Overheating Problem?
Guessing from the picture (you can see the resistor values).

Resistors:


1001 - 1K
1801 - 1.8K
2701 - 2.7K
2202 - 22K


The lowest value resistor is 1KΩ.

Ohm's law:  

\$V = I*R\$ or \$\frac{V}{R}=I\$  

\$\frac{12V }{ 1000\Omega }= 12ma\$

Now, Solve for power

\$Volts * Amps = Power\$
\$12V * 0.012A = 0.144W\$
As such, the lowest-value resistor, connected directly across the leads will only produce 0.144W of heat, or 144 mW.

The other resistors will be less.

You will have to decide what "too hot" is. It shouldn't produce that much heat, though.



Of course, this is just for the resistors. Your device has a diode and a transistor on it. We can't estimate the power they are dissipating without a schematic, or some sort of documentation.

What is that thing, anyways?