Negative disconnect switch

[ZGjethro]

When I bought my 1952 truck, it had a disconnect on the negative cable. The switch recently failed and I bought a replacement. In the instructions, the maker said it should be installed on the positive cable. The switch can be used as a racing disconnect, so that is why the positive lead is specified. All my accessory wires are fused right at the batteries, and a positive cable disconnect will not help me. I am going to put the new switch in where the old one was. I basically want to shut off any return path in case something is left on. I mostly use it when the truck sits for a while. Is there anything I am overlooking?

[ZGjethro]

I just installed the new switch. If I leave the lights , added turn signals, or ignition on, the negative switch will turn them off. By turning the ignition off I mean the voltage gauge shuts off if the negative switch is turned off. Once the truck is running though, the negative switch will not shut the truck off. The only off is the ignition switch.

[MSeriesRebuild]

I just installed the new switch. If I leave the lights , added turn signals, or ignition on, the negative switch will turn them off. By turning the ignition off I mean the voltage gauge shuts off if the negative switch is turned off. Once the truck is running though, the negative switch will not shut the truck off. The only off is the ignition switch.

That is perfectly normal, the engine continues to run as power produced by the generator keeps current flow to the distributor even though the battery path is disconnected.

[ZGjethro]

Thanks Charles. I have this paranoia of running my batteries down and not being able to get a jump from any car on the road in my town, the truck being 24 volts. That is why I like the idea of the battery disconnect.

[cuz]

You can also carry a double set of jumper cables and be able to buddy up two 12 volt helpers for your 24 jump.

[Cal_Gary]

I also run a disconnect switch as a theft deterrent (although someone who really insisted on nabbing it would do so anyway).
Gary

[m15256]

Batteries wired in series will develop a condition where one will always take a higher charge, though the cumulative voltage of the two will control the voltage high cut out in the regulating system. This is true even if the batteries are "identical" and same age. Over time this can become quite pronounced and one way to manage the problem is to occasionally charge each separately on a 12 V charger. If you find that the engine will turn over and not quite catch you can #1 beat a dead horse and keep trying until the batteries are completely discharged or #2 have a passerby jump the battery with a 12V that you know historically is the weaker one. Alternately you can carry two sets of jumpers and jump both batteries at the same time or given enough time charge both (one at a time) off of one car by using their charging system. Their system does not need to be 24v. I worked on a ship that was wired for 120 V DC with (10) identical 12 V batteries in series and found quite a wide range of voltages between batteries after the system was fully charged to say 135V.
A disconnect switch that turns off ALL the current in an antique vehicle is a must.