I purchased a quantity of Model T parts that include a box of horns with no markings on them.
How do I determine the difference between a Magneto Horn as compared to a Battery Horn without causing damage to them. Unfortunately they are currently in a storage unit so pictures are not a option today.
Thank you in advance for assistance,
Magneto horns will have two electrical terminals.
Look down the mouth of the horn. If you see an adjusting screw in the center of the diaphragm it's a mag horn.
Magneto horn, tiny cover.
Battery horn, large cover.
Adjusting screw and mechanism cover size are basic clues.
There are also several differences (not only manufacturer) in magneto horns depending upon what year car they were originally installed upon. These differences turn on how the horn button was implemented. Some magneto horns can easily be modified to work on different year Model T's.
Thank you Bob, Steve, Dan, Ron and MTFCA.
This parts changer, not real mechanic, appreciates the help.
Have a great day,
I feel I must correct one thing here. Early T magneto horns have 2 power connections and these CAN be made to work on later T's by simply connecting one of the 2 connections to car negative ground. Ford used this during transition to the single connection mag horn. He simply removed one the fiber insulating washers on one of the connections and thus that connection was then connected to the horn body and thus grounded. Later magneto horns have only a single connection just like the battery horns have. In those Mag horns the ground is made internally to the horn housing and thus the other electrical connection parts are removed and the horn is then cheaper. Thus you should not assume that a horn is not a magneto horn based upon the electrical connections being one or two terminals. The best ID method is Steve Jelf's method namely to look into the snout of the horn and if you see a screwdriver slot and lock nut in the center of the diaphragm then for sure you are looking into a Magneto horn. If you DO NOT see that adjuster down in there then you are NOT looking down into a magneto horn. Mag horns are supposed to be adjusted for maximum loudness when connected to a "TEST GENERATOR" (not defined but probably an HCCT) but the current should not exceed 2 amps AC. If the mag horn sounds particularly bad then you probably have it adjusted perfectly. If adjusted wrong the horn button can be used as a kill switch.
Hope this helps.
Thanks for chiming-in. Once again you provide sunlight on a cloudy issue for the uninformed.
Keep it up buddy,
If it's a working horn; magneto horns go thunk when applying 6 volts, battery horns make a sick goose sound. Not that one might sound more dreadful over the other, but a sweet Model T sound for sure.