Powered by Blogger.
We are saddened to announce the passing of Gary Bunzer on April 17, 2020. We hope the RV Doctor website will continue to provide helpful information for you. Thank you for your interest and support for the RV Doctor - Debbie, Heather and Gretchen

Tuesday, April 13, 2010

RV Tow Wiring

I own a 2005 Newmar Dutch Star. On a recent trip I noted that the left turn signal and brake light on my towed auto was not working when connected to the motorhome. The turn signal on both the motorhome and the car work fine independently. A check of the electrical connection between the motorhome and the auto indicates no power to the left turn/brake light pin on the motorhome connector. I am searching for the cause but there are huge bundles of wires and I am trying to avoid unwrapping them all. My questions: Do motorhomes have in-line fuses for the towing electrical connector? Are the towing electrical connections paralleled with the motorhome stop and turn signals? Are crimp connectors usually used? I did find a connector or fuse holder that looked like it had reset switches but I did not reconnect the connector nor do I know how to reset or replace the fuses if there are any.
Henry, (Pensacola, FL)

Henry, I suspect the problem is likely to found at the multi-pin connector itself. I’m assuming you have a typical six or 7-pin connector on the motorhome. All the wires from the connector are spliced directly into the coach circuits. Typically there are no fuses or breakers involved in the harness itself, but certainly each of those circuits in the motorhome are protected somewhere.

Perhaps the left turn pin on the connector is dirty, corroded or otherwise not making a good contact. Looking at the connector on the motorhome equipped with a standard 7-pin connector, the left turn pin is the one at the 9 o’clock position. Probe this pin for power while the left turn signal is activated. I would probably measure the actual voltage at that connection in case there is some voltage drop to consider. If the connection or contact is dirty or corroded it may be necessary to clean or burnish the contact before obtaining a reliable measurement. You can use a small screwdriver or dental pick to carefully scrape any debris off the contacts. Also make sure all the pins make solid contact with the towed vehicle plug. Make sure that all the internal plug connectors are not bent thereby minimizing the actual metal-to-metal contact. If they are bent too far, carefully move them back into position with a small screwdriver. Do the same with the towed vehicle end of the 7-pin connector.

Remember, when looking at the car end of the harness, the pin locations will be reversed so the left turn pin will be at the 3 o’clock position. In case the problem does lie elsewhere, you will need to trace the wire going from the coach wiring harness to the 7-pin connector. Tow harness are usually tapped into existing circuits (paralleled) using some type of solderless connection. These connections can sometimes become faulty, especially when they are exposed to the elements under the motorhome. In some cases it’s actually easier running a new wire than trying to locate a fault. Especially if it involves unwrapping some thick harnesses! I’d spend a few minutes diagnosing where the problem might be, and then simply run a new wire by tapping into the left turn circuit at the rear of the lamp assembly.


In all instances, every effort is made to ensure the correctness of all content on the RV Doctor Website. It is imperative that if you choose to follow any instructions or procedures outlined on any page of this website, you must first satisfy yourself thoroughly that neither personal nor product safety will be compromised or jeopardized.

All rights reserved.

If you are in doubt or do not feel comfortable about a procedure, do not continue. Simply call your local RV service facility and make an appointment with them. The advice, recommendations and procedures offered by the RV Doctor are solely those of Gary. They do not necessarily reflect the opinions, procedures and recommendations of our sponsors or advertisers.