2002 F100 No Warning Sounds, Lots of testing completed, still no answers, maybe ECM?

[mcpedersen]

Hello All and thank you in advance for your help!

I have a 2002 F100 Four Stroke and am not getting any noise at all out of the warning speaker under my console. I turn the key on and get no noise, if I pull the kill switch out, still nothing. The horn does sound when I connect + and - to it directly, or if I provide ground to the pink side with the key on.
I have tried removing the temp sensor and heating it up while it was plugged in. I have tried jumping across the temp sensor connector. I have also tried grounding each side of the connector individually.
If I provide ground to the pink lead (lowest and forward most pin) on the connector for the ECM I get sound from the horn.
The power head was replace a couple of years ago if that makes a difference.
While messing with it today, I got a quick chirp out of it while the engine was turning over, but never got anything else.
I really want to solve this problem so I can keep it all stock and not have to add any aftermarket temp guages etc.
Thanks
Mike

[boscoe99]

What makes you think that you have a problem?

Single engine Yams never sound the horn when the key is turned on.

Some Yams, but not all, will sound the horn if and when the starter motor is engaged with the kill switch activated.

To test the over temperature warning system disconnect the connector to the thermosensor. Get a 220 ohm resistor from Radio Shack and jumper it between the two wires that are in the connector. Start the motor. Let it idle for about a minute or minute and a half. The horn should sound and if you have a multi-function tachometer the over temp icon should start to blink.

To test the low oil pressure system disconnect the connector to the oil pressure switch. Jumper the wire in the connector to a ground on the block. Start the motor and let it idle for half a minute or so. The horn should sound and the icon above the oil pot should start flashing.

[rodbolt17]

if you hooked up the horn directly to battery voltage and it did not sound, bad horn.

[mcpedersen]

Thanks, I will try both of those when the rain here stops and let you know how it went.