Gtd80y

Yes it was a brand new genuine part from TPS, fitted at a VW specialist. The car takes 11 mins to hit 90c driving at 30mph without heaters. As soon as heaters go on it will start dropping. The DSG thermostat was a genuine part aswell from TPS

No air lock, tried back flushing heater matrix aswell and flow was good. Needle only drops when heaters go on otherwise stays solid 90

Hi all I’m having issue where my temp needle drops with heaters on. I have replaced main thermostat, dsg stat, 2 x coolant sensors, water pump, flushed matrix, bled system. OEM parts fitted . Any ideas what else it could be? Tdi 170 CFGB

Hi mate, did you ever fix this issue? I’m having same problem

Hoping someone can help with this as I’m out of ideas. Coolant temp needle drops when I turn heating on Main thermostat replaced Dsg inline thermostat replaced All coolant temp sensors changed Fresh coolant New waterpump 0 fault codes , scanned using vcds All genuine parts Heaters are HOT when on Hi, but if I turn it down 1 notch it is cooler CFGB Any ideas? Thanks