1955 B42 Model 12v Or 6v System ( Gas Engine)

[jcoll55]

Hi I have a 1955 B42 model Mack I am starting to restore. When I bought it. It came with no battery. I looked at the generator to see if it said what the volts were, it did not. So I pulled out a head light and it's a 6 volt light. But the wiring goes through a resitor before the light so it might be lowering the volts. the Battery box is small, only big enough for one battery, And It's hard to believe that one 6 volt battery could not only start a big gas engine but run the whole truck too. I hope some one might know what the deal is thanks.

[HK Trucking]

A 1955 B42 would have been 6 volt positive ground at time of manufacture.

It's anybody's guess what may have been changed or updated in the electrical system since then.

[Rob]

Hi I have a 1955 B42 model Mack I am starting to restore. When I bought it. It came with no battery. I looked at the generator to see if it said what the volts were, it did not. So I pulled out a head light and it's a 6 volt light. But the wiring goes through a resitor before the light so it might be lowering the volts. the Battery box is small, only big enough for one battery, And It's hard to believe that one 6 volt battery could not only start a big gas engine but run the whole truck too. I hope some one might know what the deal is thanks.

If you have a series resistor network in the headlamp circuit it is highly probable that the system has been converted to 12VDC. Why someone would go to the trouble of doing this to stay with a 35-40 watt incadescent lamp I will not understand but it wasn't my truck. 12VDC automotive headlamps are 50-55 watt and the lumen output is much higher. At less than $10.00 a bulb, they are inexpensive.

I would look further to verify the correct voltage of the system. On the firewall will be the voltage regulator. It is a black steel case and may still say "Delco-Remy" on the cover but it will be about 3 inches tall, and about 5 inches in length and have four, or five wire attached to terminals. One of the terminals will be stamped with the operating voltage, and a +, or a - indicating ground polarity.

I would look there, the magnetic switch that pulls the starter motor in, the tailamp bulbs, the interior dome lamp bulbs, and the dash lamps. There should also be a flasher unit either in the glove box, or affixed to the steering column, (or close proximity) that will have the operating voltage on it.

The battery only serves to start the engine, the generator carries the load at operating speed and recharges the battery. At low rpm such as idle, the battery does carry a good portion of the electrical load but as soon as the revolutions rise, the generator supplies the juice. Alternators do the same function at a much lower rpm.

Rob

[jcoll55]

Thanks for the reply's and the advice. It will be very helpful THANKS

[Greg Rider]

If it isn't 12v you should consider changing to 12 as things in life are much easier.

[vanscottbuilders]

Just my opinion, but -

I think the resistor you are referring to near the headlight may

actually be the junction block between the main wiring harness

and the headlight wiring harness. The original wiring harness

should consist of three sections; a main section, a cab section

and a front light section for lack of a better description.

Each section was connected via junction blocks.

Paul Van Scott