Battery feed
Controllers need a fused battery-hot feed sized for the unit — not a flimsy tap that collapses under load.
Trailer guide
Brake controller wiring that actually stops the trailer
A brake controller only works if power, ground, and the blue brake output are clean. Intermittent trailer brakes are often a connection problem, not a “bad module.”
Active corridor: Montana · Wyoming · Idaho · Washington — case-by-case beyond.
Field notes
United Mobile RV diagnoses trailer brake issues on the corridor with a meter first — voltage drop and ground quality show up before parts swapping helps.
What has to be right
Ground
A poor ground mimics a failing controller. Chassis ground must be clean metal, not paint or a random screw into carpet.
Blue brake output
The brake signal wire to the trailer connector must be continuous and protected. Chafed blue wires are a classic intermittent.
Manual vs proportional
Setup and gain still matter after wiring is correct. Follow the controller maker’s setup — we do not invent gain charts.
DIY vs book
Reasonable DIY
Connector cleaning, verifying pinouts with a known-good tester, and following the controller install manual if you are comfortable with fused 12V work.
Book UMRT
No brakes, brakes stuck on, melted connectors, or tow-vehicle harness damage — Prefer Text with year/make and photos of the plug and controller.
Owner checklist
- Confirm tow-vehicle plug pinout for your year
- Meter battery feed under load at the controller
- Clean and dielectric-grease connections
- Test brakes in an empty lot before highway speeds
Field reality on the corridor
Measure before you buy parts
Forums love parts lists. A meter, a scale ticket, or a cold pressure check usually beats a guess. Bring photos when you Prefer Text — year, make, and a clear shot of the fault beat a long thread.
DIY boundary
Owners can inspect, document, and do basic setup from manufacturer manuals. Stop when you smell burning, see structural damage, or the fix needs sealed systems, gas work, or high-current DC you are not trained for.
Prefer Text path
Text (616) 606-5277 with symptoms, photos, and location on the MT · WY · ID · WA corridor (case-by-case beyond). Trip fee quoted before we roll.
Not a substitute for on-site
This guide is education. It is not a guarantee, not a certification class, and not a reason to skip manufacturer instructions or local safety rules.
FAQ
Can I wait until the next stop?
If brakes, tires, propane, or CO are involved, no — stabilize and get help. Cosmetic and planning items can wait.
Do you stock every part?
Parts are quoted after diagnosis. We travel the corridor with common tools and meters; special-order parts are called out before work proceeds.
What does a visit cost?
Trip $75 within 30 miles then $1.50/mi each way; labor ~$150/hr with 1-hour minimum / 30-minute increments; diagnostic $175 applied if you proceed.
Where else should I read?
Use the Related links on this page for sibling guides and the matching service line. Start symptoms at /troubleshoot/ when you are chasing a fault tree.
Related: Tires, brakes & TPMS · Trailer service · Troubleshoot hub
Pricing teaser
Trip fee $75 within 30 miles, then $1.50/mi each way. Labor ~$150/hr (1-hour minimum, billed in 30-minute increments). Diagnostic $175 applied toward repair if you proceed.
Credentials (text): Victron Professional Certified Installer · weBoost Authorized Installer · Peplink Certified Associate · Dometic Professional Certified. Starlink = installs only (not a certified partner title).