Skip the auto shop - Our mechanics make house calls

Q: installed wire harness kit causing brake lights to stay on trailer and causing brake lights on car not to work

asked by on

I installed a wire harness kit into my car and connected it to my camper trailer. The running lights and blinkers work, but the brake lights on the trailer are always on. I disconnected everything then reconnected it and tested to see if it would work properly. It didn't work right for long - only 10 minutes. I checked the pin voltage at each pin of the 4 pin connector and got 12 volts when the brake pedal is not applied. Now my brake lights on my car won't work including the top brake light. Did I somehow cause something to short out?

A: Hello there, it sounds like something may h...

Hello there, it sounds like something may have shorted out. The brake switch system can only support so many amps of power, and with the addition of the trailer lights, it may have exceeded the capacity and caused the fuse to blow. Most likely the trailer brake is wired wrong or has exceeded the capacity of the system it was attached to. A qualified technician such as one from YourMechanic will be able to diagnose your brake lights and perform any repairs required.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Car horn problem

Hey there. In addition to being a requirement for motor vehicle inspection in every state, the horn is obviously a huge safety component. By all means, you should try to get this working correctly. It is somewhat unusual for a...

Q: Charging system failure.

This may be a sign of a weak battery, a failing voltage regulator or failing alternator. As you may know, the alternator is responsible for charging the battery while the engine runs by generating amperage and recharging the battery while...

Q: Door lock not working

If none of the locks work manually, you're using the wrong key, or somehow the key has been damaged. A key from one Honda vehicle will easily slip into the lock cylinder of another, but then won't unlock the door....

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...