MTFCA Forum

Ok, why is the speed of the engine affecting the pitch of my motor type horn? I assumed that it was getting power from the battery which would be constant. Would it have to do with me changing my generator cutout to a diode?

If you have a motor-type battery horn, the horn's motor speed will respond to an increase in the system voltage resulting from the generator charge rate increasing with engine speed. It's probably normal, assuming your battery is in good condition and your generator's charging rate is adjusted properly. With the engine off, or running at idle, the system voltage will be very close to 6 volts. As engine speed increases, the generator output will increase and the system voltage will climb above 7 volts and may reach 8 or 9 volts. A weak battery or horn motor that needs service will cause the system voltage to drop more than normal when the horn is operating and the engine is idling or stopped. Using a diode should have no significant effect. It's common for the heater blower motor in many vehicles to speed up when the engine speed is increased.

Hmm .. interesting. Yes, as I mentioned it’s a motor type horn. The battery is new and the generator is adjusted to out put no more than 3-4 amps. Just never had a fluctuation when I had the Fun Projects VR installed.

An actual Voltage Regulator will limit voltage fluctuations resulting from the normal variations in generator output caused by changes in engine speed.

A simple diode or a stock cutout relay will not regulate voltage or current.

A voltage regulator will function like a governor for the generator's output.

A diode or cutout behaves like an automatic on/off switch.

Ok … that’s what I was thinking. I had only had the VR in the car since I first got it on the road. Mystery solved. My previous T was a non starter type and had a magneto horn that was all over the place in sound! Thanks.

Mark Osterman wrote: ↑

Thu Mar 23, 2023 12:08 am

Ok … that’s what I was thinking. I had only had the VR in the car since I first got it on the road. Mystery solved. My previous T was a non starter type and had a magneto horn that was all over the place in sound! Thanks.

And what did you do with the Fun Projects VR? Like to see it

I'd like to hold the fun projects regulator in my hot little hand, if you have no further use for it!

Allan from down under.