I replaced the bulbs behind the HVAC controls. On each of the three dials, the selector light comes on when you choose (ie switch from face air to legs air).

The illumination at night of all three dials does not work, they do not have a back light that lights each single HVAC option.

QUESTION:
Does one single bulb cover the illumination of all the options or does each dial have illumination provided by their individual dial?

Probable Solutions:
1. Something is wring with the wiring for the illumination?
2. A single bulb covers all three and I inserted with wrong polarity?

Trying to figure out how to diagnose the night illumination on these HVAC controls.

Thanks.