Replacing trailer wiring harness

[Viajante]

Has anyone replaced the harness? Any problem with matching the colors? Some reviews say not all harnesses use the same color codes. Thanks.

For example https://www.etrailer.com/Trailer-Wir...s/HM20087.html

[Centex]

If you've any doubt, just do a quick and simple correlation between connector pins and wire-ends with a meter. One of the old before removal and one of the new before installation - make a simple table to track any differences and ensure the new wires go to the correct points in the junction box.

Attached FYI is an example of one I did when swapping the trailer umbilical socket on a vehicle (basically the same situation)

[edlynnrich]

That’s interesting. I had thought that the color codes had been standardized. That would have been a major screwup!

[Tonny LR]

I had replaced the ETI 7 way RV trailer plug wiring with Pollack plug. I got it from E-trailer. Pollak Black Plastic, 7-Pole, RV-Style Trailer Connector - Trailer End
Item # PK12706. The ETI trailer plug did not contact well the my Yukon SUV connector, and constantly gave false alert indicating trailer not connected.

Tonny LR

[Brian B-P]

There are two common colour codings. One is an industry common practice from when the RV style 7-way connectors (as used for an Escape) were introduced (probably by Bargman); the other is an SAE standard for trailer wiring that is used with 4, 5, 6, and 7 pin connections. Keep in mind that commercial trucks use a 7-pin connector (sometimes called "7 round" or "round pin") which is physically incompatible with the 7-way RV connector (sometimes called "7 blade" or "flat blade"), and has different functions (separate turn signals, clearance lamps separate from tail lamps, no brake signal or charge line). It doesn't make much sense to me to apply the SAE standard to the RV connection, but some people do it; In the guide Hopkins shows the SAE standard for the commercial connector, the RV standard for the RV (blade) connector... and the SAE colours on the RV (blade connector).

Colour coding within a vehicle is specific to the vehicle, and shouldn't in general be expected to follow any standard for trailer wiring.

The colour coding is just an annoyance if you are aware of it. I think a bigger concern is wire gauge: the higher-current brake and charge conductors should be larger gauge than the lighting circuit conductors, and the negative/ground conductor carries the total current of all the circuits so it should have an even larger gauge. The commercial truck cable needs to handle high lighting loads (lots of lights, traditionally incandescent) and no charging or brake loads.

The linked Hopkins cable has the connector already on it, so it is specifically for the RV connection and should have appropriate conductor gauges... but they're not listed. Even the product listing on their website doesn't include wire gauges, although this is provided for some other cables from other sources.

[Vermilye]

Originally Posted by Viajante

Has anyone replaced the harness? Any problem with matching the colors? Some reviews say not all harnesses use the same color codes. Thanks.

For example https://www.etrailer.com/Trailer-Wir...s/HM20087.html

I replaced the original connector/harness provided with my 2017 21 with the one in the link above. I had problems with the original connector in both my Tacoma & F150 - while it never fell out, the brake & tail light pins were intermittent.

While it has been a while, I do remember that the wire colors & the color labels in the connection box attached to the trailer rails were different. I used the pin numbers and an ohm meter when wiring to be sure I ended up with the correct connections.

By the way, the linked connector is excellent. While expensive, it fits snuggly in the F 150 connector.

[Viajante]

I went with the Hopkins harness. The colors don’t match. The original harness follows the RV standard and the Hopkins is SAE automotive. Hopkins provides a conversion diagram.

You can use the original harness to identify and tag the proper connections in the junction box, then make the new color connection based on the conversion diagram.

I took Centax advice to test the original with a meter to confirm the function of each wire.

The wire gauges on the new harness matched the original. Ground and charging wires are 10 ga, electric brakes uses 12 ga, and the lights are 14. There is an unused wire for backup lights that dead ends in the junction box.

Even though some of the wire colors don’t match the connector does match. It isn’t a difficult job.

Thanks for the good and pertinent comments.