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
more information >
Featured Help Information
Instructions
Continue Researching
- Shop: Base Plate for Tow Bar
- Shop: Roadmaster Direct-Connect Base Plate Kit - Removable Arms
- Search Results: vehicle tow bar wiring
- Search Results: remote battery disconnect
- Search Results: trailer wiring
- Search Results: battery disconnect
- Video: Feature Review Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector-C47RV
- Video: Roadmaster Automatic Battery Disconnect Review
- Shop: Vehicle Tow Bar Wiring
- Shop: Trailer Wiring
- Shop: Roadmaster Battery Charge Line Kit for Motorhomes
- Shop: Replacement Roadmaster Smart Diode for LED Tail Lights - Qty 1
- Shop: Roadmaster Falcon 2 Tow Bar - RV Mount - 2" Hitch - 6,000 lbs
- Shop: Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector
- Shop: Blue Ox Base Plate Kit - Removable Arms
- Shop: Blue Ox Battery Disconnect for Towed Vehicle w/ Flat Tow Brake System - Gas or Diesel
- Search Results: blue ox rock guard
- Video: An In-Depth Look at the Roadmaster Diode 7-Wire to 6-Wire Flexo-Coil Wiring Kit
- Article: Trailer Wiring Diagrams
- Q&A: What is the Difference Between a Class II and a Class III Hitch?
- Search Results: trailer hitch
- Shop: Trailer Hitch
- Q&A: What is the Difference Between a 4-Way and 7-Way Trailer Connector
- Search Results: base plate for tow bar
- Article: Brake Controller 7- and 4-Way Installation Kit (ETBC7)
- Video: An In-Depth Look at the Roadmaster Battery Charge Line Kit for Towed Vehicles
- Q&A: Which is Better Roadmaster or Blue Ox Tow Bar
- Video: Comparing Portable Flat Tow Braking Systems - Curt RVi and Blue Ox Patriot
- Article: How to Measure for Trailer Hitch Drop
- Article: Wiring Trailer Lights with a 7-Way Plug (It's Easier Than You Think)
on Accessories and Parts
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.