I was upgrading my radio from an old pioneer so just plug and play and now there is no backlight for the speedometer and the gauges. The trip computer is working fine and its bulbs are on.

Where should I start looking for the solution?

 

Gauges are only backlit when headlights are on.
there is no reason at all i can think as to why a radio install would affect this.
unless somehow there is a short caused when you did the radio install. But if this were the case i would say the illumination on the radio and the ac controls would also not work

 

AC controls, the clock and all the warning lights are fine. Its just the gauges backlight that is not turning on. I might have touched a ground or shorted something, but just the gauges backlight are not on a separate fuse.

What is this braided ground strap behind the radio for?

 

Is it possible that all your globes are blown? Unlikely but hey possible i suppose anything is not sure exactly what that cable ids. But if it is an earth strap it should be earthed.

do your gauges themselves work?

 

Everything works except the backlight. I doubt dozens of bulbs burned out at the same time while i was working on the radio.

Another clue is that when I turn on the headlights the trip computer backlight turns off as well, it's not dimming like it should. So maybe it's the dimmer? Where is that located?

 

I doubt all bulbs burnt out at the same time too.
(gaugecluster is 8 backlights, +2 for odo)

but i also can’t see how some backlights work and others do not as they are controlled by the same circuit.
if something like the dimmer was dead all the dimmer controlled lighting would be affected. The dimmer is on the sides of the steering column
it has to be something with the cluster or the wiring to the cluster.

i have never noticed the odometer display dim at all.
i have always thought it was always illuminated the same amount.

 

All the lights (clock, trip computer, and ac i thing) dim when you turn on the headlights.

 

Check the red/orange wire coming from the dimmer to the instrument cluster

 

Info for you. (TSBs that nobody reads)

 

mmm.
ac is only lit when headlights are on. And dimmer controlled same as instrument cluster.
never noticed the trip computer and clock dim when headlights are on. They should be always lit non-dimmer controlled.
is this potentially a ground issue?

 

Other than wiring malfunctions, Motorcarman's TSBs should cover it. The heavy ground strap in the console is for the radio head unit.

You will want to connect that ground strap to the radio and while you're in there, check the other nearby grounds and especially any splices that were made (by others) to connect the aftermarket radio wires.

Odo, clock and A/C display dim with the other backlights. They go brighter when the bypass is engaged with the little knob.

 

depends tho.
on aftermarket headunits there is nowhere to connect the factory heavy ground strap, thus making it obsolete.
they use only the standard ground wire.

 

So the dimmer isn't really doing anything , only the bypass is working. Here is a video to better explain it. I'm still getting no light for the instruments.

 

Similar problem / system here

Backlighting on dash switching off even with the main beam on - Jaguar Forums - Jaguar Enthusiasts Forum

 

The original factory Jaguar / Alpine installation

This is the non premium option without the power amplifier in the trunk

 

Fixed it, it was some random fuse under the rear seat

 

clearly not random. lol