female lighter socket) and take your hot and ground from there.