Did you replace the dash indicator too? The dash indicator is across the hot leads in the circuit and it might be the culprit due to the impedence difference. When I put a LED in my dash I learned that I had to use two, one polarized each direction. I think there is a proper LED available for that function now.

A positive attitude may not solve all your problems, but it will annoy enough people to make it worth the effort. Herm Albright (1876 - 1944)