Instrument Panel bulbs not working

Hi Guys,
Can anyone offer any advice?
I had to remove the under dash tray on the drivers side which exposed some wiring.
After refitting I noticed that  the instrument dials illumination stopped working.
I checked the fuses and a 10amp had blown so I changed it but still no illumination in the dash.

All the LEDs still work. What have I done?

I believe there are 3 bulbs behind the dials but they can’t all blow at once, or can they?
The ignition or lights weren’t on when I managed to blow that fuse. I have rechecked all the fuses and they're all still good.

Are there other things I can check before I have to take out the instrument panel to change the bulbs?

Please help.

Check your main feed in to the cluster (clocks), ir is a Gray/blue wire usually, as well as the Ground wire into the cluster(brown) pin 2.  

If you have no voltage on that gray/blue wire then you won't have any bulbs.

LED Bulbs are Polarity aware, and if these are new to the cluster then you may have them installed with the wrong polarity,  removing the bulbs and turning them 180 degrees then re-installing them will usually resolve the issue.

Now the Grey/Blue wire on earlier Cabriolets was unfused to a point and has been known to burn a few things up, So I would advise you to check the gray/blue wire to validate that if it melted and fused itself or burned the insulation of of other wires.  It goes to evey, lamp in the dash.  

Placing the Year of your Ride and Model  in the first few lines of text goes a long way in us helping you.

Thanks Briano and apologies, It's an 83 4 door carb manual GX. The instrument cluster is a speedo and rev counter.

I have owned the car since 2011 and the instrument cluster has never been removed during this time and the dash lights have always worked. That is until I removed and refitted the the driver side lower dash tray.

I understand what you say about the blue/grey wire but as I say the cluster is still attached and I want to know if anything else could affect just the dash bulbs, before I start pulling everything apart.

The LEDs and everything else works in the cluster just not the illumination.

Could it be the dimmer dial on the headlight switch?

Thanks again

In my experience, the first time I removed my cluster to replace one bulb in the clock, the other two bit the dust, and didn't notice it until I have it all re-installed… (so remove it again.

So I got in the habit to replace them every 5-6 years if I was inside the Dash for any reason.

Thanks again Briano, but could the headlight switch have anything to do with the dash illumination not working?

I removed the headlight switch and noticed that the little copper contact that slides across the rheostat coil to adjust the brightness of the dash illumination was not making good contact. This had always been a bit iffy, so I cleaned the coil with alcohol and bent the copper contact down a bit so that it made better contact.

However, the switch started smoking when I switched it on!!

What have I done?

Cleaning and improving the contact did not fix the dash illumination either.

The grey/blue wire you mentioned is good as are all the others with no wear or damage at the switch end.
I have not yet removed the instrument billet.

Was a faulty headlight switch the problem in the first place or is this not related to the dash illumination?

With a "normal" set up, led's will either be full on or off when you turn the Dimmer there is usually no dimming it's either full on or off.

A short answer is yes.  That is if you have observed the Proper polarity of the leds to the dash. If they don't work, then turn them around in the socket (180).

Do they now work?  

Thanks for coming back Briano,

The instrument illumination has always worked ever since I got the car in 2011, so the bulbs were and are still fitted correctly as I have never removed the cluster and tampered with them. The illumination just suddenly stopped working a couple of weeks ago.

I've ordered a new headlight switch which should arrive in a few days. I'll let you know if this fixes the instrument illumination.