Upfitter switch power problem

If I have power at my Aux3 switch (switch light works) but no power at the AUX3 wire behind the glovebox ( I do have power at the other 3 wires) .. I assume the fuse is fine since I have power to the switch light.

I don't have a wiring schematic so Im not sure of the inline order. Does the wire behind the glovebox come directly from the switch, or from the fuse/relay? Im not sure what order to look to find the cause of the dead wire.

I am not an electrician but I can manage a volt meter

Thanks for any help … I wired my 10 Duallys to AUX1 and my 20in to AUX2 … I can put the rear Duallys on AUX4 but I would like to get the AUX3 wire hot.

Check the fuse. That wire doesn't come directly from the switch.

Rookie said:

Check the fuse. That wire doesn't come directly from the switch.

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Fuse in 44 position is good

So where do the hot wires behind the glove box come from exactly? Not sure where to start tracing back to to figure out where the power interruption is.

Could it be a bad relay?

PCDan said:

Fuse in 44 position is good

So where do the hot wires behind the glove box come from exactly? Not sure where to start tracing back to to figure out where the power interruption is.

Could it be a bad relay?

Click to expand...

Possible. Take a relay from something that works and put it in to check. Also, not to insult your intelligence but make sure you're checking the right wire.

Rookie said:

Possible. Take a relay from something that works and put it in to check. Also, not to insult your intelligence but make sure you're checking the right wire.

Click to expand...

Yeah I was thinking of swapping out a relay.

As far as checking the right wire, I have checked each AUX hot wire behind the glove box for power, 3 have power 1 does not. AUX3 wire is dead.

Do the hot AUX hot wires come directly from the fuse/relay ?

I only ask because it's easy to mix up the pass through wires with the supply wires.

I'm not sure on the specifications on the wire routing.

The manual shows which relay is for what on the aux switches but the last time I checked them I found that the manual wasn't accurate.

Rookie said:

I only ask because it's easy to mix up the pass through wires with the supply wires.

I'm not sure on the specifications on the wire routing.

The manual shows which relay is for what on the aux switches but the last time I checked them I found that the manual wasn't accurate.

Click to expand...

No problem asking, I appreciate the help.

Pretty sure I have the wires right. I have lights on AUX1 (yellow-red), AUX2 (Green/blu - Green) working fine. The AUX 3 hot (purple/green connected to Blue) is dead (checked at the connection behind the glovebox), and the AUX4 (small brown - small purple), which are both really small wires are hot.

I found a diagram in here that shows AUX 3 fuse as #44, and AUX3 relay as #62 in the front fuse box. Im not sure if this is accurate as that was in 2010 and I also saw a post that said the upfitter switch relays were the relays in the box in the engine compartment nearest the driver firewall? I switched out the #62 relay with the #85 relay and still dead.

PCDan said:

No problem asking, I appreciate the help.

Pretty sure I have the wires right. I have lights on AUX1 (yellow-red), AUX2 (Green/blu - Green) working fine. The AUX 3 hot (purple/green connected to Blue) is dead (checked at the connection behind the glovebox), and the AUX4 (small brown - small purple), which are both really small wires are hot.

I found a diagram in here that shows AUX 3 fuse as #44, and AUX3 relay as #62 in the front fuse box. Im not sure if this is accurate as that was in 2010 and I also saw a post that said the upfitter switch relays were the relays in the box in the engine compartment nearest the driver firewall? I switched out the #62 relay with the #85 relay and still dead.

Click to expand...

My manual lists the upfitter relays in the compartment nearest the driver's side firewall like you stated. They're not labeled and the diagram doesn't coincide with their respective uses. I pulled the one it said for aux 2 and aux 1 went down.

Rookie said:

My manual lists the upfitter relays in the compartment nearest the driver's side firewall like you stated. They're not labeled and the diagram doesn't coincide with their respective uses. I pulled the one it said for aux 2 and aux 1 went down.

Click to expand...

I swapped all of the relays in the drivers side relay box with the relay for AUX 1 and all relays work fine. (there are 5, 4 for switches 1 for front camera)

If 12V power goes to the fuse block, then to the relay, and then splits from the relay to the supply wires (behind glovebox) and to the switches … the problem must be at the connection leaving the relay or between the fuse and the relay .. unless there is something between the relay and the supply wire? Im pretty much screwed lol


12V - fuse - relay -> supply wires and switches ----- maybe?

Each relay uses four wires; two for the accessory power and two for the trigger circuit. The exact relay terminal numbers may be different between the image above and your truck, but the principle is the same.

Terminal 87 would go to your accessory/lights.
Terminal 86 would be switched (trigger) from the upfitter switch.
Terminal 30 is supply to the relay that passes through to the accessory when the upfitter/trigger is switched.
Terminal 85 is the ground side of the trigger/upfitter.

It sounds like you have a bad relay or a bad 'terminal 87' circuit in your truck.