According to one of our customer's Boeing 737NG Maintenance Manuals, the Window Heat Overheat Test should make the green Window Heat "ON" lights go out. The test simulates an overheat and the protection circuits trip off the window heat, causing the green ON lights to go off, the amber Master CAUTION to illuminate and the ANTI-ICE annunciator lights to come on. After running the test, you must cycle the window heat switches OFF then back ON again to get the green ON lights to come back on. This doesn't seem to be happening in PMDG's NG... or, at least, in my copy of it.BTW, the green ON lights indicate that there is heater current flowing to the respective window. The normal target temperature is 110degF (43degC). If the temperature exceeds 145DegF(62 C), current is cut to the window and the ON lights extinguish. I haven't yet tried to simulate an OAT of 62C to see if this is the case :-) (but it would be a nice Easter Egg for 737NG engineers if it did).Cheers.Ian.

I also meant to mention that toggling the Overheat Test switch for 1 second should leave the OVERHEAT lights illuminated.... and I should have mentioned that the green ON lights should extinguish _within 70 seconds_ (to be a successful test).Cheers.Ian.

I font remember the 70sec thing, but the onlight should go out, havent tried it in the sim yet.DennisLicensed on the B737NG and the Airbus 319-321 as a technician (B1 and B2)