So Do Auxillary LED Lights Need A Relay.

drizler · Aug 16, 2016

I see more and more things seem to have relays these days . I never used any on my old tractors but I don't want to be frying anything on a 2014 Massey with all it's computer goodies either. I plan on adding just a pair of 18 watt square mounts forward and probably a separate rear facing work flood on a separate switch. So what's the standard installation of lights like this you guys have run?

wploetz · Aug 16, 2016

Your old tractors drew a lot more watts than the LEDs. 18 watts is 1.5 amps at 12 volts so as long as your switch and wiring can handle that, your golden.

PS: You might consider using inline fuse holders when you wire the auxiliary lights.

kthompson · Aug 17, 2016

Agree with the above but on different issue, if you have bugs...try to mount the flood light as far as reasonable from you. kt

k0ua · Aug 17, 2016

Lets discuss the reasons to use relays. One reason is because switches to handle higher currents can be more expensive that relays to handle that same current, but another good reason in automotive applications is because placing a relay closer to the source of power (the battery in this case) or the path from the source of power to the load (the lights in this case) can allow you to run a minimum amount of large wire and you only have to run a small control wire for the coil.

But when LED lights came on the scene, this changed up the thinking somewhat. They draw significantly less current than either halogen or conventional incandescent bulbs. Now it is possible to run fairly long supply and load wiring to the dashboard for switch control and back to the lighting without significant voltage drops and not needing wiring gauges nearly as large..

So long way around and complex answer for a simple question, but Yes you should be good to go without using a relay.

PILOON · Aug 17, 2016

Most toggle switches can handle 10 amps (quality ones).

As to fuses or breakers you always want to have protection as close to the battery as possible mostly to prevent shorting that starts fires.
SO, # 16 wire, better still 12 or 14 using a 10 amp protection (fuse or CB) will CYA, always as close as possible to the source (battery).
LED's draw so little amperage that any toggle switch can be used without a relay.
If the protection device cannot be near battery source just be sure that wire up to the protection device cannot short to ground (use protective sleeves and/or tie the wires off so that they can not chafe and short to ground).
Sleeves and grommets (in holes) plus tie wraps to isolate from metal works OK.
Just remember that fuses and CB's have to be the weak link in a circuit otherwise that wire becomes a heater element if it shorts to ground.

Headlights generally use a relay as the current draw is way over that magic 10 amp level but with LED's the draw is always below that 1o amp level.

KyleH · Aug 17, 2016

If you are replacing existing lights (or adding to a prewired oem circuit for halogen lights) with leds I wouldn't worry about a relay, but I like to use relays most of the time when adding lights (or whatever) because it can extend the life of the switches by reducing current passing through them. Each time a switch is turned on and off there is an arc, very small, but the greater the load the more damage it does each time, this normally takes a long time to add up to anything that would cause problems, but sooner or later the contacts will be blackened and not conduct as well, heat will build up and cause a failure. Switches are not cheap if you are going with oem style ones to match your tractor. For example I added two switches to my B2650 and used Kubota switches like the TLB models and they are around $55 each plus tax, so it makes sense to use a relay to reduce the current and extend the life of them as much as possible.

Also, spend the extra money to get weather sealed relays and connectors. I use Deutsch or weather pack and dielectric grease along with heavy wall heat shrink that has the glue to keep water out. Doing so can save a lot of headaches down the road by reducing the likelihood of corroded wires. As a mechanic, I've spent a lot of time tracing wiring issues and a lot of the time it's due to people cutting corners or trying to reduce cost, or my favorite is finding green spots where somebody probes the wires with a test light, huge no no these days as the copper is not like it used to be when exposed to the elements.

petegoud · Aug 18, 2016

I might take a little issue with the 'most toggle switches can handle 10 amps'. I've replaced too many '10 amp' switches that have failed when being used in circuits drawing 7-8 amps. Cheap switches perhaps. Relays are really the best way to go.

k0ua · Aug 18, 2016

petegoud said:
I might take a little issue with the 'most toggle switches can handle 10 amps'. I've replaced too many '10 amp' switches that have failed when being used in circuits drawing 7-8 amps. Cheap switches perhaps. Relays are really the best way to go.

A lot of the small toggle switches are just rated at 6 amps. One just needs to look carefully at the ratings and not work so close to the ratings.

