JeffTsai

iTrader: (1)

Any harness kit is usually comprised of the same parts. If both are reputable companies, pick the cheaper one.

Also, there is no need for a dual relay. The commonly used automotive relay for this application is a 12V 30A relay (most of the time the Bosch brand). This works out to 360Watts for one relay. Considering that each HID uses about 40-50watts(35W at the bulb, but there is the power conversion inefficiency of the ballast you have to factor in) at operational state, and 100-150W at the VERY MOST on the few seconds on startup....if your HID's are pulling more than 360W then you have some serious problems to worry about .

Dual relays can handle 720Watts. Is there a use for that? I think its for you to decide.

GS300Rich

Great info Jeff. I have just been reading what people are writing, about how it is better to have a dual relay. My problem is that whenever I turn the headlights on sometimes both HIDs fire up, sometimes only one side fires up, usually the passenger side, and then if I turn the headlights off and then on again sometimes neither will fire up. If I turn the lights on to go to the store, when I leave the store and start the car again most of the time only one light turns on. Another member has given me some ideas that it may be the connection to the battery or the relay, and I think I am just going to play it safe and just order a whole new harness. Any thoughts on my problem?

JeffTsai

iTrader: (1)

GS300Rich, first of all...I'm assuming you have an aftermarket HID system. OEM ballasts shold never have this kind of problem even on the stock harnes since they have a very wide range of voltage acceptance. If I'm correct in you having an aftermarket setup, are your ballats hooked up directly to the car's stock harness? If that is the case, it is a good idea to install a relay harness to the battery. A single relay will work just fine if the harness is built correctly.

When I say built correctly, I mean correctly sized wiring. If the wiring is too thin for the intended power level, there will be increased resistance when the ballast first starts. Kind of like pushing a water tower's whole tank thru a 1inch diameter pipe rather than the 5ft dia pipe. When both ballasts pull power, the voltage drops because the stock harness is not thick enough to carry the juice(think of 10 houses trying to tap off that 1inch pipe, theres not enough water to go around). A dual relay harness will do the job with two sets of thin wires rather than one set of correctly sized wire on a single relay setup. I hope I don't sound too confusing here.

Having a single or dual relay has nothing to do with it lighting up or not. As I mentioned a single relay will carry 360W, your problem is the wiring. I'm willing to bet the car's stock relay can handle the power, its just that the wiring itself is too thin. If you upgraded the stock wiring, it would probably work just fine, but thats way too much work since that will involve digging thru the dash and firewall. So just install a harness and your problem should go away.

GS300Rich

I have a wiring harness already installed, and I am using philips ballasts. I know the line running to the battery is a 12G line, not sure the rest of the harness as it is wrapped with insulation/ weatherproofing materials. I am going to order a new harness from one of the sites to see if that is the problem.