Horn motor dropping resister

[Jon-Ohio]

For a horn motor - What size power resister is needed to drop 12V to 7V(not 6). The motor draws 7.2 amps under load ?

thanks for any help on the mathematics

Jon in Ohio

[crock]

I purchased an adjustable resistor ohmite #588-d100k2reo 100wat, 2ohm 10%. Ordered from mouser electronics www.mouser.com works just fine.

[marc hildebrant]

Originally Posted by Jon-Ohio

For a horn motor - What size power resister is needed to drop 12V to 7V(not 6). The motor draws 7.2 amps under load ?

thanks for any help on the mathematics

Jon in Ohio

Ohms law : V=IR

V in volts, I in amps, and R in ohms.

Marc

[nstegall]

Jon,

The best way to solve your horn problim is to have your horn rewound for a 6 volt system. These voltage dropage units, as a rule are no more than a bandaid fix.

Regards,

Neil
THE HORN MAN
601-469-0878
[email protected]

[steve s]

Originally Posted by marc hildebrant

Ohms law : V=IR

V in volts, I in amps, and R in ohms.

Marc

Just to clarify what Marc said, the relevant voltage in this case is the voltage DROP that you want the load resistor to accomplish. So, if you want 12 volts dropped down to 7, that's a drop of 5. Or, if your alternator is humming along at say 14 volts, that's a drop of 7. In practice, I suspect that anything around 1 ohm would work fine.

[Mike V. Florida]

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Why 7?

[Richard in NC]

Some people use the primary winding of an old ignition coil for the resister. Mount it in the frame where it won't be seen.

[mrtexas]

Originally Posted by Jon-Ohio

For a horn motor - What size power resister is needed to drop 12V to 7V(not 6). The motor draws 7.2 amps under load ?

thanks for any help on the mathematics

Jon in Ohio

Why not buy one of the nice resisters the usual suppliers sell that has fins on it for cooling? About $20.

[Jon-Ohio]

Thanks for all the info. I'm going to try and get a 1 ohm/ 50 watt resister at a local surplus electronics store and see if that works.

Jon in Ohio