Driving light relays

[T_Diesel]

Would a horn relay be suitable for driving lights? I have concerns that perhaps they are not designed to support a continual current cycle ie in driving lights as opposed to a horn which is short current cycles.

Jaycar sell a range that say they are suitable for high current applications for about $10. Would I be best to get a light specific relay designed for continual current cycles?

[-Scott-]

I once bought a "horn" relay for a spotlight application, and the coil burnt out after about 2 hours.

Buy something rated for continuous duty.

[T_Diesel]

Thanks for that... Any suggestions on where to get a proper one?

[Micky-Lux]

Supercrap have them. How many lights and what wattage are you looking at running off the relay?

The reason I ask, is that they sell a cheaper one rated at 30A, which is fine for a pair of 100W spotties, I had it running 4x100W lights on the roof. The current was roughly 33.33A, which was marginally over what the relay was rated. The difference was something like $20 extra for the 40A relay. After a long night run, I managed to fuse the contacts together, meaning the lights wouldn't turn off. I've since upgraded to a 40A relay, with no problems so far.

[T_Diesel]

Supercrap have them. How many lights and what wattage are you looking at running off the relay?

The reason I ask, is that they sell a cheaper one rated at 30A, which is fine for a pair of 100W spotties, I had it running 4x100W lights on the roof. The current was roughly 33.33A, which was marginally over what the relay was rated. The difference was something like $20 extra for the 40A relay. After a long night run, I managed to fuse the contacts together, meaning the lights wouldn't turn off. I've since upgraded to a 40A relay, with no problems so far.

I'm only running 2 x 100W but the cheapy loom that came with the lights has melted and fused into the back of the 30A relay after prolonged use.

I want a beefier relay than 30A to minimise current / voltage drop and it saves upgrading it later if I get more lights down the track.

In terms of beefing up the wiring harness, I assume you only need to run a heavier guage from battery to relay, relay to lights and relay to ground?

[Micky-Lux]

If you use the 40A relay, you shouldn't have any problems. I think they also sell the relay holders too if your wiring is stuffed.

You should be able to just beef up the wiring from the battery to the relay, then the relay to the lights, and then from the lights to ground. I normally just run the negative from the lights to a convenient earth nearby (behind the bullbar?). The wire size on both sides of the light (positive and negative) should ideally be the same size. (That is, don't just upgrade the positive wire to your lights and forget about the negative, but I think reading your last post, you already know that).

On my roof lights, I have twin 6mm2 running up to them, the length of the run is about 2 metres back to the relay, and I've had no problems so far. I have 4 x 100W halogens running off them, so either 4mm2 or 6mm2, you should be fine with 2 x 100W. It's better to go bigger, as there's less voltage drop, and your lights will be brighter.

Hope this helps.

[drivesafe]

Hi T-Diesel, here’s two diagrams that might help.


For Negative switched lights





For Positive switched lights

[Micky-Lux]

only problem with those two diagrams is that in either case, you can turn them on/off with the high beam, or on permanently with the switch.

I think to be compliant with Qld Transport, you need to be able to isolate them altogether. To do this, in the top diagram, don't connect the yellow 2mm ground wire to the switch, or in the bottom diagram, don't connect the yellow 2mm 12v wire to the switch.

That way, they only come on with high beam, and if you have to isolate them (like when you don't want them on), you flick the switch.

I normally just run the earth for the lights to the chassis, but there's nothing at all wrong with running the earth back to the battery either.

Other than that, the diagrams are pretty much spot on as to how to wire it.

[stuee]

only problem with those two diagrams is that in either case, you can turn them on/off with the high beam, or on permanently with the switch.

I think to be compliant with Qld Transport, you need to be able to isolate them altogether. To do this, in the top diagram, don't connect the yellow 2mm ground wire to the switch, or in the bottom diagram, don't connect the yellow 2mm 12v wire to the switch.

That way, they only come on with high beam, and if you have to isolate them (like when you don't want them on), you flick the switch.

I normally just run the earth for the lights to the chassis, but there's nothing at all wrong with running the earth back to the battery either.

Other than that, the diagrams are pretty much spot on as to how to wire it.

Depends on what type of switch is being used. For switches that illuminate when switched on you require that third wire (yellow in this case) for the led/bulb in the switch. They are still an spst switch at the end of the day.

http://www.landyzone.co.uk/lz/attachmen ... itled1.jpg

The diagram does not state this but i assume that they would be for an illuminated switch as most people use these in spot light installations. (This is as opposed to a spdt switch which would allow the lights to act as you describe).

[T_Diesel]

Went to the auto elecs today to pick up a relay and some terminals. He suggested rather than running a 40W relay, run a 30W relay for each light and just split the signal from the switch to 86 on each relay.

I guess it really doesn't make that much difference, just a little more effort and expense I guess.

He also said he wouldn't be running 200W of light on a 30A relay and that the horn relay would have shat itself after a while as not designed for continuous load.

[chimpboy]

In terms of beefing up the wiring harness, I assume you only need to run a heavier guage from battery to relay, relay to lights and relay to ground?

Battery to relay, relay to lights, LIGHTS to ground.

[drivesafe]

I think to be compliant with Qld Transport, you need to be able to isolate them altogether.

Hi Micky, the switches are 3 position type, ON/OFF/ON, just not indicated in the diagrams

[Micky-Lux]

Went to the auto elecs today to pick up a relay and some terminals. He suggested rather than running a 40W relay, run a 30W relay for each light and just split the signal from the switch to 86 on each relay.

I guess it really doesn't make that much difference, just a little more effort and expense I guess.

He also said he wouldn't be running 200W of light on a 30A relay and that the horn relay would have shat itself after a while as not designed for continuous load.

