How to bench test horn?

[m3a1]

Ok, this is something that gets everyone confused from time to time so there's surely no dishonor in it.

Think of your truck's batteries as being set up something like those big D-cell batteries in your dad's old flashlight (the one every dad kept by the top of the basement stairs, or on top of the the fuse box).

Those D-cell batteries were stacked one upon another, right? They were connected with the positive terminal at one end of the stack in contact with the flashlight and the negative end of that stack of batteries in contact with the flashlight. But where the batteries touched one another in between it was negative touching positive. In other words...a series of batteries which is why this arrangement is referred to as being In Series. That is exactly how we achieve 24volts with two 12v batteries.

So, to test your horn you are going to attach a wire from the positive lead (the one that goes to your truck) and attach a wire from the negative lead (the other one that goes to your truck). Ignore the battery terminals where the short cable is connecting the two batteries. Do that and you'll have one wire for each contact on the horn and 24volts.

Carry on!

Cheers,
TJ

[D Pizzoferrato]

Like TJ said. He conveys the English language better than I do. Two terminals on the horn. 24VDC Positive (Battery) to one terminal; 24VDC (Battery) Negative to the other.

[mutt and jeff]

Well, I guess I got three dead horns. . . for now. Looked at a wiring diagram and it showed one of the terminals being ground, so the other must be hot. So I hooked up my test leads to positive and negative off my MUTT batteries and clipped them to a 24 v head light bulb and I got light, then I touched them to the horn terminals and then reversed them when I got nothing and I still get nothing on all three. So I've answered the bench test question and discovered I've got three dead horns . . . for now. Gonna open them up and play with them and see if it's something I can fix.

Another think I learned is that 24 volts sure creates a lot of spark. I'm used to 6v on the WWII stuff. This 24v stuff will arc weld a battery clamp from a positive battery post to a hold down wing nut. Don't ask me how I know.

Thanks to all who assisted.

[m3a1]

ARC WELDING Merit Badge awarded!

[rickf]

24 volts is the top end of the the standard welding voltage on most welders. That is why it is possible to weld with a couple of batteries. controlling the amperage is a bit tricky though. Dead short circuit amperage is over a thousand amps!!!

[mutt and jeff]

There is a trick to remagnetizing a Model T magneto using three 12v batterys connected in series. It takes 36v to do the trick. Some guys actualy use their welding unit. We pulled all the batterys out of our family cars and melted a few jumper cables until we got the connections correct. Then touch to the pick up magnet when the compas reads N. So, these little car batteries can generate some umph.

[D Pizzoferrato]

When working around 24 VDC, always disconnect the batteries; Negative lead first. In case you forget to disconnect your batterieis, never wear any wedding rings (or other rings) when wrenching around 24 VDC stuff. A wrench shorted to a live circuit and touching your finger bling will leave you a permanent reminder with the smell of burning meat. No, I've never done it, but learned to respect the 24 through my many years of heavy construction equipment experience back during my misguided youth.