Coolant Temperature Gauge Sender

[Forrest]

The coolant temperature gauge on my 1997 940 has stopped working. I am 99% certain it is the sender at fault. I have removed the connector and tried shorting the two contacts and the gauge then swings fully to the right when the ignition is turned to position 2. In normal operation the needle doesn't move at all.

I have got a new sender and, for good measure, inlet manifold gasket on order from FRF Motors. However, I am quite keen to change the sender without having to pull the inlet manifold. It is the front, more accessible, of the two coolant sensors. My own skills are more electrical than mechanical.

Any tips on getting the old sensor out without wrecking anything or rounding off the brass hex nut? Are there any specialist sensor wrenches on the market that might improve my chance of success?