g741.org

I took my truck out for about a half hour in the snow on Saturday. Truck has been sitting for a while and batteries didn't seem to have a full charge. I had the heater going, the lights, and driver's side wiper going the whole time. By the time I got home, the voltage meter was in the red. My truck has an alternator out of an M151, no generator. What could the problem be? A buddy of mine seems to think its because I had let the batteries sit without trickle charging them to keep them topped off, coupled with not having driven it enough to really start to charge it, and all that draw killed them. I don't remember ever having a discharge problem until after installing my heater. Maybe its wired wrong? Any advice appreciated.

BTw - my headlights were very dim when I parked the truck. Could my alt have gone south?

Sorry to hear of this, Nick. I had drainage issues too until I installed a kill switch-that seemed to cure my problem. How old are your batteries? If they've become sulfated from sitting discharged too long, you might need to replace them.
Gary

Batts are less than a year old(cheap Wal-Mart). I have a battery disconnect .........

Wouldn't hurt to check the alt output.

If you have a meter hook it up across the battery posts with the truck running. This will give you a quick check to see if the alternator is putting out. If you only get 24 volts its the alternator.

Sounds like you have the military volt meter (colored ranges). If the needle does not stay in the green above 2000 RPM with a full load then your regulator needs adjusting. If you connect a voltmeter (digital preferred) to the battery + post and any ground you should read 27 to 28.5 volts anytime the engine is above 2000 RPM with no load or full load.

If the alternator output is correct then the problem lies with your batteries and/or their terminals.

My alternator is internally regulated. I have no clue if its eve nable to be adjusted.

One battery is probably low, or has a bad connection. This may have caused a imbalance that blew out the regulator. Especially where you where using alot of accessory's, making a big draw on the system.

As long as the batteries are connected in series (even if the connections are poor) the batteries are recognized as a single unit by the regulator.

Nick, The ball is in your court. We need to know the voltage output of your alternator at over 2000 RPM. This means you'll need to get a volt meter. Connect the + red lead to the the + terminal (24 volt terminal) of the battery set and the - black lead to ground and run the truck at about 2000 RPM and tell us what the voltage reads.

Also you need to give us the make and model of your alternator so we can find the specs you need to work with.

GOOD MORNING, FIRTST THINGS FIRST, AS STATED ABOVE, GET A DIGITAL VOLTMETER; CHECK THE BATTERY VOLTS WITH THE ENG OFF. CHECK AGROSS THE LEADS THAT LEAD OUT OF THE BATTERY BOX. NEXT START THE ENG LET IT IDLE FOR A BIT, REV IT UP AND CHECK THE BATTERY VOLTS AGAIN, WHILE AT A HIGH RPM. IT SHOULD BE, AS NOTED ABOVE AROUND THE UPPER 27 RANGE. YOU COULD DO THE SAME THING WITH THE ONBOARD VOLT METER, THE ONE IN THE DASH, TURN ON THE DASH BOARD SWITCH AND NOTE WHERE THE NEDDLE IS. NOW START IT UP AND REV IT UP, DOES THE NEDDLE MOVE UP?? IF NOT REPLACE THE ALTERNATOR.

I have a voltmeter. Its analog though, which I don't think matters...I will do the test soon. I just haven't had time to go into the garage the past few days. One day during my Xmas vacation, I'll get outside and see what I come up with and will let you know.

That analog voltmeter will work fine as long as you can accurately read the graduations for the needed DC volt scale on it.
I have a cheap one for the house and its hard as heck to read. It's more of a "Yup, there's power" then anything else.