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Discussion Starter · #1 ·
Hi folks
Iv'e taken off the standard headlamp and replaced with a nice 7 inch lamp and added a spotlight. I'm running a hid in the spotlamp and was wondering if anyone knows if the standard switch will handle 75 watts? I intend to use the low beam position for the headlight and the high position for the hid which will be 75 watts. Any ideas would be appreciated.
Kranski.???
 

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It is not so much the watts of the bulbs that matter, it is the amp draw you want to run through the switch.

You can run an HID kit through the switch on the stock fuse, but much past there and you will blow the fuse.

So, assuming the extra spotlights are drawing more amps than the headlight fuse can carry, just use a relay to run the spots and they will get their own fuse.
 

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Discussion Starter · #3 ·
hid lights

Thanks Square Rounder.
So if the headlight fuse blows then I need to use a relay, am I understanding that correctly?
Kranski
 

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Thanks Square Rounder.
So if the headlight fuse blows then I need to use a relay, am I understanding that correctly?
Kranski
In short, no, it won't work as you've described. But it's not because of the fuse. This is probably more information than you want, but should give you a better understanding:
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1) As per the service manual, the factory fuse ratings are 10A for HI/LO beam. However, the way it is wired, there is only ONE headlight relay feeding either the high or low beam circuit. The dimmer switch merely directs the power to one (and only one) of the two fuses, for either the high or low beam, respectively.

Everything I can find on the headlight relay (p/n 38740-24A00) shows it rated at 12VDC/5A. So, without further information, it looks like you have a 5-amp limitation on the factory headlight relay, and thus the circuit you're wanting to create.

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2) The factory low-beam filament is 55 watts. So, 55 watts / 12.5 VDC = 4.4 amperes. For the high-beam, that'd be 60 watts/12.5 VDC = 4.8 amperes. Either beam, by itself, falls within spec of the factory 5A headlight relay.

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3) Most aftermarket HID bulbs pull about 3 amps once in steady state, but there can be as much as 7 ~ 7.5 amps at startup to get the bulb ignited. That is the purpose of the HID ballast, to regulate current in such a decaying manner. That translates to about 90 watts peak (at startup) down to around 37 watts nominal, just to power the HID light @ 12.5 VDC.

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So, your wattage estimate of 75 watts is inaccurate. You're actually looking at more like 145 watts at startup and 90 watts steady state, total, for both lights.

Again, from what I can find, the factory headlight relay is a 5 amp relay, so despite splitting the load between two 10A fuses, you'd likely fry the relay the second you turn everything on (with 11+ amps total at startup, dropping down to around 8 amps once the HID reaches steady-state).

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That said, I agree with Square Rounder that you must run an additional relay(s). Not only will this handle the additional load, but it also functions as an automatic on/off switch -- unless you want the capability of turning the spotlight on with the bike turned off.

For instance, you could use the stock wiring/relay for the stock halogen headlight, but then add a second dedicated relay for the HID. You can pick up automotive relays capable of handling 30A at most local automotive stores, and 14-16ga wire would be sufficient for the amperage requirements (larger wire would better handle the HID current spikes). Throw in a weatherproof 10-amp inline fuse for the HID circuit near the positive battery terminal, and be sure to place all ground connections at the grounding bolt on the rear jug (to prevent grounding loops).

How you wire it really depends on how you plan to use the spotlight. You also have the option of using two new relays, and essentially using the factory relay as a relay trigger alone (with no lights/load on the factory circuit).
 
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