The thermostats are in (dare I say it?) series and are actually controlling only heater #2. Heater #1 is controlled only by the breaker or fuse(s) for that circuit. Assuming that all the illustrated connections are in accessible boxes or enclosures, the fix is easy. Connect the black for each thermostat directly to the black from the supply. Disconnect the black supply from any other connections. Leave the remaining connections as they are.
The fact that heater #1 supplies only low levels of heat suggests that these may be 240 volt heaters supplied at 120 volts. Not dangerous, but output is only 1/4 of the labeled wattage.

This post was edited by bus_driver on Tue, Apr 9, 13 at 6:44

Round II

Well ... got heater #1 / thermostat working fine (black from thermo connected to hot black), but for why I don't know the black wire coming from heater #2 / thermostat is hot -- meaning, if I connect it (and heater #1 black) to incoming hot, the breaker Does Not Like That!

Do appreciate any interpretation of status you can give.

Thanks.

I have no ability to make or post sketches. Can you post a sketch of your revised connections?

You also need to know about the thermostats. Many line voltage thermostats like these will operate both sides of a 240 line if you need them to.

Back again. Trying to increase my knowledge base on this business .... finally got around to using the voltage meter; results are attached. Now I REALLY don't understand what's going on.

Also, when I have heater #1 connected separately, it remains on low heat and the thermostat has no effect on it .... ?!

Thanks again for your considerations. Much appreciated.

This is beginning to look like a troll.
Electricity poses too much potential danger to joke around about it.

Don't appreciate being called a troll. Further, no one on my end is "joking around" about anything. I think I'll talk with someone else. Thank you.

I am not sure what the problem is here. The black feed wire should connect to the two black wires, one to each thermostat. The white feed wire should connect to the two white wires, one to each heater. That's it.