Potential Issues if a Demco Air Force One Braking System is Engaging the Parking Brake on a Sierra

Published 03/17/2023

Question:

I installed the Air Force One with remote monitor, light wiring kit and Blue Ox base plates on my 2023 GMC Sierra 1500. When I follow GM directions for flat tow, including disconnecting the negative cable with a knife switch, all appears good until I start to tow and the rear wheels on the truck lock and I find that the park brake has set. I removed the coiled cable connecting the RV and the toad for lighting and battery charge and everything works fine except I don’t have brake, signal lights or battery charge.

asked by: Ray H

Helpful Expert Reply:

I have not come across this being an issue when using the Demco Air Force One Supplemental Braking System # SM99243 in your 2023 GMC Sierra 1500 before.

So I went ahead and reached out to the manufacturer to see if they have come across this before and I have included what they were able to tell me below.

"It sounds like when the customer disconnects the negative cable, the truck is still finding a ground through either the tow bar or lighting cables. As a result the truck acts as if the battery is still connected and will engage the emergency brake when rolling as a safety feature. The lighting cable being the culprit makes sense as everything works properly when that is disconnected.

Other possibilities are that the battery isn’t getting disconnected correctly or the pickup isn’t getting put into neutral tow correctly."

They also mentioned that the work around for this would be to disconnect the positive side of the battery opposed to the negative side.

expert reply by: Scott S