Issue with OEM LED bed lights and PryEU lights tied to cargo light switch

I installed the OEM LED bed lights last week and the install was successful. No issues noted. Today I installed the Amazon PryEU LED lights in the footwell and they all lighted up without any issue. Tested the front 2 after I installed and it lit up as expected. Then I tied in the rear two in series with the fronts and they all seem to be fine.

However, when I started the engine, the LED footwell lights started flickering along with a sound like a relay rapidly latching on and off. I didn't think there was a relay in the cargo lights circuit since there's not much load. I shut off the engine and everything went back to normal. So the lights work fine when the engine is not running but flash rapidly when the engine is running.

At this point, I can only assume that tying both the OEM LED bed lights and the PryEU LED lights might just be a little too much for the cargolight circuit. FWIW, I have not yet changed out the brake and cargo light bulbs on the back of the cab to LED and am not sure if that will cause this problem.

I am trying to find out if the interior cab light is on a separate circuit since its controlled by a different switch and if it is, what would be the correct wires to tap to. Tried to search for a wire diagram that has both the cargo light and interior light circuits but am coming up empty.

Any ideas?

This is on my 2018 SR5 DC.

 

I would consider using a relay with the cargo light wire as the trigger. that way the load on the cargo circuit is minimized as the relay will handle the more significant current. I bet that will clean it up for you.

First I might check the connections and verify there isn't something contributing there too...

 

Wanted to provide an update. I removed the cargo light bulbs(on cab rear) to see if it would make a difference but it did not. Issue is still there when the engine is running. Since I am still unable to find the wiring diagram for the interior cab light switch, I tied it to the small footwell light above the parking brake pedal for the time being. Was hoping to tie it into the interior cab light switch so that I can turn it off/on with the rest of the interior lights.

 

After reading this last week I bought those lights and wired in the front ones basically into the cargo switch wiring and they have worked perfectly. I didn't do the rears because I was a little short on time and didn't quite figure out how to mount them (no hard surface to stick them to). Where did you stick the rear ones under the front seats? the small drivers side footwell light is controlled by the cargo light switch. I'd also like to figure out where to tap the dome light switch for a different project too.

 

I bought outer corner molding from home depot and cut it down to size to fit between the plastic flanges under the seat. it is held in by the seat cover elastic bands and compressed by the plastic flanges. Have it angled so that the LEDs are 45 deg throwing the most light on the floor. I'll get some pictures later tonight.

For power, I tapped off the little footwell light bulb just above the parking brake pedal. They're all wired in series and I used bullet connectors to connect each rear light and in the passenger door sill cover to get to the front.

 

I have the OEM LED bed lights so 6W each and the LED strips are rated at 1.5W each so 4 strips would be 6W. Total draw would be 18W would be 1.5A added to the cargo light circuit. Whats weird with this situation is that when the engine is not running, the lights are all lit perfectly without any issues. It is when the engine is running that i get this pulsing issue. I've looked at various wire diagrams that I've pulled off the internet but have not been able to find any relays that power the cargo light circuit so I don't know what is causing this. The fuse should have blown if I had overloaded the circuit but it has not which leads me to think that it is something else that is causing this when the engine is running. I've since tapped the footwell light bulb to power the LED strips and issue has gone away so I have not looked into this any further.

 

maybe that's the issue, wiring them in series vs parallel. Why not wire them in parallel?