Engine won’t shut off

If the upfitters are that delicate they only meant to trigger a relay, 20ga wire should be kept to a max of 5A, or about 60w per upfitter. Rigid claims their DSS in driving pattern consumes 4.07A @14.4v, which is [email protected] 12v. Meaning if your running more than a single set of pods off of your upfitters you need to invest in a relay. There are pre-wired kits available that take about 20 minutes to install if your meticulous with the zip ties.

I don't understand why ford put 20a fuses behind 20ga wire.

 

To clarify, here are the Aux Fuse ratings and wire gauges:

Aux 1 - 15 A Fuse - 16 gauge wire
Aux 2 - 15 A Fuse - 16 gauge wire
Aux 3 - 10A Fuse - 20 gauge wire
Aux 4 - 10A Fuse - 20 gauge wire
Aux 5 - 5A Fuse - 22 gauge wire
Aux 6 - 5A Fuse - 22 gauge wire

As a general rule in automotive electrical, the continuous load of a circuit should not exceed 80% of the fuse rating. If the lighting was drawing 4.89A through a 5A fuse, it's right at the maximum. Any high resistance at the connection between the factory aux circuit and aftermarket circuit could generate enough heat to melt the wire.

 

High resistance or circuit overload. It is important to remember that a 5A fuse will not open at exactly 5A; if the lights were drawing 5A or slightly more 5A for 2 hours, combined with any heat generated from resistance within the connections, it can create enough heat to melt the wire. I would be curious to see what OP's light setup draws when connected to a 12V source for 2 hours; that may help with determining what lead to the failure. This test could be accomplished relatively easily by connecting the Rigid light's 12GA wire to the vehicle's battery through a fused connection and installing an ammeter in series to measure current.

 

The only thing that can melt a circuit is high current or high resistance caused by the aftermarket lighting. Neither is warrantable. If Ford, or any other OEM called back that harness, they'd be charging the dealer back for the claim.

Ford uses the appropriate sized wire per industry standards for the current rating of the fuse. See my earlier post with the aux fuse and wire specs.

 

@Dan Larsen you said you have 3 sets of lights. how were they wired?

 

cant tell you how many times i have said this.

 

I used this rationale since its the same in household wiring.

 

So to clarify, you are saying the fuse is sized for the maximum current the wire can handle? The load on the circuit should therefore not exceed 80% of the wires maximum allowable load.

I typically put a fuse on a line (as in on my RTMR) that is just big enough to handle the load.

So for the upfitters, you are saying stay below 80% of their rating?

 

10A use 8A max.

 

I’m with you on that.

But am just verifying that the 10 amps that is being referred to is the maximum for the line.

Meaning a hypothetical line can handle 20 amps but is fused for 10, then you could run a 9.7 amp item off of it no problem.

but if it is safe for 20 amps and fused for 20 amps, you would want to honor the 80% for it.