Headlights keep blowing

[Samargh]

Curly electrical one for you guys..

Front headlight bulb keeps blowing (both dimmed and full) on an 86 spree. replace the bulb and its gone within 5 seconds.

rear lights are fine. Everything else seems to be going OK.

any clues where I can even _start_ troubleshooting this one (without the need for a small mortgage to pay for replacement bulbs)?

Will introducing an in-line resistance to the front circuit choke down the current to stop the bulb from blowing, and if so, what resistance value and power rating should I be looking at?

TIA

Dave

[mousewheels]

Here's a schematic from the Spree, ignore the magenta markups - that's measurements from a bad regulator



If you have a multimeter check (AC) volts at the regulator for the White wire to ground and Yellow wire to ground. The Yellow should read lower than the White to gnd, and under 14.5v or so (check the service manual)..

--Edit - was just looking at the Spree manual, they don't spec the headlight voltage.

Since you are blowing headlights very fast, I'd guess the volts are way over 15. If this scooter is new to you, there could be a chance someone got the Yellow and White wires crossed up at the stator.
-- End edit


I am guessing the reason the headlight portion of the stator is brought to the regulator is there is a voltage limiter (clamp) inside the regulator. If this is blown (or open) it could result in an overvoltage on the headlight circuit.

---
Putting a device in series with the coil does not look to the be best solution, if the headlight switch contacts open between low/high beam, you may blow the high beam and instrument lamps. That is - a resistor in series sized to keep the headlight from blowing would still be too small to protect the little lamps.

But if your regulator is bad open on the "Yellow" terminal, you could add an external clamp (MOV, Tranzorb or something similar as a voltage clamp)

[noiseguy]

Are you running a battery in that scooter?

[Samargh]

Yep, running a battery but it doesn't charge properly. I know I've got some nasty electrics on the beast, but the main lights have always worked. It wasn't until the bulb bl;ew and came to replace it that I even realised it had a dimmer on it (yeah, I know... still pretty knew to scooters and this is a modified spree, brought out as a nifty fifty direct from Japan. Theres a few other differences between it and a standard 86 spree).

Just went to get some new bulbs, and checked on the cost of a replacement regulator/rectifier... does $150US sound about right????

If I had a circuit diagram of the internals, I'd be inclined to component build a replacement....

[Kenny_McCormic]

$150 is * up.