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Want to add work lights


alan0043
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Hi Everyone,

I am in the planning stage of wanting to add two work lights to the back of the tuck. I have a few questions. I already have the lights. They are Ironton brand 18w LED work lights. The place on the truck that I would like to add the lights are in the upper corners behind the sleeper. I want to take advantage of the bracket that is on the truck to hold the lights. I also want to use Ancor marine grade wire. I am not sure what gauge wire to use. I am thinking I can use 16ga. wire. I saw some where that 16ga wire is good for 20w. Is that right ? If not, what gauge wire do I need ? I do have a spare fuse box wired in the truck in the drivers side storage compartment that I will use to get the power from. What other parts do I need ? Always looking for ideas.

Thank you for any help,
Al

 

 

 

 

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This is a pretty good Automotive Wire Size Calculator.  The wire size needed is dependent on amperage and length of wire.  Your lights will use (18 x 2) 36 watts.  Current = Power/Voltage or 3 amps.  Plug 3 amps and your wire length into this calculator to see what minimum size wire to use.  Using bigger wire is always a plus.

https://www.wirebarn.com/Wire-Calculator-_ep_41.html

Read the notes at the bottom of the calculator, specifically the one on this being a "One Way" calculator.

Other parts?  Good crimp on connectors unless you want to solder them. 

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Alan, I would think about running 14ga wire just to make sure you don't have any problems with voltage drop, but 16ga should work fine. I would also get some butt connectors that have the heat shrink tubing on them like these: image.thumb.jpeg.933644e5364f66b4bcf91bd4e8d7ec2a.jpeg

Also, make sure the crimpers you use don't puncture the plastic or you may as well not even use these type.

Tom

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As a matter of habit, I always wire stuff like that with 12 ga. Overkill for sure, but I have less wire around, and I can upgrade the load without re-wiring if I want too, latter.

If you are not tying the lights into the cab light switch for the load lights, then you might consider an outdoor switch accessible from the ground. We generally put two sets of lights on - one is the replacement for the lights on the fairings. The second are additional load/work lights like you are doing. Those we tie to direct power with an outdoor switch. That way if you are working on the truck without it running you can simply turn them on/off at will.

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The wire size calculator above is for a one sided circuit using a fixture that is grounded to the chassis. 

If a wire (positive) is run from the panel to the fixture and a 2nd wire (negative) runs back to the panel .....or the length of wire (negative) that is used to ground the fixture to the chassis needs to be added to obtain the correct wire size.

If the input voltage of the LED fixtures is say 9-18 volts a 10% voltage drop is O.K.  

Bit of trivia.......marine (tinned) 18/2 to 12/2 will fit through a PG9 (3/8"NPT) strain relief while 10/2 needs a PG11 (1/2"NPT) strain relief. 

Edited by J-T
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20 hours ago, NeverEasy said:

This is a pretty good Automotive Wire Size Calculator.  The wire size needed is dependent on amperage and length of wire.  Your lights will use (18 x 2) 36 watts.  Current = Power/Voltage or 3 amps.  Plug 3 amps and your wire length into this calculator to see what minimum size wire to use.  Using bigger wire is always a plus.

https://www.wirebarn.com/Wire-Calculator-_ep_41.html

Read the notes at the bottom of the calculator, specifically the one on this being a "One Way" calculator.

Other parts?  Good crimp on connectors unless you want to solder them. 

Thank you for the calculator.
Al

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On ‎9‎/‎17‎/‎2017 at 1:09 PM, Jack Mayer said:

As a matter of habit, I always wire stuff like that with 12 ga. Overkill for sure, but I have less wire around, and I can upgrade the load without re-wiring if I want too, latter.

If you are not tying the lights into the cab light switch for the load lights, then you might consider an outdoor switch accessible from the ground. We generally put two sets of lights on - one is the replacement for the lights on the fairings. The second are additional load/work lights like you are doing. Those we tie to direct power with an outdoor switch. That way if you are working on the truck without it running you can simply turn them on/off at will.

Hi Jack,

If I read this right, are you talking about a 3 way light switch ? It would be nice to turn the lights on from the ground and not have to get up in the cab. I am hoping to get to the nationals. Maybe I can get together with you to see how you do this job. I do have the mounting holes drilled in the truck now. I also have some 12ga marine wire. Maybe this could be a project at the nationals.

Al

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I don't put in a three way. For work lights you will almost always be on the ground next to the lights....in fact I can think of no circumstance that is otherwise. If you are backing up you are not using the work lights but the backup lights on the fairings.  So with the work lights I just put an external switch in a convenient spot near the fairings. On this truck, it is attached to the cab near where the tractor protection valve was. The TPV was relocated during singling.

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I just use a relay on a low amperage circuit like you are talking about. Use post 87A to feed your switch on the back of the truck on key off conditions and post 87 to feed the light when using the interior switch as the trigger for the relay. Just make sure you are fused correctly and use a diode if required to prevent problems.

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3 hours ago, Jack Mayer said:

For work lights you will almost always be on the ground next to the lights....in fact I can think of no circumstance that is otherwise.

I would agree with Jack but how many times have you crawled into the cab and look back and see you left the lights on?  This is easier than a relay..

Three-way light switch.png

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21 hours ago, NeverEasy said:

I would agree with Jack but how many times have you crawled into the cab and look back and see you left the lights on?  This is easier than a relay..

Three-way light switch.png

Hi NeverEasy,

Thank you for posting the wiring diagram. This is going to be a big help. This is a rookie question. The SPDT ( single pole double throw) switches, can they be bought at the big auto part stores ? Is there an amperage that I need for the SPDT switches ? Will any rocker switch work ? Maybe I can get the parts together before the nationals.

Please keep the help coming,
Al

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Alan, you should be able to get switches at just about any auto parts store. You are only looking at about 3A or so load, so if you find any rated at 5A or above you will have plenty of reserve. If you want to see what is available take a look at this site: http://www.wiringproducts.com/rocker-switches

 

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