Midniteoyl · Aug 18, 2016

The other, important, reason relays are used is to keep high amperage circuits out of the cockpit/cab. If a device malfunctions, or a short were to occur in a higher amperage device, the fire and smoke will be away from the user/driver.

Industrial Toys · Aug 18, 2016

No point installing a relay if it isn't required. But I would install yet another fuse, even though the circuit you are using is probably already fused.

As far as bugs go. A friend told me on the weekend that a Retrofit lighting contractor told her, that LEDs have the benefit of not attracting bugs. I told her, that the new LED light we installed in the garden seems to attract Bugs just fine. Is it a (color)temperature issue by chance?

Midniteoyl · Aug 18, 2016

Industrial Toys said:
No point installing a relay if it isn't required. But I would install yet another fuse, even though the circuit you are using is probably already fused.

As far as bugs go. A friend told me on the weekend that a Retrofit lighting contractor told her, that LEDs have the benefit of not attracting bugs. I told her, that the new LED light we installed in the garden seems to attract Bugs just fine. Is it a (color)temperature issue by chance?

rodnok · Aug 18, 2016

Short version: no, you dont need a relay for led lighting.

Industrial Toys · Aug 18, 2016

Interesting article. Funny though. They still claim that insects arn't attracted to Red, Yet we used to have all manner of problems with insects being attracted to the Red LED on smoke alarms, getting into the chamber and causing a false alarm.

Midniteoyl · Aug 18, 2016

Industrial Toys said:
Interesting article. Funny though. They still claim that insects arn't attracted to Red, Yet we used to have all manner of problems with insects being attracted to the Red LED on smoke alarms, getting into the chamber and causing a false alarm.

Bet you had more UV (blue) leaking through that red lens than you think.

TemporaryKubotaOwnerMark · Aug 18, 2016

rodnok said:
Short version: no, you dont need a relay for led lighting.

Depends on the LED lighting. For what the OP described, no. For some, yes. Depends on the current draw.

petegoud · Aug 19, 2016

Another thing one can do is actually measure the current used by the LED's. I use a Fluke 87, and have found that in some cases the actual draw in amperage was a little more than the stated draw on the LED's. That can make a difference if you're using a switch which is just barely rated in amperage. Another example of a good reason to use a relay might be if the wiring length could be shortened (a more direct route) instead of routing the wire to where it's convenient to use a switch. That said, the fastest, and easiest way to wire an LED is still probably a through a switch, just make sure it can handle the load.

ArlyA · Aug 19, 2016

I have to agree with Pete. You shouldn't need a relay for 2, low draw LED lights. But as Pete states, there is a large quality disparity in switches. When the manufacture states "10 amps" they are kidding. Where we use them, we commonly break the internal parts and then have a switch that does not go back to neutral. Not good for us. When we find one that can hold up to our hard use, they cost more, but we buy supply of them.

petegoud said:
I might take a little issue with the 'most toggle switches can handle 10 amps'. I've replaced too many '10 amp' switches that have failed when being used in circuits drawing 7-8 amps. Cheap switches perhaps. Relays are really the best way to go.

rodnok · Aug 19, 2016

Lets get real here. IF the wire is the correct size for the current draw and so is the switch a relay is not Needed. If the user is replacing incandescent lights with LED lights of the same lumens the wire that is present is more than sufficient. LED lighting draws approximaely 25% of the current than incandecent.

AJ197816134 · Aug 20, 2016

Great points made here, I just had to ask a friend who put a light bar on his tow truck why he has a 50 amp toggle switch, some ungodly looking 50's type of switch... It was a rotating bar lots of amps, I ran a continuous duty solenoid, and a 3.00 switch in his cab, LIGHTED mind I add. and he is still baffled...

I know some have spoke of small gauges of wires on newer machines, AMP draw is reduced, but correctly placed relays are more important...

TemporaryKubotaOwnerMark · Aug 21, 2016

rodnok said:
Lets get real here. IF the wire is the correct size for the current draw and so is the switch a relay is not Needed. If the user is replacing incandescent lights with LED lights of the same lumens the wire that is present is more than sufficient. LED lighting draws approximaely 25% of the current than incandecent.

Of course. But if you are adding new lights, you have to know the real current draw (as has been pointed out) and then choose your wiring, and switch or relay appropriately.

Just saying, "LEDs don't need relays." is wrong.