Custom desoldering station using Weller DSX 80

[Tebbit]

So i bought this brand new old stock Weller DSX 80 desoldering gun on ebay for 200€. And i'm stuck on what kind of thermocuple weller is using. I can only read 22 Ohms at 23°C,  if i heat the tip with a heat gun the resistance changes from 22 ohms to 35 ohms. From my guess its some kind of PT, but not PT100. 

I wanted to use Shinko regulator with SSR and 24V transfomer. 

If anyone has any ideas for what they are using much obliged.