Inverter Fans running continuously 1000 watt device.

[tytower]

I have a new inverter  24Volt to 240 Volt.
It was quiet during operations for a few weeks but now the fans come on and stay on whenever the unit is switched on.
Looking inside I see a 2 wire device attached to the heatsink but one only.
I have had it apart but did not take a pic of the insides .
I have one of the outside though .
Anyone with experience on this model or perhaps on generic brands on ebay who might help me work through some tests to find out how its controlled?
Is it likely to be microprocessor controlled nowadays or would the old transistors voltage change be used ?

[amyk]

I have had it apart but did not take a pic of the insides .
I have one of the outside though .

That's not very useful. More detailed pictures would help greatly.

You'll have to do some reverse-engineering of the circuit to figure out.

[tytower]

Got a few more . closeup is where the sensor attached to heatsink comes from board. Board says RT1 and there is 104 marked so 100K  thermistor I assume?

[tytower]

So not a lot of response?