Headlight wiring voltage drop

[tonywiddows]

My SUV has about 0.5v total wiring voltage drop to the headlights. The (factory) wiring looks about the thickness of a human hair I am thinking of adding suitable relays to get rid of most of the drop. Can anyone tell me whether the additional brightness obtained will (a) be noticeable and (b) shorten bulb life significantly ? Or are bulbs designed to accommodate this order of volt drop in the loom?
.............Tony Melbourne Australia

 

[JRW261]

To see if it will be any brighter, test the lights by directly hooking them to the battery with a jumper wire... if you notice any difference you will know your answer.

I think it would be more work than it is worth unless you have trouble with wiring getting hot and melting. But its worth a try.

 

[Womprat]

Don't forget to go through the ground system. The connectors get neglected and corrode and build resistance where they bolt to the frame etc. I don't know about the Australialn models but Made in USA vehicles are famous for having long paths to the lights and many of the the light swithces had circuit breakers in them which is another area that can cause resisitance. Headlights are about 55 watts so you can see how much current is necessary. My limited experience says do it. Here is a trick you might use, hook any auxilliary driving light relay to the bright circuit. You only have one switch to hit to shut them down.
Womp

 

[tonywiddows]

Thanks folks. I guess my question is more about whether in the design of vehicle electrics, a loom drop of 0.5v is normal for headlight circuits, and whether bulb design caters for the normal battery potential variations. The truck is new.....Tony

 

[Doug020668]

Tony, 0.5 volt drop is excessive. New vehicles may have neglible drop in the wiring, switches & connectors etc, but as they undergo ageing, the situation worsens. I would go the whole hog in this one, upgrade the wiring to the lights, fit circuit breakers & relays, renew the head lamp plugs, and ensure that all connectors are soldered. Blade terminals are good for about 15-20A max, so if your current draw is approaching that limit, either go for a screw terminal relay, or split the circuit into two circuits, say make high beam into left & right high beam. That way you have some redundancy and dont overload the connections. in my experience, relay contacts in a quality relay will take a load all the way up to their rating, but the connections are the weak link as surface area of the crimped connector socket tends to be limited and this causes heat to be generated through limited contact area causing a high resistance. if you must use crimped and/or soldered terminals,use harder brass ones rather than soft copper crimps as copper tends to lose its tension as it heats up and the amount of heat generated by a 15A current through the avaerage crimped connector is considerable, enough to looosen it and exacerbate the problem. I do this stuff for a living and I've seen a good bit of this sort of thing. I adopt the above approach and i never have these problems.

Yes, you can use the "Premium" type globes, but all that does is sort of hide the problem, and delay its onset. If you use the "premium" globes after you have completed the mods, you will get your money's worth out of them, especially if it means you dont have to upgrade your alternator to obtain brighter lights.

Doug

 

[tonywiddows]

Doug, thanks for this advice and practical solutions. As this vehicle is nearly new, I will first query with Toyota if there is a fault under warranty if 0.5v is excessive.
Tony

 

[Chancy99]

Be careful about high currents though if you go with higher-wattage bulbs. I've seen a 9006 (9004?) high-beam plug half-melt when using 100W high-beam bulbs.

Dean.

 

[tonywiddows]

Dean, I agree, also can melt the polycarb headlight enclosures. Whole issue here is a new veh with apparently excessive v drop. 55w bulbs should be adequate if the wiring gives them half a chance !..........Tony