Diagnosing older webasto

I am a municipal mechanic and am working on the road line paint truck. There is a older webasto unit which I believe is a Spheros DBW 350 model on it that in colder temperatures circulates and heats the paint to around 70 deg F. I have no experience on webasto units so just looking for some diagnosing tips and possible issues. The unit is turned on by a lighted on/off toggle and above it it is a digital temp display with a knob that can adjust the paint temp. The max setting seems to be around 75 deg F. When I turn the toggle on the fan in the unit comes on but the exhaust air never gets hot. After running for approx. 2min the digital display and switch go out.

I can see slight fuel movement in the inline filter but will be changing it when I get back to work next week.. Seeing the fuel movement tells me the pump is likely operating but plan on removing return line to see how much flow I have. My main question is with the ignition system is it possible to hear it attempting to ignite eg. clicking or snapping and can I remove the electronic ignition unit and visibly see if it is sparking? Is the ignitor common for carboning up and require cleaning? Is there any tests that can be done on the flame sensor or any way to bypass it temporarily to see if it allows unit to fire? Any info is appreciated.

 

Just thought of something. Since the webasto on this truck is designed to heat the paint to around 70degF if the ambient temp in the shop today was 80deg F as a example would the unit even fire? Maybe it is working fine and will have to be tested when the weather cools down?

 

thankyou I was googling webasto tech support earlier but did not have much luck. I believe at this point it wont fire due to fluid temp is to be at 70deg and today it was over that in shop. I will be removing the fluid temp sensor and putting it in cold water to see if it fires before I tear into it.