help with reflow station

the other day my yihua 8508D heat gun stopped working. the display comes on,but no heat or air flow. I have verified that the air pump works outside of the unit. there is some info on the unit here:



https://www.alibaba.com/product-gs/216305021/YIHUA_8508D_diaphragm_pump_Hot_Air.html



it says that the heating element is supposed to be 90 ohms, but im measuring 20 ohms. I removed the connecter where the heating element connects to the circuit board. I measure 120v across the two connectors,but when I reconnect the heating element I only measure a few volts AC.



im thinking that there may be more than one issue. does anyone have any advice or pointers for me? also, anyone know where I can get a schematic for it? thanks!

the heating element is supposed to be 90 ohms, but im measuring 20 ohms.

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Is that with the element disconnected from everything? If so, the low resistance may have caused excessive current flow and blown a fuse or burnt out any switching/control device.

Edit: If the blue cube next to the air pump connector is a relay, check the continuity of its coil.
The adjacent BT136 transistor is also a possible failure candidate.