Thunderbird 900 Instrument Lights.

Oil pressure and high coolant temp. You don't want to see these.
I recommend that you replace the indicator bulbs with LEDs. I found it impossible to see the bulb light in bright sunlight, and it can be pretty awkward to use the clutch to feel if you found neutral.

 

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I wouldn't expect to see the light just because the fan has kicked in, I would expect to see it if the fan didn't kick in and the bike was overheating

 

Original filament bulbs. Neutral light under the oil pressure light is on.

 

After LED conversion.

 

Where did you get the bulbs from @Erling. As I'm a total dimwit with electronics, don't be afraid to go overboard with the information

 

As I had to order from abroad anyway, I got these wedge type LEDs from superbrightleds.com in the US. You'll probably be able to get them in the UK. Here's my order:
3X 74-GHP: Green
2X 74-RHP: Red
1X 74-BHP: Blue
5X 194-WW5: Warm White
The 194 LEDs were for the instruments, and I have so far not used them. The total order was 25 USD plus 18 USD shipping, but that was 2-3 years ago. A bit fiddly to replace the old ones, but absolutely doable.

 

Cheers Erling. Enjoy the rest of your weekend.

 

@Bikerman - let me know if you decide to order some of these from the colonial cousins- we might be able to share an order and split the shipping costs?

 

Will do, I'm going to try over here first.