Troubleshooting Trailer Wiring When Connecting a 4 Flat Vehicle Side to 4 Flat-5 Wire Trailer
Question:
I have a 2001 Isuzu Rodeo and was recently trying to connect the connector wires to my trailer. My Rodeo is setup to use a 4 flat female end that runs to 4 wires Ground, Tail, L Turn, R Turn to a converter that connects the 4 wires of the end to 5 wires which run into the vehicles electrical system. On the trailer, I have a 4 flat male end that connects to 5 wires of the trailer system. Both connectors fit fine, but the turn signals and brake lights dont work the only thing that works is when I turn my headlights on my car, all the lights of the trailer light up. Interestingly when I reverse all the connections connecting the three main pins on each, but each ground isnt connected to anything the brake lights work, but when I turn the right signal indicator on my car, both of the turn signals on the trailer start blinking. Is the problem due to the fact that I am going from 5 wires of my trailer to 4 wires of my vehicle? I havent found a part that allows me to have a 4 flat female end that runs to 5 wires directly. I have a trailer light tester and used it on my car wiring and the signal lights and brake lights appear to work just fine. Thanks for any help.
asked by: Michael G
Expert Reply:
The issue you are finding with your 2001 Isuzu Rodeo and your trailer doesn't have to do with the 4 wire vehicle side and the 5 wire trailer 4-way. Many trailers use what is called a wishbone harness that will run two wires to the same pin for the running lights. This style of harness simply make it so no jump wire is run from one side of the trailer to the other to pick up that running light signal because it is independently run to each side from the connector.
The issues you are finding with your trailer most likely have to do with a poor ground connection. It sounds like your vehicle side works fine with the tester so I'd focus on the trailer. When a trailer has a poor ground connection it is common for some of the features to fail to work properly. When you turn your headlights on the trailer suddenly gets the power it needs because the boost in power from that feature is overcoming the poor ground.
The solution is to clean your ground connection making sure it is free of rust, debris, or any other corrosion. It needs a bare metal to metal connection. Once you have done this with the common ground to the frame of your trailer, you may also need to do this at your tail lights. Often there is a separate ground wire for each or they use the mounting hardware as their ground connection. Even paint can stand in the way of the solid ground connection you need for proper function.
I've attached a couple articles to further assist.
Product Page this Question was Asked From
4-Way Flat Trailer Connector w/ 60" Harness and Wire Taps
- Trailer Wiring
- Trailer Connectors
- Vehicle End Connector
- 0 - 5 Feet Long
- Plug and Lead
- 4 Flat
- Tekonsha
more information >
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Jason S.
7/23/2018
The issue you are finding with your 2001 Isuzu Rodeo and your trailer doesn't have to do with the 4 wire vehicle side and the 5 wire trailer 4-way. Many trailers use what is called a wishbone harness that will run two wires to the same pin for the running lights. This style of harness simply make it so no jump wire is run from one side of the trailer to the other to pick up that running light signal because it is independently run to each side from the connector. The issues you are finding with your trailer most likely have to do with a poor ground connection. It sounds like your vehicle side works fine with the tester so I'd focus on the trailer. When a trailer has a poor ground connection it is common for some of the features to fail to work properly. When you turn your headlights on the trailer suddenly gets the power it needs because the boost in power from that feature is overcoming the poor ground. The solution is to clean your ground connection making sure it is free of rust, debris, or any other corrosion. It needs a bare metal to metal connection. Once you have done this with the common ground to the frame of your trailer, you may also need to do this at your tail lights. Often there is a separate ground wire for each or they use the mounting hardware as their ground connection. Even paint can stand in the way of the solid ground connection you need for proper function. I've attached a couple articles to further assist.