paulkeogh
26.05.2021 18:33:34
Re: How use a voltmeter to test trailer wiring here
See full version: How use a voltmeter to test trailer wiring
Re: How use a voltmeter to test trailer wiring here
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) [links]
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.
Re: How use a voltmeter to test trailer wiring
Re: How use a voltmeter to test trailer wiring
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It's important that your trailer lights are in proper working condition so that other drivers will see you signal and brake. If your trailer lights seem to be malfunctioning, you can test them in several ways to possibly diagnose and fix the problem yourself. First, you'll want to do a simple test with someone else to verify that they are working. If they aren't, you can use tools like a tow-vehicle light tester and multimeter to see if the wires and contacts within your trailer's circuitry are broken.
There are many great multimeters on the market, but I have my own personal favorites which are perfect for automotive uses:
You may have other types of plugs which have 3, 4, 5 or 6 different connections but for this one, I’ll focus on the most common 7-pin plug. more
We recommend using Innova 3340 for this task
The plug is almost always set up in the exact same fashion, although if you are not sure you can refer back to the original guide you got when you purchased it. A typical 7-pin plug will be setup in the below fashion: more
The 7-pin trailer plug is complicated because it hosts 7 different connections all in one (watch the video right below this paragraph).
You’ll need the following items in order to test it effectively:
Go to the trailer connector on the back of the tow vehicle with your multimeter. Have your helper hold down the brake pedal while you probe the terminal that is connected to the blue wire in the connector; in a properly wired connector this wire is the brake control wire and will have voltage present when the tow vehicle brake is applied. The amount of voltage present will vary as your helper moves the adjustment control on the brake controller. No voltage, or a voltage that does not vary, indicates a faulty controller or a problem with the blue wire itself.
Press down on the brake pedal while watching the brake controller. The display on the controller should light up and hold a relatively steady reading, which should not vary by more than 1/10 of a volt up and down. It may be necessary to turn the ignition key to the "On" position for this step. more
Electric trailer brakes must be controlled by a brake controller mounted in the towing vehicle within easy reach of the driver. This allows quick and easy adjustments to the controller to provide for different levels of brake application for varying trailer loads. This adjustment regulates the voltage available for the electric brakes; higher voltages apply the brakes more firmly than lower levels do. A sudden loss of the ability to modulate the level of brake application may indicate controller failure. Testing for this problem is well within the ability of most weekend mechanics, and requires a minimum amount of equipment.
Check the fuse to the controller if the display does not light up. Replace the fuse if it is burned and repeat the test. Another burned fuse indicates a short circuit that must be found and repaired before further testing of the controller can be done. more
Test for a problem with the blue wire by probing for voltage in the blue wire at the back of the controller. A lack of voltage here, or a voltage that cannot be modulated, indicates a failed controller.