How use a voltmeter to test trailer wiring

[mattwahm]

I need to troubleshoot why all of my trailer lights are not working. I'm guessing there is a bad ground somewhere. However, I'd like to test the connector on my tow vehicle and trailer, as well as the power going to the lights. I have a yellow voltmeter from Wal-mart, but I've never used it. Can I get a quick "how-to" on using this meter? There are a lot of different settings that I'm not very familiar with.

 

[tashasdaddy]

Re: How use a voltmeter to test trailer wiring

this is the easiest way to test the vehicle. http://www.iboats.com/Seasense_Ez_T...3903806--list_time.1178661152--view_id.237539

end the hassle of bad lights, and run a wire down each side of the trailer and ground it to the mounting bolt of the lights, then connect to white wire on harness.

http://forums.iboats.com/showthread.php?t=194735

 

[bruceb58]

Re: How use a voltmeter to test trailer wiring

http://www.ehow.com/how_16767_voltmeter.html

And you don't need to run a seperate ground to every light. Your trailer is a very good conductor...it's the connections to this conductor that matter.

Tasha, you always make this comment and I always refute it. Think of the trailer as a ground plane of a circuit board. All the parts on the circuit board get their grounds from this ground plane. Grounding every component with its own seperate ground wire is not only superfluous it is adding more connections with a greater chance of failure.

No trailer manuafcturer uses an extra ground wire because it is not needed.

 

[tashasdaddy]

Re: How use a voltmeter to test trailer wiring

Bruce, i say it and will continue to. and you can keep refuting it. but i started doing this, with construction trailers that take a real beating. then went to my boat trailers. i have never in 20 years had a problem other than burnt out bulbs. i remember the time when the ground was thru the hitch and ball, no white wire on the connector.

 

[bruceb58]

Re: How use a voltmeter to test trailer wiring

I have owned boat trailers for 25 years and have never needed to do anything but make sure the grounds at the lights were properly cleaned.

Putting the extra wire is a band-aid solution covering the real fixable problem.

I also have never relied on a ground through the hitch.

 

[drewpster]

Re: How use a voltmeter to test trailer wiring

I also have never relied on a ground through the hitch.

Bruce, You know by now I respect your opinion but I have to go with TD on this one. I think where you two are crossing swords lies in the quote above. I always run a separate ground on my trailers. It seems my lights were forever going dim or ceasing to function altogether until I started running a ground directly to them.

Incidentally all the trailers on every semi on the road has a dedicated ground from the truck to all the lights. (and ground problems are still a plague)

 

[Silvertip]

Re: How use a voltmeter to test trailer wiring

And I side with Bruce. The metal in the trailer frame is an excellent ground but you do need ground jumpers to span pivot points on tilt style trailers. If the lamp assemblies are grounded properly there will be no ground problem. As for testing trailer lights, the LED devices are useful only to prove the tow vehicle lights are ok. They are no help for diagnostic purposes if they don't work. As for the trailer, I use flat four connector with all three power leads connected together. Then connect a battery charger (+) to those three leads. Connect the battery charger (-) to the ground lead. You can now chase 12V down each line until you lose it at which point you found the problem.

 

[SuperNova]

Re: How use a voltmeter to test trailer wiring

Yeah, I'm with Bruce as well. I have never run independent grounds to all the lights. Even car manufacturers use common grounds on the body and frame; they don't run ground wires back to the battery for everything.
--
Stan

 

[Rob454]

Re: How use a voltmeter to test trailer wiring

i usually run the ground wire ( white) that comes from the plugs. the trailer side gets screwed down to the trailer then the truck side is part of the harness. The trailer ball is not the best place to get a ground IMO. you want a constant ground and if youre on rough roads and stuff the trailer ball rattles in the trailer socket, the trailer receiver is rusted out etc)
now I also run the light grounds to the trailer and I use the trailer as the conductor. you can run a ground wire along with the turn stop light wires which would be the better way to do it btu I usually dont.
As for the meter depends on what functions you have
you shoudl have a VDC 9 volts Direct current0 VAC ( volts alternating current)
Ohm ( looks liek a upside down horse shoe) Amp ( amperage) Now you amy also have a selector for a range of the above mentioned but the cheaper ones usually dont.

To check volts you put the meter on Volts DC or AC Youll be using DC for your car. You want to check for voltage at the plug. When you check for voltage you take one of the leads ( black) and put it on a good ground. then take the red and put it in the terminal you want to check. You shoudl get voltage. it should read 12.7 vdc. NOW if you reverse the leads then it will read -12.7vdc. what the - means is you have the polarity reversed. this way if youre checking some wires you dont know youll know youll know whats ground and pos

 

[zeldazada]

If you’re anything like me, the first time you hit the road with a trailer in tow, you had a moment of panic when one of your lights suddenly went out. What do you do? How do you fix it? Don’t worry – testing trailer lights with a multimeter is actually a lot simpler than you might think! In this guide here

 

[The Force power]

If you’re anything like me, the first time you hit the road with a trailer in tow, you had a moment of panic when one of your lights suddenly went out. What do you do? How do you fix it? Don’t worry – testing trailer lights with a multimeter is actually a lot simpler than you might think! In this guide here

Thanks for coming out, this tread is 13 years old perhaps you should read the guide on how to use this forum