200tdi temp gauge problem

Hi everyone my first post on any forum ever I have a 1990 90 that spat its original td engine out recently.
So I've had a 1995 200tdi disco engine fitted, everything works really well except the temp gauge reads just below red though the engine temp is fine. I've been told that I need to change the thermostat housing for a 90/110 2.5 petrol engine version but thats v expensive an alternative is to use an "adapter nut part no ERC8973". Bought one of those but found that the original sender nut doesn't fit into the new one. What else do I need Help please

If you do a search this has been covered lots of times I believe the answer is to fit a different sender.

Yea, mine is esactly the same. My solution, is if its gone way into the red, feel the heater air tempriture with your hand. Very professional...

i had this problem with mine too!-
i have fitted a TIM gauge which comes with the sender unit and gives an actual temperature in numbers.
Very easy to fit and well worth it.
cost about 20 quid all in