I'm getting erratic temp readings on the gauge in my '82 300D. The problem is intermittant, but when fully warmed up the gauge will make instant transitions erratically between 85C and 100C.

I want to replace the temp gauge sender, so I bought one and I find there are two "sender looking things". One is in the head between GP 2 and 3, and the other is near the thermostat housing right next to the EGR valve. The unit in the head seems to control the gauge. What does the other one do? Coolant temp sensing for the climate control? Something else?

Art there any tricks to replacing the unit in the head? It came with an aluminum crush washer, but should I use anything on the brass threads before tightening it down?

Thanks,
Bob
'82 300D