Horn wiring diagram needed

Tiny
HAROLD BOHLIN
  • MEMBER
  • 1990 FORD F-450
  • V8
  • 2WD
  • AUTOMATIC
  • 200,000 MILES
Need horn wiring diagram so I know what wires to check for nonworking horn.
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Monday, August 27th, 2018 AT 11:30 PM

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Tiny
STEVE W.
  • EXPERT
Welcome to 2CarPros.

The horns are grounded to the body through the mounting bolts and the yellow with light green wire provides power to them. If you have cruise control the wiring uses a relay to trigger the power to the horns, if you do not have cruise you do not have a relay. On the models that do not have a relay there is a jumper block that plugs into the wiring where the relay normally goes.
Easiest way to test would be to connect a high draw test light (headlight bulb works well) in place of the horns. That way you can test if the circuit can carry enough current to make the horns sound. A normal test light does not provide enough draw to be sure.
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Tuesday, August 28th, 2018 AT 10:18 AM

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