How To Install Roadmaster Battery Disconnect On 2025 Buick Envista
Updated 02/27/2026 | Published 04/02/2025
Question:
2025 Buick envista can be flat towed with negative post disconnected. The blue ox and the roadmaster units you have disconnect the positive post. Is this acceptable since the owners manual says disconnect the negative post?
asked by: Jim
Expert Reply:
Hello Jim, thanks for reaching out. Battery disconnects like the Roadmaster Automatic Battery Disconnect, part # RM-766, do need to be installed on the positive side of the battery, even on vehicles that state to disconnect the negative cable.
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 enough 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. That is what the polarity of the solenoid is designed for.
Product Page this Question was Asked From
Roadmaster Battery Disconnect for Towed Vehicle w/ Flat Tow Brake System - Gas Only
- Accessories and Parts
- Flat Tow Wiring Harness
- Battery Disconnect
- Roadmaster
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Jesse M.
10/22/2025
Hey Jim, how did things go with the Roadmaster battery disconnect on your Envista? Did installing it on the positive side work out as expected? Your update could make it easier for others setting up a similar flat tow.