I think your IR gun would have limited effectiveness in this use and here is why:
IR thermometer guns look for infrared energy in a cone shaped area with the point of the cone being at the point of the gun. An expanding circle if you will. Any radiating surface within the circle will get used in the average. The laser has nothing to do with the function of the gun other than an aiming device. Dull flat surfaces work best.
You could try it but I think you would need to have the gun right next to the surface to minimize background temperature.
As others have said, learn how to diagnose with a volt meter.
