Need wiring help - 2003 Fleetwood/Dolly Wiring

[PDickson]

I have been having trouble with blown brake light fuses after wiring in a new Pollack 7-pole jack on the RV side to match the Roadmaster RM3477 tow dolly.

Previously on the RV the previous owner wired in a flat 5-pole connector. I removed it and used a standard wiring diagram for the new female RV plug. Learned that the tow dolly wiring didn't match. Took both connectors apart to match wiring. Now, blinkers, running lights work correctly.

I could really use some help trying to make sense out of the brake light wiring issue. I spoke to someone at an RV shop - he seems to think I need a jumper of some sort on the RV side "because I have Amber brake lights." I wasn't able to make the correlation.

Here is what I know:

- The brake lights on the RV and dolly work briefly, and then the brake light fuses blows.

- Verified with Roadmaster that wiring is correct on dolly.

- Power being fed back to fuse block is blowing brake light fuses.

- RV plug - black Aux power does not mate to a power wire on the dolly side connector as currently wired.

I have attached a diagram that shows how I am wired on both RV and tow dolly. If anyone can see what I am missing I would love he hear your feedback.

[l1v3fr33ord1]

PDickson-

If you have a voltmeter or test light, then the first thing I would do is put it on the new RV hitch connector pins and see what you get:

1) Put the hazard switch on, look for on/off/on/off... at stop/turn pins (left and right)
2) Turn the hazard lights off. Have someone step on the coach brake pedal. Look for constant 12V on stop/turn pins (left and right)

If it passes those tests, plug in the umbilical at the coach end and repeat tests above, at the dolly end, without the dolly being plugged into the umbilical.

Do those tests, and let us know what you find.

If you used wire colors to wire the hitch connectors or the umbilical cable, you likely have some wires crossed. That's because the wire colors are not standardized. The signals on each pin are standardized. See here for the reference I use the most.

By the way, who made the chassis under your coach, and where are the fuses that are blowing?

[PDickson]

Thanks - good info. I have a Freightliner 3126E chassis - 38ft 330hp CAT. the fuse is blowing in the rear compartment fuse block where the chassis batteries are located.

Here is what I find interesting - yellow and green wire are turn and brake lights (as I understand it). When the brake light fuse blows, the turn signals continue to work.

[Brentw]

Back feed should not blow fuses, you got something else crossed.
Your seven pin wiring share brake and turn lights, if you have a European lights ( separate signals so 4 lights) and are trying to connect to a N/A lights ( 2 lights), you will need a 5 to 4 wire module wired in ahead of the 7 pin.

[l1v3fr33ord1]

Originally Posted by PDickson

Here is what I find interesting - yellow and green wire are turn and brake lights (as I understand it). When the brake light fuse blows, the turn signals continue to work.

Implies the brake signal is not making it onto the stop/turn signal wire. The results of the tests I listed should help sort that out.

[Brentw]

Hope this helps. 5-4 modules are available anywhere you can get trailer wiring parts.

[fairway2002]

Follow your plug wiring back. It should go to a box that has wiring for 7 pin and another for 4/5 (no amber).

[PDickson]

Completed the test of the brake/turn signal, and running lights via the Pollock 7-way connector and received proper readings. It seems that only when connecting the dolly that I blow the brake light fuse. It would seem that the electric brakes, or the 5-4 interface (addressed by BrentW) is a next direction. The turn signals and running lights on the trailer work fine, despite the blown brake light fuses being blown.

Thanks so much, and I am always open to any additional thoughts.

[twinboat]

You need that module mentioned to get your seperate brake light MH to work with a stop/tail light system.

It is possible that back further, where the MH trailer light harness comes from, there will be a junction box that has the yellow and green wire that are stop/tail wired already.

[l1v3fr33ord1]

PDickson-

You say the signals were correct at the coach hitch connector. Did you run the same tests at the dolly end of the umbilical cable? If so, what were the results?

[PDickson]

Thanks, Brent. The problem is that brake and turn signals are already combined in the RV plug wiring. Your diagram shows the brake light and turn signal being individual wires - they are not. The only wire that is on the RV and not on the trailer side is the black power wire.

[PDickson]

Hello Friends

After a tough last couple days scratching my head over the RV to tow dolly wiring today was a turning point. Thanks very much for all of the kind inputs and comments.

It was difficult finding the hitch wiring diagram from Fleetwood - this forced me to go with industry standards of black = power and white = ground. I had good positive voltage on turn signals and running lights as l1v3fr33ord1 suggested I check - thanks. Because I kept blowing brake light fuses I couldn't understand how blinkers kept working when brake lights failed. This is important, as I believed that RV side turn signals also contained brake light signals.

Today's I took apart both connectors and started wiring one wire at a time until I could isolate the shorted circuit. Additionally after a long search I found a hitch wiring diagram for my Fleetwood Excursion 38U hitch plug. Low and behold - black = ground and white = brake lights. This meant that I had a separate brake and turn signal wire. Since the tow dolly had combined brake/blinker wires I had to act on Brent's advice to get a 5 to 4 tail light convertor - thanks Brent.

What I learned:

No industry wiring standard (color) exists - assuming doesn't work with science and math!

Amber turn signals and red brake lights requires a convertor when trailer lights share brake and turn signals.

It was a pain in the butt however I know my RV much more intimately now. Thanks to all of you for coming on with your suggestions and advice. It really did help to connect the dots. In the end I am happy that I didn't take the eAsy route and throw $$$ at the problem.

Paul

[l1v3fr33ord1]

Paul-

I'm happy you solved the problem. It's not unusual for coaches of your vintage to have a separate brake signal wire at the hitch connector. When they do, a converter is needed.

However, your statement

Amber turn signals and red brake lights requires a convertor when trailer lights share brake and turn signals.

is not always correct. A common turn signal switch design provides multiple contacts; one set has separate stop and turn signals, and a second set combines the stop and turn signals. If vehicle designer so chooses, he can use the first set for the vehicle rear lights and the second for the trailer hitch connector. This is how it is in my coach, and many others. A converter is not needed with this design.

An educational experience, indeed!

[PDickson]

Very good info - thanks. And I thought I would be bored in retirement. I am a new full time student - gladly. Thanks again.