05 fog lights won't turn on

jrex2506 · Mar 7, 2020

Fuse #43 is good. Low high beams work. The fog light indicator doesn't light up when pulled out. Bulbs are good. Any ideas?

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6.0 Tech · Mar 7, 2020

jrex2506 said:
Fuse #43 is good. Low high beams work. The fog light indicator doesn't light up when pulled out. Bulbs are good. Any ideas?

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Is the key on when checking?

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jrex2506 · Mar 7, 2020

Yes, it is. lol I double checked that. I had some other lights tied into them. So I thought it just shorted out and blew a fuse. Is there another fuse I need to check?

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bismic · Mar 7, 2020

Check the grounds.

jrex2506 · Mar 7, 2020

Do the fog lights have their own grounds?

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TooManyToys · Mar 9, 2020

The fog light circuit got a lot of changes during the years, and it's not the same as laid out in the 2003 service diagrams as it is on my 2003 truck. I played with this circuit on both my '01 and '03 trucks so I could have the fog lights on with highs.

One of the things confounding you may be that Ford utilizes an embedded relay for the fog light control over some years, embedded into the CJB that is not replaceable, it is soldered in. Without having the specific diagram for your production date would be hard to do.

bismic · Mar 9, 2020

jrex2506 said:
Do the fog lights have their own grounds?

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The ground is the G100 (black wire). Firewall drivers side IIRC.

Power is supplied through the CJB relay connector C270h (TN/OG wire).

You can pull the fog lamp connectors C152 and C162 and turn the fog lamp switch on ..... see if there is voltage between the power wire (TN/OG) and the battery negative terminal.

PSD POWER007 · Mar 14, 2020

This is an interesting follow for me. My 05 Excursion, the fogs will work most of the time but have times where they just won’t come on. I’ve been wondering if it’s the switch or relay or something.

bismic · Mar 14, 2020

Sounds more like a relay issue, but please post the solution when you find it!

PSD POWER007 · Mar 14, 2020

Know where the relay is?

bismic · Mar 15, 2020

That relay, along with a few others, is built into the CJB or Central Junction Box (fuse panel under the dash on driver's side):
Fog Lamp Relay
Fuel Pump Relay
Horn Relay
Trailer Tow Parking Lamp Relay
Heated Mirror Relay

It is considered a non-serviceable item and, if bad, Ford will recommend replacing the entire CJB.

PSD POWER007 · Mar 15, 2020

Oh great....

bismic · Mar 15, 2020

The best thing to do if you STRONGLY suspect the relay is to just cut the wires to/from that particular relay and add one to the wiring external to the CJB. If I have some time, I will try to look up the connector number and wire color.