3.8 Headlamp Jewel Light Colour

[Philk]

On my long list of things to research (and Covid-19 provides the ideal opportunity) is the colour of the Main Beam warning light in the speedometer on 3.8 cars and when this changed from red to blue.

On my June 64 3.8 OTS, the jewel appears blue when looking at it in daylight but when you put main beam on at night, it lights up red. I've just been looking at a couple of different Operating Manuals I have here (a modern version from Brooklands books (122/7) and my original version (122/5)). Interestingly, the wording of the two books (page 3 on each) is different as per the photograph below:



The wording on the left is from the reproduction book and the version on the right is from my original 122/5. As you can see, the reproduction book refers to a red warning light whereas the one period to my car is silent on the colour of the warning light. I am not sure what version the Brooklands book was aiming to reproduce but it does not refer to outside bonnet locks so must be 122/2 or later.

Does anyone know the cut-off point when the red main beam warning light became blue. Was this later in the life of the 3.8, early in 4.2s or at a later point completely? Did it vary from country to country?

[chrisfell]

1967 ( Feb) S1 2+2 has a red tell tale for the main beam.

[mtnjag]

My 62 OTS made in Nov 61 is red when lit.

[rswaffie]

My Nov 63 FHC has a blue jewel, lights red.

[Philk]

Great LED lighting. Is your car +ve earth or -ve?

[rswaffie]

Positive.

[Philk]

Positive.

That's interesting.... were they specific LEDs you had to purchase - I had understood from other posts on this topic that the vast majority are wired for Negative earth.

[rswaffie]

From memory, the supplier listed +ve and -ve versions of all the dash, sidelight, indicator bulbs. So I’m assuming there is a requirement to match the bulb to the car’s polarity. All bulbs, apart from the headlamps (which are H4 with the relay upgrade) are LED. Tell a lie, I did have the ignition warning lamp an LED but the associated resistor kit that came with it caused significant parasitic drain so I reverted to standard bulb for that. I also replaced the map lamp for an LED strip - much more effective.