Help on 8volt system and burnt indicator bulbs

paulrhd29nzpaulrhd29nz Posts: 179Member
All, my new 51 C6CC came with an 8 volt electrical system. It has a modern converted single wire alternator that puts out the correct voltage for the 8 volt battery. My problem is that I can't keep the turn signal bulbs from blowing after a few uses.
There is no problem with brake lights,running lights,interior lights,radio, gauges, heater, headlights ( in fact the headlights are better than my 90 Dodge truck!) The 308 motor starts incredibly well hot or cold and it has a petronics ignition installed in it as well. Today I open up the voltage regulator for a look see and it looks like its only purpose now is a junction box.
The single wire from the 8V alternator goes the the Battery terminal side of the regulator. The "F" terminal is empty and there is one 10g wire coming from the "A" side of the regulator going in to the main wire loom that goes into the cab. ( I'm going to assume this goes to the Gen idiot light)
Do any of you and your infinite amount of wisdom and knowledge have any advise as to how I fix my indicator problem?
It should be noted that that I'm using the correct bulbs rated at 1154 (made in China )


  • paulrhd29nzpaulrhd29nz Posts: 179Member
    I forgot to mention, yes I replaced the flasher.
  • Jon BJon B Posts: 6,839Administrator
    I'm not an electrical specialist, but the 1154 bulb is rated 6.4 to 7 volts. Wouldn't 8 volts shorten the life?

    Have all your other lamps and electrical components run for long periods of time without blowing out? If so, then possibly they are rated for at least 8 volts.

    Anyway, that's my theory!
  • GeoffGeoff Posts: 3,538Senior Contributor
    Go back to 6 volts and use an Optima battery.
  • GeoffGeoff Posts: 3,538Senior Contributor
    The initial voltage surge is usually what blows a bulb. This is amplified with the on/off repeat of the indicators. Murphy's Law - All improvements will have an inverse effect on reliability. You may be able to get 8 volt rated bulbs, but you are heading outside the parameters of reliability.
  • charles4dcharles4d Posts: 470Expert Adviser
    Would an (Led) light emitting diodes work?
  • LanceLance Posts: 744Member
    If you're using an 8 volt battery, you better reset your voltage regulator as well. It is not rated for 8 volts only 6. In time it will burn up.
  • 50C8DAN50C8DAN Posts: 1,747Senior Contributor
    Lance I believe he is using an internally regulated alternator, so the external box is just for show?
  • LanceLance Posts: 744Member
    Yeah you're right Dan. Eight volts is just trouble . Leave it 6 or go to 12 and do the whole system.
  • Ken U-TxKen U-Tx Posts: 3,605Senior Contributor
    Paul, a simpler solution would be to try a .8 ohm ballast resistor in the power feed to the flasher relay. This will drop the measurable voltage going to the front and rear bulbs on each side to approximately 6-7 volts depending on the 8V alternator output. There are some ignition coil ballast resistors in this .75-.85 Ohm range .
  • Ken U-TxKen U-Tx Posts: 3,605Senior Contributor
    edited November 2018
    The above is based on standard incandescent 6.4 V 1154 dual filament bulbs with 2.63 amp draw in the brighter stop/ turn filament. @16 watts. Since there are two bulbs working on either side when turn signal switch is on, the amps draw is 5.26 amps. To figure the resistance of the two filaments we divide the rated voltage by the amps, thus 6.4/5.26= 1.2 ohms. If we used a 1.2 ohm resistor, then the 8V supply would be cut in half to 4V, which is too much of a drop, so we need a smaller resistance of around .6-.8 ohms to get desired 6-7 volt range at bulbs.

  • paulrhd29nzpaulrhd29nz Posts: 179Member
    Ken , thank you very much. That’s the kinda solution I was looking for. 
Sign In or Register to comment.