LED lights and dash lamp

I have not actually used, whilst driving, my bus since I fitted LED main/dipped, sidelight and rear/stop lamp bulbs. They all work.
On the way home yesterday from a trip, in heavy rain, I switched on the lamps but don't get the dash light or the main beam (blue) lights coming on at all when activated. I am sure that last time I used the lights (with incandescent bulbs) the dash lights lit...
When I flash or select main beam I get the relay clicking okay and the dash bulb (I only checked the main beam bulb) is not burnt out.
The oil/gen lights work so assuming not an earthing issue,

Is there a compatibility issue with LED lights and the dash bulbs?

 

Dash lights are not an issue for LED headlamps.

It is an earthing issue for you.

The alternator light , indicators light and oil light are powered with a 12 v feed to the dash; the oil pressure switch provides the ground for the oil light, the alternator regulator the ground for the warning light and the indicator bulbs the ground for the indicator green light(s).

The dash illumination and the main beam indicator are both driven by 12 volts from elsewhere and the bulbs are connected to ground. Look for a loose brown wire behind the dash.

 

Thanks for that explanation Mike - I will explore...

 

Or turn up the dimmer knob maybe?

 

Good point - or the variable resistor has disintegrated. . But the main beam indicator light doesnt work apparently either. Which is not connected to the dimmer.

 

Thanks for the pointers chaps.
No loose earth and found now the bus was in the dark garage that there is a faint blue light with high beam. I also found there was no bulb/holder in the main light indicator slot and could not find a loose one!
I tried my blue lamp in this hole and the dash light was very bright - so don't know why so small/dim in its correct hole! Tried making a better contact, but...

What is this variable resistor people talk about? The light switch/knob does not rotate
Cheers

 

I'm guessing your model may be too early for this much sought after advanced feature (not).

 

The main beam lamp has a tiny square aperture behind the blue filter. If the bulb has blackened, it gets very dim.

If you take out the plastic aperture bit, the bright blue is disturbingly bright when you are straining to see with stock headlamps on main beam.