Had a winter maintenance call for a car wash with Cambridge MAUs.
below is the flame sensor, notice how its worn down to a nub. Amazingly it was still able to read flame. told mgr need to replace sensor, didnt wanna do it.
The second is the amount of clearance i had at the blower door.
Third is looking in at the blower, couldnt get a good photo of how loose the belts were.

3 months later get the call for no heat. new sensor vs old sensor