How does one test a tow vehicle wiring harness?

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How does one test a tow vehicle wiring harness?

Postby San Diegan » Fri May 06, 2005 10:21 pm

Today I received the Mopar wiring harness kit for my Dodge Magnum. The instructions are in the form of wordless diagrams and are actually quite clear. I even found all of the connections in the electronics module under the hood. I do have to drill two 1 3/4" holes in the unibody under carriage, but I am OK with that. The nice thing about this is that there is no splicing into the taillight or turn signal circuits and activation seems to be based on relays in a module that comes with the kit. And... I'll save about $300 off the parts and installation price from the Dodge boys. At this point, anyway.

Now, how do I test the thing short of a smoke test? I don't want to damage anything in the vehicle's electronics systems. I do have a Craftsman multimeter that can be set for the appropriate voltage/amperage range. I could test the interface pin by pin as Mrs. Diegan turns on the lights, applies the brakes, and so on. That's going to cost me. Is there a better way to go about this?

An additional question arises from the notion that I don't think the kit provides for battery isolation. If one forgets to disconnect it, the tear is still going to drain it's battery as well as that of the tow vehicle. Absent minded professor that I am, should I put a battery isolator solenoid in series with the battery line in the harness?

Finally, would it be wise to fuse the battery line in the harness?

Thanks,

Tom
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Postby madjack » Fri May 06, 2005 11:03 pm

...from back to front;
C) it NEVER hurts to fuse a line from the battery
B) yes if you are running a charge line from vehicle to tear
A) available at most auto parts house is a tester that plugs into the connector on the car

all this presupposes you are running a charge line from the tow vehicle to the tear, if not and you are running just a 4pin flat plug, ignore all but A)
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Postby San Diegan » Fri May 06, 2005 11:34 pm

The Mopar wiring harness kit provides a 7 pin connector. So I guess I am in for the full tilt boogie here. I'll stop by PEP Boys and NAPA before doing this to check for a tester. There is a Campingworld store that is not too far. I'll check there too.

Tom
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Postby madjack » Fri May 06, 2005 11:55 pm

San Diegan wrote:The Mopar wiring harness kit provides a 7 pin connector. So I guess I am in for the full tilt boogie here. I'll stop by PEP Boys and NAPA before doing this to check for a tester. There is a Campingworld store that is not too far. I'll check there too.

Tom



...you big city fellers really upset those of us who live just south of Podunk, we haveta order from the catalogue...can't just go to the Campin'World store and such and have a looksee at what we are a-wantin'(which has resulted in a large pile of stuff I can't use) :cry: :cry: :cry: :lol: ;)
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Postby San Diegan » Sat May 07, 2005 10:18 pm

madjack,

I'm a bon ton Cajun mon stuck in San Diego. Oh sure, I can surf and that's cool, but give me some low country cooking that's the real deal and prepared by somebody other than myself. At least you have that in your part of the country. A roux made with flour browned in pork fat would be the start of a great gumbo right now. Let's throw in the holy trinity, some chicken, andouille, and okra and go for it. Rice. Gotta have rice. Rice, Rice, Rice, Rice. These people out here actually want to reduce their carbs. Idiots. Some people eat to live. Some people live to eat.

What was that about a harness?

Tom
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Postby madjack » Sat May 07, 2005 10:53 pm

...wonder how many people know that the holy trinity actually is...onions, garlic and celery...oh and by the way, we cooked up a crawfish etoufee/sauce picant tonight...sacrebleu. I really feel for ya way out there in the land of fruits and nuts ;)
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Postby San Diegan » Sat May 07, 2005 11:28 pm

We have one Cajun store in San Diego that carries andouille. One. I have to deal with mail order for that if I don't want to go out to boogersville with it's one Cajun store. You get your parts by mail order. I get andouille. That's life man. You can't have everything. Of course, real low country people would make their andouille.

Fruits and nuts? Sure. They have granola here. By the ton. Tastes like sawdust. Granola is the term here for a left over '70s person. I'm one of them, but I moved on.

Meanwhile, I did get those 1 3/4 holes drilled. I've daubed some primer over the raw metal edges and am letting it dry tonight.

