12 Volt power source for 939 Trucks

[bchauvette]

The heater blower motor switch has 12 volt for low speed you can tap off of on the 900 series trucks.

 

[hklvette]

The heater blower motor switch has 12 volt for low speed you can tap off of on the 900 series trucks.

Sort of true. That 12V tap comes from between the two batteries in series. If you use that method, it will consistently cause the "upper" battery to be over-charged

 

[bchauvette]

I figure that if the design engineers figure it is ok to feed a blower motor at half voltage it shouldn't hurt to power a GPS and/or charge your cell phone. There are several threads on running your own tap directly off the battery touting the liability . Another benifit of tapping off the switch is that it has its own protection. Not to say you shouldn't put lower rated fuses for your low amp aux circuit. Keep in mind if you use a cigarette lighter outlet configuration a lot of plugs, not all, have built in fuses.

 

[doghead]

It was a compromise by the engineers and they certainly did not provide it for additional accessories.

Bad idea.

 

[hklvette]

There's always this option: http://www.steelsoldiers.com/showthread.php?85317-M925A2-Delco-Style-Alternator It's what I'm considering doing to mine to deal with civy trailers.

 

[bchauvette]

Don't agree!!! what do you suppose the current draw for a 24v blower motor running at 12 volts? as the motor ages? Current draw for a GPS or Phone charger?, micro amps. insignificant additional load. Maybe a microscopic additional miss balance. Maybe you have to add water to the front batteries a very little bit more often or change the tap to the two back batteries once in a great while. If I had more load than a GPS and/or cell phone I would install a 12 volt alternator with its expense and work to install.

 

[swbradley1]

Butch, I would do either, I'd just use the 24v-12v converter from Pyle. $30 plus some wire.

 

[bchauvette]

Butch, I would do either, I'd just use the 24v-12v converter from Pyle. $30 plus some wire.

Above is an exact likeness of myself