I switched all my dash lights to LED last year.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
Red=alt, Blue=hi-beam,Amber=Fan,Green=Turn
I used the 24vdc version as I don't like blindingly bright caution lights. These can easily be seen during the daytime as well.
Had to add a Resistor as the LED did not have enough resistance to trip the alternator on and also turn off the light.
https://www.amazon.com/s?k=Twidec%2F...f=nb_sb_noss_2
Back to the OP original question. The alternator may have set too long causing the original problem.
https://www.engineersedge.com/motors...d_flashing.htm