Roadmaster Battery Disconnect Drawing Constant Power

Question

Question:

Hi, I just ordered a RoadMaster Battery Disconnect relay for gas cars. My observation is that this need power to stay on For the car to work normally. When my wife park the car in the garage, this solenoid is pulling 2.8A from the battery. That means that the car will be discharged in a couple of days. Is this correct understanding / expectation?

asked by: Jone O

0

Expert Reply:

Thanks for reaching out Jone. With the Roadmaster Battery Disconnect # RM-766, the dash switch only sends a momentary signal to change the solenoid between the connected and disconnected positions. Once the solenoid changes position, it mechanically stays there and does not require continuous power to keep the battery connected. Because of that, a continuous 2.8-amp draw would not be normal for the battery disconnect itself.

If you're measuring 2.8 amps while the vehicle is parked, there are a couple of possibilities. The measurement may be picking up the vehicle's normal electrical loads before all of its modules have gone to sleep, or there could be a wiring issue causing the Roadmaster solenoid's control circuit to remain energized.

A good first test would be to place the disconnect in its normal battery-connected/drive position, shut the vehicle off, and allow enough time for the vehicle's electronics to go to sleep. Then check for current specifically through the small control wiring going to the Roadmaster solenoid. You should not see a continuous 2.8-amp draw through that control circuit.

Where exactly are you measuring the 2.8 amps on the solenoid?

expert reply by: Christopher H

0

Rob G.

9/2/2026

My Jeep has this battery disconnect. It sits in the garage for month at a time without being cranked and I've seen no battery drainage over the past year. This disconnect has worked flawlessly for my flat towing.

Christopher H.

9/2/2026

@RobG Appreciate you hopping in here and sharing your experience!

John M.

9/2/2026

I also use this switch with no battery discharge. Has work flawlessly.

Christopher H.

9/2/2026

@JohnM Appreciate you sharing!

Charles

9/2/2026

I have used the disconnect for over two years with no battery discharge.

Christopher H.

9/2/2026

@Charles Appreciate the insight. What vehicle do you have this installed on?

Charles

9/2/2026

Ford Fiesta hatchback.

Christopher H.

9/2/2026

@Charles Thank you. Appreciate you getting back to me!

Henry W.

9/2/2026

Etrailer installed the battery disconnect along with the air force break system and the roadster tow bar in my Cadillac Escalade. They did a fabulous job and I couldn't be happier with the flat tow system and the Battery Disconnect. I NO ISSUES OR POWER DRAIN. My vehicle has many times sat for 1 month at a time without use and the cady starts up with out any issue. I am so very very happy with ETrailers installation. They are meticulous and could not have done a better job. The work clean and do their best to be precise.

Christopher H.

9/2/2026

@HenryW Really appreciate the kind words. Our installers are great and I will be sure to pass this along. Thanks for the feedback on your flat tow components and battery disconnect specifically.

Teuvo K.

9/2/2026

It should work without draining the battery, you have something else going on

Christopher H.

9/2/2026

@TeuvoK Thanks for your feedback here. I believe you are correct.

Roger S.

9/2/2026

The Roadmaster battery disconnect system is energized through a momentary action push button switch, in either state (connected or disconnected) there should be no current draw from the system. I have used two of these devices on various GMC Yukons I tow behind our motorhome, with no issue. However, I would stress the need to only use the switch for momentary operation of the solenoid, both to disconnect and reconnect the battery, there is an audible "click" when this occurs. It's not clear how you're measuring the 2.8A load, once you energize the system to disconnect everything on the vehicle should be completely dead. If the solenoid itself is pulling this current then maybe the solenoid has failed internally, causing a short. However, the only way that might happen is if the operating switch is providing a constant voltage, rather than a momentary energizing voltage, to operate the solenoid between states.

Christopher H.

9/4/2026

@RogerS Great information here! Really appreciate you hopping in.

Christopher H.

9/4/2026

@RogerS Great information here! Really appreciate you hopping in.

Mike P.

9/3/2026

I installed this disconnect on a 2020 Chevy Colorado and it has worked great. I haven't noticed any excess voltage draw or battery problems. The only issue is resetting the clock and there is a problem with android auto after it's used because it's on the positive side. To restart android auto you have to disconnect the negative or ground to reset. Could the solenoid be installed to disconnect the negative terminal?

Christopher H.

9/4/2026

@MikeP We've had this question before. Some vehicle manufacturers actually recommend disconnecting the negative terminal during flat towing however Roadmaster states their # RM-766 specifically needs to be routed to the positive terminal. They released a tech bulletin some time ago stating that if you disconnect your negative terminal you lose your tow vehicles main ground to the chassis. This then requires all of your flat towing accessories to be ground through the motorhome which is typically not going to be adequate.

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Roadmaster Battery Disconnect Drawing Constant Power

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