Tach upgrade

[Mike Rivers <beatlemikey@yahoo.com>]

Hi,

I upgraded my older non-funtional Jaeger tach to
Smiths internals recently.  It works good, however
when I switch on the turn signals and/or the brake
lights, the tach needle moves very irradically
(twitches).  I wired in a relay to it and no change. 
Do I need some kind of voltage stabilizer on this or
what?  Derf, what do you think?

Thanks,
Mike Rivers
1961 MG Midget 1275 Sebring