You’re welcome. Hopefully I’ll remember to check for an update.

And I stand corrected on this - I’d completely forgotten this can be done in your situation as well.

Before setting up either the circuit breaker or the headlamp test, inspect the fuse block and wiring as previously stated - sometimes a good visual inspection is the best problem solver. 👍

In place of the circuit breaker, use jumper wires to connect a headlight bulb to the fuse terminals. In this case, I’d advise an older style headlamp, such as a 6054 or 6024, as they have a higher current draw than a 9006 and would provide adequate load for a direct short.

Just be careful with placement - the bulb can get VERY hot. If the heat seems too intense (unlikely but possible), wire a 2nd headlamp in series with the 1st.

Jumper wires about 2 feet long with mating spade terminals on each end (male for the fuse block, female for the headlamp) should give you adequate slack to place the bulb somewhere safe.

 

Question. I bought a headlamp bulb BP 9003-N from Napa Auto parts. Is that going to work or should I return it for a 6054 headlamp instead? Also is 10 gauge wire suitable? Thanks again!

 

If it were me, I’d get the 6054.

The reason I suggested the older headlamps is because 9000 series headlamps only draw 4-6 amps whereas the older ones can draw up to 15. With a direct short like this, the 9003 bulb may not be sufficient and either burn out right away or after a few minutes.

As resistance increases, current decreases, so the older headlamp should provide more than adequate load.

If you decide to use the 9003, wear safety glasses on the (possible but unlikely) chance the bulb bursts from the heat generated.

10 gauge wire should work perfectly, but you could always upgrade to 2/0 if it doesn’t hold up.

 

The 9003 bulb will work, there is only 12 volts being applied to the bulb and it's a 12 volt bulb. The shorted wire just provides a path to the negative battery post. The lower the resistance of the short, the brighter the bulb will shine.
The bulb will act as a current limiter, so 12 or 14 gauge wire will work.

 

I just tend to err on the side of caution - 9000 series bulbs get really hot under normal conditions, so there’s potential for an accident to occur, however unlikely it may be.

 

Update! I couldn't get the fuse box to separate under the hood. Didn't want to break anything. If anyone has a suggestion on getting that apart, that would be great. One question, does that area under the fuse box typically cause direct shorts? I made my test light using a 9000 series headlight bulb and installed it in the 40 amp fuse slot. Connected the battery ground and ae expected it lit up bright. Shook all the likely wiring suspects in the engine bay with no success. Tomorrow I am going to put the truck on Jack's to inspect more underneath. Currently the starter is removed. Looking at the schematic , I have looked at everything I can see with my eyes. What next? Thank you all who have replied with info! Very much appreciated!!

 

I finally separated the fuse box. No obvious damage under it. With the test light hooked to the fuse box, I have shaken the wiring harnesses and nothing has flickered. Question! After I disconnected the ignition harness underneath the dash, that would eliminate the ignition switch/ harness, correct? What ELSE does that 40 amp ignition fuse feed? My Haynes manual schematic is basically saying, starter relay, ignition switch. What am I overlooking?

 

Dont think that 98 Suburban has much to do with the 2021+ lineup, you're prob lookin for advice on those newer models. Can you tell me what happened when you replaced the blown fuse, or is your 2021 Suburban not even cranking?

 

My Suburban is a 98. It blows immediately when installing a new fuse. Key is OFF!

 

OK, still no luck finding the 40 amp Ignition short. But while checking over the fuses, I found the 10 amp Ign-E , 20 amp ECM-1 and the 20 amp ENG-1 fuses have no power to them in the run position. Could this be due to my 40 amp Ign A fuse removed? My schematics aren't the best. Thank you!