Trailer Wiring

[JB4310]

I will start a new thread here so not to hijack "brake controller" thread.
First of all I don't have any problems with either of my trailers, a 5 ton dumper and a 20 foot equipment trailer.

But with all this talk about trailer brakes and wiring etc I started looking how mine worked, I know, if it ain't broke don't fix it.
Anyway it started with the break away battery system on the equipment trailer, as far as I can tell mine does not get charged, next time it's hooked up I'll check the voltage to see if it's higher than 12 volt when the truck is connected and running, indicating it is indeed getting charged.
The reason I don't think it is, is because there is only one black wire coming off the battery and I'm pretty sure it goes straight to the break away switch, so how could it get charged?

Next is while trying to figure that out I was checking the 7 pin connectors, trying to determine where power could come from.

So this is the weird part, kind of a question and kind of just a statement. While checking my trucks 7 pin outlet I find I'm getting voltage from almost all the terminals except the running light blade at the 11 o'clock position and the ground.

Specifically as follows:
with key off, actually no key in ignition.

terminal at the 1 o'clock position, bat+ = 12.9 volts
term @ 3 o'clock, RT turn/stop light 8.9
term @ 5 o'clock, elect brakes 11.3
term @ 7 o'clock, ground 0
term @ 9 o'clock, left turn/stop light 1.3
term @ 11 o'clock, running lights .1
center terminal 3.9



with truck idling. but no lights on or brakes pressed.

term 1 o'c 14 volts
term 3 o'c 2.5
term 5 o'c 12.1
term 7 o'c 0
term 9 o'c .6
term 11 o'c .3
center term 3.9


Am I crazy, stupid or just unqualified to operate a multi meter?
How is this possible, like I said everything works the way it's supposed to, used both trailers this week lights and brakes work flawlessly. how could there be voltage at those terminals with nothing on especially the brake circuit? the only one that makes sense is the hot term reading of 12.9 with truck off and 14 when running.
I have the Drawtite Activator 2 controller.

ANY IDEAS ???

JB.

 

[Diamondpilot]

You should have zero volts with the key off and with the truck running you should only have voltage on the term at 1 o clock. You have to have a bad connector somewhere on your truck. I would look at all the connections under the truck where they are in the weather. I would also take apart the 7 pin female plug on the back of the truck and look for water or a short.

You say everything is ok, but its not. Say you had a boat and left the trailer hooked up for 2 or 3 days why you took a trip. When you got back to the boat ramp to start the truck you would have a dead battery due to the drain on the system.

Chris

 

[MarkLeininger]

I agree with everything Chris said except the voltage at 1 oclock might well be the battery voltage with the vehicle off. I think it is common to run a wire directly from battery positive to the pin at 1 oclock.

You definitely have a problem, not the least of which is that your trailer brakes are full on all the time. I'd pull your drums to see if there's anything left of the brake shoes. I would start by pulling the 7 pin apart, could be water and corrosion, or a single loose strand of copper wire is acting like fur, touching some of the connectors and carrying a slight current. I've also had insects make little nests in there and when they get wet they act like a sponge and short everything out.

 

[Diamondpilot]

I agree with everything Chris said except the voltage at 1 oclock might well be the battery voltage with the vehicle off. I think it is common to run a wire directly from battery positive to the pin at 1 oclock.

Mark and others, it is fine to do it that way but the problem is as the battery on the trailer drains it will pull down your tow vehicles battery if not running. It will not be a problem except if you were using a travel trailer or something similar it is possible to get in a situation where the tow vehicle will not start, like camping overnight with it still hitched up. Even a dump trailer hitched up the night before a big job may drain the trucks battery enough to not start in the morning.

Most factory installs and good aftermarket installs run it though a relay that allows it to only be hot with the tow vehicles key on or running. Prevents the above situation from happening. Trust me, it happens. My neighbor had a camper that stayed at a a remote property for a year. When they got there to take it home they hitched it up then spent the day having one last visit and cleaning up the site. When they went to start the truck and guess what. I got called out to drive 45 miles each way to jump start the truck. It was a 96 Dodge wired hot all the time and my guess as to what happened is the battery on the trailer was low and pulled a charge off the trucks battery. Got them both so low it would not start.

Chris

 

[JB4310]

You say everything is ok, but its not. Say you had a boat and left the trailer hooked up for 2 or 3 days why you took a trip. When you got back to the boat ramp to start the truck you would have a dead battery due to the drain on the system.

Chris

It' crazy! when I say everything works flawlessly I mean it, brakes work perfectly, I dial them in as needed for different loads, lights all work normally. Truck is an 07 Dodge 3500, wiring was done by a top notch body up-fitter shop when I got my utility body installed.

I don't want to start taking stuff apart to fix some phantom problem, I know it doesn't make any sense, I even tried 2 meters my old analog and my new digital, it is bothering me, what if I was trying to diagnose a problem and I'd be getting all these whacking voltage readings, what could I be doing wrong? to do the testing I am using the ground blade in the socket for ground connection.

Unless I shorted something out doing all this poking around, haven't had the trailer on since I started doing the testing. or when the trailer plug is plugged in it straightens it all out???

Any other ideas, even unconventional ones.

JB.

 

[Diamondpilot]

I really think you have moisture in one of the connectors the truck bed people had apart. They probably used the factory end then connected something they made up to it to get the lights on the bed to work. I am guessing the problem is there. Basically a lack of dielectric grease or a shorted pin.

Chris

 

[jones6780]

If I remember correctly, my controller sends a low apmerage current through the brake terminal and it is used to detect when the trailer is connected.
Russell

 

[tommu56]

On some new solid state equipment they might have some voltage on it even with it off. maybe they are using solid state in the vehicles?

A while a go we had a new apprentice at work had a similar problem with a solid state relay he put a meter on output and he was jumping around that out put was on and the light was off on the relay that the relay was bad I walked over with my wiggy and there wasn't any voltage on it.

He put his meter on with my wiggy and it read 0 he was confused I explained that there wasen't enough load on his meter to load the out put right.
I got a lamp and put it on and it didn't glow till we turned on relay

tom

 

[Diamondpilot]

Here is a guy who has had the same issues as you on his Construction equipment.

http://www.tractorbynet.com/forums/trailers-transportation/140691-big-tex-follow-up-2.html

Chris

 

[Soundguy]

Any other ideas, even unconventional ones.

JB.

Hate to say it.. but maybee.. as you mentioned in the first message.. you are unqualified to run that meter.

what's a testlamp show you on those pins..

soundguy