having some weird symptoms...hoping someone might be able to suggest diagnostic process...

brake lights quit working

tach starting acting erratically (not related to engine speed), bumping up and down, jumping around and dropping to zero/off, then occasionally coming back on and reading correctly

check engine, gen, water in fuel, and wait to start lights coming on and off

voltage output gauge dropping from 14 to 12... then back up again

A/C stopped blowing cold

engine performance seems normal

Any way all of these things are related????

Pretty much started all at once, except I believe the brake lights went out first

 

Tach signal is required to let the PCM know engine is running, so while tach is flaky you won't have AC, Cruise, or charging at the minimum.

Check the tach connector at the front of the engine, they can get oil in there and start acting funky. Clean the connector insides with contact cleaner, dry and see if that fixes it first.

 

front of my engine is totally covered with black oil sludge so that would make sense...
would it be safe to spray it all down with Simple Green and hit it with a pressure washer?

 

I'm not a big fan of pressure washing.......simple green and a garden hose?

I know guys who have done it but Murphy sits on my shoulder every time I get a bright idea....