Blowing brake light bulbs

Andrew Summerville /

1978 Honda Hobbit PA-II. Ordered some missing bulbs (and other goodies) from Treats and the brake light bulb blew in less than a couple minutes. Headlight works only on low beam (I'm currently looking into the many options to fix/upgrade this on this forum) and the horn works. I noticed the resistor behind the horn wasn't plugged in and I'm not sure if the speedo or high beam indicator bulbs are present/working yet.

Did the bulb blow because the resistor wasn't plugged in

Or maybe my rectifier is bad?

Or because I might have been trying the high beam (which must be burned out) and the other bulbs weren't present so it was taking the brunt of the voltage?

I'm going to check the voltage at the light socket when I have an extra set of hands soon (that should tell me if the rectifier is at least doing its job I think). I don't want to throw a ton of bulbs at this since they are hard to find and not exactly "cheap" if they keep blowing out.

On that note, if my voltage/rectifier is good and I find some LED replacements would they do ok in the tail/brake and speedo/hight beam spots? Or will that cause too much current to the headlight bulb (which I'm leaning toward upgrading to the 25w/25w replaceable bulb assembly anyway - so a little extra juice shouldn't hurt it)

I am also reading that these rectifiers (31700-166-008) are 12v, but the bulbs throughout the system are all 6 volt, so is the rectifier only really there to convert AC to DC since the regulation function could allow too much voltage for the bulbs? If this is the case can/should I upgrade to 12v bulbs to prevent them from blowing out as much?


Re: Blowing brake light bulbs

A '78 hobbit doesn't have a regulator, just a rectifier.

That said, something is definitely wrong if you're blowing bulbs on a completely stock setup.

Replacing your bulbs with LEDs will result in more current going through the remaining non-LED bulbs, without a regulator. That said, LED bulbs are awesome and much brighter, so I recommend them, just get one of these too:

Re: Blowing brake light bulbs

And yeah, that resistor is in the headlight circuit (in parallel with the "low" light filament), so if it is not connected you could be overloading it.

Re: Blowing brake light bulbs

Andrew Summerville /

Awesome thanks! If I get that regulator I can switch to LEDs? I'll look for explanation on how to hook it up on the forums, thanks!

Re: Blowing brake light bulbs

Depends on the bulbs. Some will work with with AC, some will need rectified DC. The rectifier in the the hobbit is weird, and not on the lighting circuit (except for the ground on the taillight bulb? Weird).

Re: Blowing brake light bulbs

Andrew Summerville /

That could explain why the tail light bulb didn't blow lol. Still trying to find some instructions on where/how to install this 6v regulator. Treats has a very general "tutorial" on the product description, but I found a video on YouTube that may have guided me. Looks like I can hook the regulator up to yellow wire from stator (headlight and tail lights) and the green/yellow (brake light) to have my bulbs running on regulated current? Or do I hook up the regulator to the yellow (as above) and the red (brake switches)? My guess is the latter as this would supply regulation to the whole lighting circuit. I could combine both the yellow and red wires to the input on the regulator and then combine to the output as well on the other end?

Re: Blowing brake light bulbs

I suspect that you will need one regulator per circuit; I see there are multiple lighting coils and I'd bet that they're out of phase. Do not combine these circuits as you'd basically be shorting out your coils.

Yellow wire from the stator powers the headlight high/low filaments, tail light, speedometer bulb, and the high beam bulb

Red wire from the stator powers the brake light, and the horn

Green wire from the stator is the return for both lighting circuits

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