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mgambalie · 03-25-2019, 08:37 PM

2000 Tradewinds, Freightliner Chasis

I feel like an idiot -- silly me, I expected my factory wired plug to "just work", what could be simpler, plug in and go, right?!?
I purchased a tow dolly from Craig's List, supposed to pick it up later this week 1/2 way to Florida from home. Seller emailed me the connection specs, I purchased a 6 to 4 adapter and a drop hitch from Amazon that arrived this afternoon. For grins and chuckles, thought I should test the pins on the flat-4...
Long story short, going back to the factory 6, I have no 12v power on any pin. 5 are wired, 4 of the 5 short to ground (beep my meter).
Are there a separate fuses for the tow connector or do they share the same wire/fuse as the lights? If there is a separate, how might they be labeled? I have the National distribution center diagram - nothing jumps out at me. Also the Freightliner fuse box below the drivers seat - it shows tail lights, signals, etc but nothing obvious for towing.
Any direction is most appreciated.

mg

aether_one · 03-25-2019, 08:44 PM

Don't use a continuity tester (ohmmeter), use a voltmeter to test when the appropriate light is on.

mgambalie · 03-25-2019, 08:53 PM

I used the volt meter first, got zip, then tried continuity from each pin to ground.
mg

mgambalie · 03-25-2019, 09:01 PM

Inspecting the fuse/wiring box up front again, there are 2 more banks of fuses that are not identified. Does Freightliner post a diagram or chart? I searched google and their website, perhaps I am not using the proper terms.

mgambalie · 03-26-2019, 10:42 AM

I was able to locate the Freightliner fuse diagrams. For future reference, https://www.rvtechlibrary.com/ is a huge resource of manuals for multiple systems and chassis.

The first part of my issue is corrosion, inside the wiring plugs. There is a 7-pin weatherproof connector from the chassis wiring harness that feeds 2 6-pin Molex connectors, one for the tow plug and the other for rear lights, so at least the lighting circuits are common - not fused separately. Since the same connector was feeding the (working) rear lights, I opened the Molex to the tow connector, sprayed with WD-40, opened and closed it a couple of times to clean the pins, and I now have power at the tow plug.
I don't have ground.
Not even at the 7-pin. The wiring behind that goes through the frame into the engine compartment -- I figure its going to take some time to hunt it down -- so I installed a temporary ground wire directly to the tow plug; I hope that will suffice for the next couple of weeks.

WorldCat25 · 03-26-2019, 02:26 PM

Does anyone know if the 7 wire RV plug is wired the same as the 7 wire plugs on other than RV's (SUVs, pickup, big trucks)?

One would certainly think so but I have my doubts.

stevemoores · 03-26-2019, 03:57 PM

Quote:

Originally Posted by WorldCat25

Does anyone know if the 7 wire RV plug is wired the same as the 7 wire plugs on other than RV's (SUVs, pickup, big trucks)?

One would certainly think so but I have my doubts.

It should be.

I had a similar issue with mine when I bought ir. It had never been used for towing, the socket on the back of the motorhome was just full of corrosion, it had traveled up the wires a couple of feet.

I had to cut the wires back to clean copper and re-wire (solder and heat-shrink the joints). I just followed pictures online for the colour codes, checking with a volt-meter as I went. Amazingly it all worked.

Steve

THenne1713 · 03-30-2019, 12:50 AM

Better is a 6-pin/ 7-pin TESTER that just plugs in, check Amazon (under $10)

THenne1713 · 03-30-2019, 12:52 AM

I did a google search, believe etrailer.com shows a variety of plug options/ variances

ScoobyDoo · 03-30-2019, 05:16 AM

Quote:

Originally Posted by THenne1713

Better is a 6-pin/ 7-pin TESTER that just plugs in, check Amazon (under $10)

Well maybe. But say you have a bad ground on the TV. You plug your fancy little tester, the ground is good enough, to carry all the currant needed to light the little pity LEDs. You plug in your trailer, and things don't work. Now you spend the next 3 days pulling your hair, and cobbling up the wiring of the trailer before you call somebody that knows what they are doing. Took me 1 minute to find the original problem, 10 minutes to fix. Hours on the trailer...