The HVAC contactor chattering and hang ups part 3

A demonstration of the problems that can cause HVAC contactor chattering and hangups. Low voltage and armature wear are covered.
If you are a homeowner looking to repair your own appliance, understand that the voltages can be lethal, the fuels are highly flammable and high pressures are used. Know your limits.

[grayfurnaceman]

Weak transformer would have low voltage when read with the contactor energized. Same with incorrect tap. Stat wire too small would also show up as low voltage. Absolutely a loose connection could cause chattering. I would think the contactor would have to be fairly massively oversized to cause chattering. Thanks for the thoughts, more to look for.
GFM

[samuelm]

Mine chatters when the ac is reaching the temp and ready to shut down. Is that a thermostat issue?