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Horn problem-always on, may involve steering wheel
Hi-looking for advice. I have a 73 F100 RWD. I assumed the wiring is stock, but it is equal parts electrical tape and wire.
The problem- my horn relay is always on. The plug to the relay indicates yellow and blue (power and horn switch) are coupled. The relay opens if I disconnect the steering column plug. I have checked at the truck end of the steering plug-the blue wire is hot. When plugged in, the little brass button on the steering hub is hot. The relay opens when I remove the steering wheel.
Thus I think the wheel is the problem. I have a turn signal cancel clip installed. I think it is touching something and grounding the horn. Pic attached. Is this the correct cancel clip? I can trim it, but want to know if it is installed incorrectly. I also don't know if the wheel is correct. I can find little information online about that part.
Any other suggestions? I do not have a rag joint ground strap either (who knew!).
Brass button is hot Cancel clip sticks down and touches the silver plated on the turn signal switch. Why?
Mismatched parts.
First, never seen a cancelling cam sit that proud of the flat surface before. Are both the steering wheel and cam original and from the same application?
Second, you've got the wrong turn signal switch for the steering wheel. Or vice versa.
See how the turn signal switch has only one copper contact? And see how the steering wheel has two separate copper traces?
The wheel is for an application where no relay is used, and power comes up one wire, through one contact, then out the other and on to the horn directly.
The switch is the type used with a relay and simply grounds to the column when contact is made by pushing the horn button.
Or something like that...
But definitely mismatched parts.
Have you found the relay under the hood? Not sure where it was on a '73, or if every truck got them.
In '79, you could get pickup trucks either with, or without a horn relay. I forget if the reason was gauges vs lights in the dash, or A/C vs no A/C, or what. But my '79 F350 did not have a horn relay. So I added one after having had other trucks without them and much preferring a horn system with a relay.
1978/79 2 spoke steering wheel, T/S switches and horn pads are different than 1971/77.
1978/79's were also available with an optional 3 spoke 'sport' steering wheel using a horn button. The dealer installed only Speed Control: The switch attached to the T/S handle.
1969/74 F100/250 2WD & F350 with M/S & P/S; 1975 F100/250 2WD & F350 with M/S only // 1969 Econoline from serial number D68,001; 1970/74 Econoline.
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- C7TZ-13318-B .. Cancelling Cam-Attaches to steering wheel.
1967/91 F100/350; 1975/91 Econoline; 1978/91 Bronco.
---------------------------------------------------------------- D3TZ-13341-A .. T/S Switch-Use with M/T .. ID tag looped over the wires marked: D3TA-13B302-AB
1973/77 F100/350; 1974/77 Bronco; 1975/77 Econoline except 1975/77 F100/350 & Econoline with Speed Control.
--------------------------------------------------------------------------------------------------------------------------------- D3TZ-13341-B .. T/S Switch-Use with A/T .. ID tag looped over the wires marked: D3TA-13B302-BB
Same applications as above.
--------------------------------
1973/77 F100/350: Horn relay located on the right fender apron close to the starter relay aka solenoid.
It looks like the cancelling tab is rubbing/touching that metal plate secured by the two dark colored Philips screws in the column. I wonder if that's the point of contact which is completing your horn relay primary circuit.
07-22-2017, 05:27 PM
