Ls400 Tach Problem

[vltjr]

Recently my '91 LS400 has been experiencing a tach problem that is slightly different than those that I've read about in these forums. On start-up the needle jumps to 500rpm and just stays there regardless of what the actual engine speed is. Before this problem occurred, I was having some intermittent problems with the tach just sitting at zero for a short time after starting (twenty seconds or less). Any ideas?

Thanks.

[Lexozz]

Recently my '91 LS400 has been experiencing a tach problem that is slightly different than those that I've read about in these forums. On start-up the needle jumps to 500rpm and just stays there regardless of what the actual engine speed is. Before this problem occurred, I was having some intermittent problems with the tach just sitting at zero for a short time after starting (twenty seconds or less). Any ideas?

Thanks.

I could only assume that the spindle or contacts are either worn or corroded. I have a similar problem when starting the engine, the tach sticks at zero until I hit the dash then it wakes up.