How Does Automatic Battery Disconnect Work on 2016 GMC Sierra 1500 w/Negative Battery Cable Removed  

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Expert Reply:

The Roadmaster automatic battery disconnect # RM-766 has a switch that mounts inside the vehicle. Flip the switch and it automatically disconnects the battery power from the rest of the truck so you will not have to disconnect any battery cables. Roadmaster has determined the disconnect will work best on your truck by disconnecting the positive cable. You should not use # RM-766 on the negative battery cable on the newer Chevy or GMC trucks.

The battery power has to be removed for your 2016 GMC Sierra because the key has to be in a certain position to flat tow the truck. If the battery keeps supplying power to the truck and the key is left in that position there are components on the truck that will draw power and drain the truck battery. So you can either use the automatic disconnect or manually disconnect and reconnect the negative battery cable to prevent that from happening.

To keep a maintenance charge on the battery I recommend using a harness such as # BX88206 with the tow bar wiring you will be using so that you can run a wire from the connector at the front of the truck to the vehicle battery.

There are a couple of ways to do this. First, you can tap into the running light circuit in the tow bar wiring but to provide power to the battery the RV running lights would have to be on all the time. Or if the connector at the back of the RV has a working 12 volt circuit you could use that circuit instead.

Which ever way you choose you would just attach the wire to the appropriate corresponding pin at the back of the connector that will be at the front of the truck and the other end of that wire will go to the positive battery terminal.

expert reply by: Michael H

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