Pep Boys and Napa didn't really have anything terribly useful for a tester other than a seven to six adaptor with LEDS on it. At $17.95, it seemed kind of useless. If you hook everything up and it doesn't work, the damage is done.

So, I hooked up the Mopar wiring harness to the electonics module under the hood without routing it or mounting it, plug by plug. It works fine. I'll try the same thing tomorrow after church with the fuse and isolator. Step by step.

Now I am really hungry.

Tom
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Postby madjack » Sun May 08, 2005 12:03 am

...andouille, in San Diego...OMG, whodathunkit. Make my own andouille...naw I just go down to the Rigolette(pronounced ro-gully)Meat Store and get my andouille and boudin...mmm-mmm-mmm, can't beat their boudin
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Postby DestinDave » Sun May 08, 2005 4:31 am

Thanks a lot Tom and Jack! 4:30 in the AM and you got me starvin'. And, yes, a fine roux is the start of just about anything worth eatin'! Whooeee, don't that pretty? Bless you Justain Wilson, wherever you are...
Reality, huh? What a concept!
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Postby San Diegan » Sun May 08, 2005 11:17 pm

Well Dave, if you was Cajun and up at 4:30 AM, we would surmise you never went to sleep from last night. Might still be something in the gumbo pot on the stove.

The harness is installed and working. At least I haven't shorted anything out, everything on the car still works, and all of the pinouts look good with one exception. Pin 2 on the seven wire interface is just labeled as "trailer" and seems to do nothing. The Mopar instructions have one lead it up to the front of the car under various pieces of interior molding, but then just terminate it under the dash. I don't know it's purpose.

Now about that Cajun cooking, guy name Emerill on the food TV claims to be some kind of Cajun cook. Now Pennsylvania has some good points (scrapple, cheese steak sammers, and the like), but he's from Philly, which, for Cajun, is more stupid than a one eyed, three legged dog named "Lucky". You wanna teach Cajun cooking, you better have a name like Uncle Beadreau, it better be the name your mama gave you, and you're going to spend a lot more than one hour on a meal. God bless Aunt Veronique (vay-ron-NEEK) and Uncle Jean Beadreau for raising this Cajun boy right in California.

Hummm. Cajun. Dutch oven. Possibilities. Pass the file', please. (thet's ground, dried, sassafras leaves, for you, oh, well, nevermind).

San
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Postby madjack » Sun May 08, 2005 11:38 pm

...I do believe the pin you are referring to is for your electric brakes
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p.s. more info [url]http://www.easternmarine.com/em_store/tech_info/light_tech.html#wiring]here[/url]
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Postby San Diegan » Sun May 08, 2005 11:51 pm

Brakes. Why didn't I think of that? Now just where to connect that sucker. Uncle Beadreau was right. There's always something more to do.

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Postby madjack » Mon May 09, 2005 12:09 am

...the wire in the car connects to the electric brake controller...an add on and of course the other end connects to the brakes themselves
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Postby roadtrippin » Mon May 09, 2005 1:39 am

Oh man, I miss me some crawfish. :cry:
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Postby San Diegan » Tue May 10, 2005 10:31 pm

OK, here's what we have from the wiring connection diagram (the Mopar pin numbers do not use the analog clock face convention)

1 (white) Ground
2 (light blue) Picture of a trailer
3 (brown) Tail/Running lights
4 (Red) Battery charging
5 (Yellow) Left turn/stop
6 (Light Green) Right turn/stop
7 (Black) Backup lights (ths is the center pin)

So pin 2 just about has to be the trailer brakes. Er, right? The wordless diagram shows how to route it to the front of the passenger compartment and terminate it behind the emergency brake pedal. The diagram does not show where it connects. Presumedly, there is an activation circuit that turns on when the brake pedal is depressed, but I'll be deuced if I know how to connect to it.

I suppose I could e-mail the Dodge boys, but, you know, it's sort of like not asking directions when the next turn might take you where you want to go.

Tom

PS: Would that be Bayou Rigolette on the Red River where you got yer Meat Store? You must be near Alexandria.
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