Jake53,
I always recommend buying a inexpensive VOM meter from your local hardware store. This meter will read AC/DC volts, resistance, and other values, depending on the meter.
Read the battery voltage with the rig off..then start the truck and bring the RPM up gradually. You should see the voltage climb to about 7.5 volts if everything is working. You will want to see a difference between voltage with the rig off and voltage with the truck running at a mid RPM.
You can do a rough test at night...start the truck, turn the light on, and as you bring the RPM up, your lights should get somewhat brighter. This will at least tell you that your GEN is GEN-ING!
When you start the truck, look at the ammeter at an idle. It will probably be centered...rev the engine up..if it swings over to discharge , it probably is as you have surmised..connected
backwards (to your new polarity) and is actually charging.
These are tough systems. Substituting a 12 volt for a 6 volt is truly a test of this system.
Maybe a old GMC fellow was the previous owner of the truck, and got confused when he installed a new battery..it sounds like you have a parade deadline, so grab a meter and cross your fingers!
Stuart
