Troubleshooting Voltage Drop from 12V to 7V When Trailer Brakes are Installed
Updated 03/17/2025 | Published 02/28/2020
Products Featured in This Question
Question:
I checked my brake wire coming from my truck all the way to where it connects to my magnets for my electric brakes. I have almost 12v until I hook the wires up for my brake magnets and it drops to 7v. What could be my problem with my brake controller turned all the way up to 10.
asked by: Alexander W
Expert Reply:
It sounds like you may have a poor ground connection which is causing low voltage when you are testing. Sometimes it may look like we have a really good ground point but some paint or debris is getting in the way and causing issues.
What I recommend doing is taking your trailer brake ground wires and running them up to your main trailer ground location. You will likely need more 10 Gauge Wire # 10-1-1 and I recommend using Heat Shrink Butt Connectors # DW05745-5 because they hold up much better than standard butt connectors in the elements.
If you are still having issues then you may need to route the ground wires into your trailer 7-Way (5 o'clock pin) and then from there up to your tow vehicle battery to ensure that you have a constant ground on that wire.
Let me know if you're still having issues and I can help assist you further.
Product Page this Question was Asked From
Dexter Electric Brake Assembly for 4 Bolt or 5 Bolt Flange - 12" - Left Hand - 6,000 lbs
- Accessories and Parts
- Trailer Brakes
- Electric Drum Brakes
- LH
- 6000 lbs
- Brake Assembly
- Manual Adjust
- 12 x 2 Inch Drum
- Dexter
more information >
Featured Help Information
Miscellaneous Media
Continue Researching
- Shop: Brake Controller
- Shop: Optronics Flexible LED Light Strip - Weatherproof - White - 17' Long
- Shop: Trailer Hitch
- Shop: Redarc Tow-Pro Liberty Brake Controller - Dash Knob - Up to 2 Axles - Proportional
- Shop: Redarc Tow-Pro Liberty Brake Controller w/ Universal Wiring Harness - Dash Knob - Proportional
- Shop: Redarc Tow-Pro Liberty Brake Controller w/ Custom Harness - Dash Knob - Up to 2 Axles - Proportional
- Shop: Coil SumoSprings Custom Helper Springs for Coil Spring Suspension - Front Axle
- Shop: Replacement Front Cover for Lippert Edge Awnings - Drive Head - Black
- Shop: etrailer Electric Trailer Brakes - Self-Adjusting - 10" - Left/Right Hand Assemblies - 3.5K
- Article: VCC Pickup and Dropoff
- Q&A: Troubleshooting Voltage Drop to Trailer Brake Assemblies
- Video: Making sure the Redarc Tow-Pro Liberty Brake Controller Fits
- Q&A: Self-Adjusting Trailer Brakes For a Lippert 4,400LB Axle On 2017 Aspen Trail 2790BHS Travel Trailer
- Shop: Lift Assist
- Search Results: 5200 lbs axle trailer brakes
- Q&A: Recommended Trailer Hitch And Bike Carrier For Forest River R Pod
- Q&A: Testing a Vehicle Side 7-Way Trailer Connector for Proper Function
- Video: All You Need to Know About the Deka Heat Shrink Butt Connector
- Q&A: What Gauge Wire Should be Used to Wire Trailer Brakes
- Q&A: Troubleshooting Large Voltage Drop On Trailer Brake Wiring When Bypassing With Battery Power
- Q&A: 3,500LB Trailer Axle Self-Adjusting Electric Brakes and Hub For 13" Diameter Wheels
- Video: All About the Dexter Electric Trailer Brakes
- Video: Easy Grease Trailer Hub and Drum Assembly for 5.2K & 6K Axles: The Breakdown
- Video: Detailed Breakdown of the Dexter Trailer Hub and Drum Assembly for 3,500-lb Axles
- Video: Detailed Breakdown of the etrailer Electric Trailer Brakes
- Video: Replacement Front Cover for Lippert Edge Awnings Feature Review
- Search Results: leveling jacks
- Search Results: tonneau cover
- Search Results: trailer jack
- Search Results: boat fenders
Wes
3/13/2025
I have the same issue, all new wires clean surface for grounds. Have 12 volts on the brake wire once I engage the trailer brake system it drops to 7.5