Should Roadmaster Automatic Battery Disconnect be Installed on Positive or Negative Side of Battery

Published 08/07/2018

Question:

Should this be instled on positive or negative side of battery. My owner's manual says to disconnect the negative but I saw something from Roadmaster that this should be on the positive?

asked by: Jib

Expert Reply:

The Roadmaster Automatic Battery Disconnect, part # RM-766, does need to be installed on the positive side of the battery, even on vehicles that state to disconnect the negative cable.

Roadmaster released a tech bulletin about this which is probably what you read. The reason is because if you use the disconnect on the negative side you'll lose your towed vehicle's main ground to the chassis. This means that all of the accessories that need to operate on the toad must be grounded through the connection to the motorhome which is not going to be a good connection. The ground wire is too small of a gauge and the distance is too great to get a good ground.

So even though your manual states to disconnect the negative side you want to install the battery disconnect on the positive.

expert reply by: Charles S