Dome light stays on after head unit replacement

[Alistair]

I did a head unit replacement and now the dome lights come on when I start the engine and stay on until I turn them off, including if I turn the engine off and leave the vehicle.

Everything else is working great, including steering wheel controls, backup camera, remote start/lock/unlock via Fordpass, even digital climate controls.

Anyone know what might be the issue?

New equipment:
Sony XAV-4000 head unit
Maestro RR adapter

Original equipment:
4-inch SYNC unit (removed)
Stock radio (removed)
Manual climate controls (still in use)

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[airline tech]

I am not sure, but when you say turn them off , how are you turning them off?

FYI- you have (2) ways to control the upper dome (courtesy lights)
1. The rocker switch in the middle
A. Pushed Left - on
B. Pushed Right - off
C. Centered - Auto with the door open / key off/ on - and they auto time out

2. The individual light itself - is also a switch - press it to turn light off/ on

if that is not it , then the Sync circuit is keeping power on, it ties into the wake circuit.

 

[Alistair]

It turns on when the ignition starts, even if the rocker switch is pushed right/off. It doesn't come on before the engine is started, even with the key turned to the on position.

I usually turn it off by cycling the rocker switch.

I've tested once to see whether it times out when I lock the truck and it seems like it doesn't if it turned on with the ignition. If I turn it off after it turns on with the ignition then everything works normally (door turns fine light on, remote lock causes it to time out, etc).

 

[airline tech]

Being that this is an aftermarket HU, it may be in the wiring harness (adaptor) or in the HU controls.

Have you pressed the (Light) itself? - It works independently of the Rocker switch.
The light (itself) is also a switch.
The reason I highlight this is due to the fact that others have had this happen not realizing that the light itself is also a switch.

So, I wanted to point this out before you dig deep into troubleshooting the issue, for a simple (Oh-Crap)

I would hook up Forscan and see any codes, and also perform a BCM / FCIM / APIM self test.

The issue appears to be on the Bat-Saver circuit, on the OE HU it will power down the HU , IPC and Interior (Backlighting) plus Courtesy / Ambient when door is opened. (Times Out)
The new HU is keeping the Bat-Save feature from activating (Possibility)

After Time out:
Powers up when door is opened (IE Wake Circuit) - Partial Power Up until Ignition transitions to Accy or Start.

When key is released from start to run, the Dome Light (Courtesy) should power back off after (10-Seconds)

So, you have added into the circuit a new HU and also added a new wiring harness, and you had the FCIM disconnected. (The FCIM is the panel that has the manual PB switches on it for Climate / Radio controls.

So, somewhere in the circuit is not seeing the transition to power off the dome lights, it may be a locked code, and this is where a Reset of the modules above may get it working correctly.

Sorry, I can only go by what I can see in the OE that should be installed, anything aftermarket on the HU or Wiring harness is altering the intended power distribution.
I am curious if you were to power off the HU would the dome lights go off.

 

[Alistair]

Thanks for all the info!

Something I did when testing seems to have fixed it, which might be the light/rocker switch overlap. It's sort of weird that the dome light goes on/off for so many reasons but it still "remembers" the position of the one switch that you can't really see.

Regardless, it seems like it's working fine now. The dome light comes on briefly when I start the engine and then it goes off almost immediately.

Thank you again for your help!

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