200W @ 13.8 Volts = 14.5A. or at 11V (like stuffed alternator, flat battery) = 18A or thereabouts. Either way, a 30A continous rated relay should be fine. Running two isn't going to hurt things, but is overkill.

[Micky-Lux]

I think to be compliant with Qld Transport, you need to be able to isolate them altogether.

Hi Micky, the switches are 3 position type, ON/OFF/ON, just not indicated in the diagrams

Hey drivesafe

That makes sense in those diagrams. Probably something to be aware of more than anything, is that in the Qld Transport rulebook, it states that they should only come on with high beam. But it also states that as far as auxillary lighting goes, you are only allowed a maximum of four (4) forward facing lights, and they must be symetrical (mounted in pairs). I have 6, so technically not allowed. My last Zook had 7 (5 on the roof bar, 2 on the bullbar), so you get the picture. I've seen heaps of 4x4's getting around with more than 4 spotties. I've never been botherd by the police about them, I guess it comes down to how you use them.

I guess my point is, if you use the spotties correctly, don't abuse them by blinding oncoming traffic, and be sensible, I don't think you'll have any problems. You'd have to come across one angry copper on a bad day to get booked.

[drivesafe]

I have 6, so technically not allowed.

Hi Micky, this includes every ride I’ve own in the past 25 years, including 4 roof mounts on my 08 RR.

Only once was I warned about the roof lights and even then, this was at a random DUI stop in NSW and the copper who was testing me warned me to watch out for the sergeant running the DUI as he had a hatred for roof lights.

The laws are similar in all states.

I actually manufacture headlight and driving light wiring upgrade kits and did a fair bit of law checking over the years to make sure my kits and their instruction didn’t get my customers in any trouble.

[T_Diesel]

Went to the auto elecs today to pick up a relay and some terminals. He suggested rather than running a 40W relay, run a 30W relay for each light and just split the signal from the switch to 86 on each relay.

I guess it really doesn't make that much difference, just a little more effort and expense I guess.

He also said he wouldn't be running 200W of light on a 30A relay and that the horn relay would have shat itself after a while as not designed for continuous load.

200W @ 13.8 Volts = 14.5A. or at 11V (like stuffed alternator, flat battery) = 18A or thereabouts. Either way, a 30A continous rated relay should be fine. Running two isn't going to hurt things, but is overkill.

It might be overkill, and you could reall get technical and add voltage drop into the equation aswell!

Either way, the loom that was supplied free with the lights when I bought them melted to a plastic pulp after prolonged useage so I aint taking any second chances.

I've now got two sets of 25A wire and two 30A relays individually fused running to the bull bar which aint necessarily a bad thing. My cost to make these two looms properly with heavy duty cable, connectors, heat shrink etc, was still less than the RRP on the shitty loom supplied free with the lights.

[Micky-Lux]

Hi T_Diesel..

Yeah, generally when you make your own looms it works out cheaper. And generally when you make your own looms, it usually works out better anyway as you can get the lengths right, and use good quality parts. I think when it's for yourself, you tend to take the time to get it right, whereas a generic loom is made for a broad range of vehicles at a cost.

Anyway, it's a hell of a lot better to over-rate everything, than to under rate something, as you've already found out. I don't think you'll have any problems with your current setup.

Cheers

[T_Diesel]

Hi T_Diesel..

Yeah, generally when you make your own looms it works out cheaper. And generally when you make your own looms, it usually works out better anyway as you can get the lengths right, and use good quality parts. I think when it's for yourself, you tend to take the time to get it right, whereas a generic loom is made for a broad range of vehicles at a cost.

Anyway, it's a hell of a lot better to over-rate everything, than to under rate something, as you've already found out. I don't think you'll have any problems with your current setup.

Cheers

I finished it off last night and me thinks that the heavier loom has made the LF's a lot brighter. Next upgrade will be to HID them!!

[phippsy]

Just a question on upgrading a loom etc, on the relays would it be better to solder to it's terminals or just use crimp spade connectors?

[macca81]

Just a question on upgrading a loom etc, on the relays would it be better to solder to it's terminals or just use crimp spade connectors?

if you have a good quality crimper, then i believe that crimping is the best way to go. but if you just have a generic crimper, then solder it.

solder, i have found, tends to be more prone to cracking and coming apart under severe vibrations. the amount of times iv had to fix my mates soldering jobs when he re-wired our buggy... and the ones he crimped he used a cheap crimp tool... with my ratcheting crimp tool, there is no way a person can break the connection by pulling on it...

[phippsy]

thanks for that, I've got a good ratcheting crimper so all's good.

[stuee]

Just a question on upgrading a loom etc, on the relays would it be better to solder to it's terminals or just use crimp spade connectors?

if you have a good quality crimper, then i believe that crimping is the best way to go. but if you just have a generic crimper, then solder it.

solder, i have found, tends to be more prone to cracking and coming apart under severe vibrations. the amount of times iv had to fix my mates soldering jobs when he re-wired our buggy... and the ones he crimped he used a cheap crimp tool... with my ratcheting crimp tool, there is no way a person can break the connection by pulling on it...

What can one expect to pay for a quality crimping tool? I solder my connections as i only have a crappy generic crimper. Also where would be a good place to pick one up?

[RV80]

Any tool shop that sells Kingchrome(this is what i have and it works good) gear will have them. 50 bucks or so they should be.

[Micky-Lux]

Or the Cabac ones. Haymans or Ideal sell them, but not sure of the $$$. I think the ratcheting ones are more or less the same (with a few exceptions) provided you set the tension right.

[macca81]

mine cost about 60 bucks. forget what brand, bought it from an auto lecky suplies place