All four of my fender marker lights on my 1993 F350 quit working at the same time.

All the fuses appear good even though I could not determine what fuse was for the fender lights. I replaced the relay that appears to be for the fender lights from what the owners manual claims.

All the other lights work fine including the cab top lights and trailer lights.

I looked for a thread about the fender lights but could not find one.

Help please!

 

I'd replace the fuse even if it looks good but that's not a permanent fix. You most likely have a short or a piece of bare wire to the running lights arching on metal. Sometimes a wire can rub on the frame, body, crossmembers, etc causing this.

 

A quick way to test fuses using only a test light:

Look at your power panel, and pick a fuse to start with. At the top of it on either side of the amperage rating you'll see the backside of the metal terminal prongs. Leave the fuse installed in the panel, and ground your test light wire. Now touch the test light probe to each metal prong on top of the fuse. Read results like this:

- No light when testing either terminal = Circuit open upstream of fuse
- Lights when testing one terminal, but not the other = Fuse is blown
- Lights when testing either terminal = Fuse is OK, may have open circuit downstream.

Do this for all the fuses. You can use a meter instead of a light, but then you have to look at the display each time which can be a pain sometimes.

 

It would be fuse "D" under the hood.





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I checked fuse "D" under the hood again. Power to both sides. On a side note I would like to thank the person that came up with the idea of test holes on top of the fuses. Pure genius!

I also pulled two of the lights on the fenders just to be sure there was no power there. There was not.

Next I'll try jumping the relay when I get home from work. I suppose a hot to the terminal that is not hot, hot when switched with the headlight switch, or a ground should send power back to the lights. Just to confirm the relay is #2 in the small relay box to the rear of the fuse box, correct?

 

REALLY simple test.

Do your tail lights work?

YES? then the PLUG under the bed has come loose or rotted off

NO? The look at the main plug where the bed plugs in under the bumper

 

This would work if the fender lights were not on a different circuit than the taillights. Unfortunately they are.

 

Not from the factory they are not.

The fender lights plug into the bed harness. The bed harness plugs into the chassis harness

 

Not sure what truck you are talking about but from at least from 1988 - 1996 the Factory F-series trucks are like the wiring diagram that I posted above.

As duphofff said above:
"This would work if the fender lights were not on a different circuit than the taillights. Unfortunately they are."

 

Any 87-97 F350 dually pickup

The dually fender light harness PLUGS INTO the taillight harness. The taillight harness on a dually has 3 extra plugs on it (one per side for the dually fenders and one in the middle for the ICC light bar)

I'll get pics if i feel energetic. In the mean time the OP can look under his truck and see the 3 plugs I am talking about

 

Then you are saying all of the wiring diagrams that Ford has published on this from at least 1988 to 1996 are wrong and the relay is just for looks.

 

I never said that.



Brad is correct it is in the same harness. But the fender lights and ICC light bar are in a different circuit within that harness. Harness - Circuit = Apples - Oranges.

Between mowing and other yard work I have fiddled with the truck. There is power at #87 at the relay and when I pull the #4 fuse that power disappears. That being said there is power at the relay.

When I turn the headlight switch on none of the other lugs are hot. I believe it should be #86.

When I jumper from #30, which I believe should go to the lights they do not light up.

Now that I think about it I will power one of the light wires from the battery and see if it heats up one of the terminals at the relay.

I will report back after more yard work.

Bill-
Do you know if the power to the relay from the switch comes directly off the switch?

 

What you quoted I was saying to Brad and not you.
From what you say confirms this.

The power to the coil of the relay comes from the headlight switch through connector C202.
The contact on the headlight switch is powered by fuse #4.

 

Ok. now this is driving me nuts!!

I ran a wire from the positive side of the battery back to one of the fender lights. I tried both terminals with a test light. No ground at the fender light terminals.

I then used the same wire from the the positive side of the battery and tied it to to one of the red wires at the fender lights. This energized all the red wires at the fender lights but I had to use a ground other than the one at the light to get the test light to light up.

This leads me to believe I have a bad connection where the harness for the fender & ICC lights connects to the back side of the relay. Remember I ran a hot wire directly to the #30 terminal at the relay and it did not energize any of the fender lights. No ground and no positive leads me to believe both are disconnected somewhere.

David

 

Putting power on #30 with the relay out will not light the lights. Pin #30 should be hot from fuse "D".


It sounds like G401 does not have a good ground:

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