[OhGeez]

You said you replaced the thermostat. It could be that the grounding wire isn't on tight enough or the wire is frayed so as to not make a good connection. Just a thought.

Also, just for the heck of it, have you re-checked you battery cables? Doesn't hurt to try.

 

[OhGeez]

Ditto on the main. If you need more info on that, click on the link in my sig.