Have I wired this up wrong?

I can’t get the temperature gauge to work properly on my Land Rover. My Series IIA has the 2.5l petrol defender engine. On the block there are 3 sensor terminals: 1. On the filter casing there’s a terminal, connected to the oil pressure warning light, which works. 2. On the n/s/f of the block, at the top, just behind the thermostat housing, is a terminal in a flat topped sensor, held in by 3 bolts, which is connected to the temperature gauge. When the engine is cold the gauge shows cold, and a test light to the terminal doesn’t light. As soon as the thermostat opens the gauge goes straight to hot, and the test light lights. 3. On the o/s/f of the block, at the side, near No 1 plug, is a brass hex with a terminal, not connected to anything. Test light = nothing, engine hot or cold. So, have I got a faulty gauge, a faulty sensor, or is something wired up wrong? Is one of these sensors for an oil pressure gauge? I’m trying to sort out a thermostatic fan. I’ve got a rad (from the Defender I assume) with a sensor/switch just below the top hose entry, which has 3 wires, black, red & white. I assume that red should be a +ve supply, black earth, and white should switch the fan (I’ve used a relay), but I can’t get it to work, and without the temp gauge working it’s hard to know what’s going on. Can someone help please?

You need to phone these people.

Steve Parker Land Rover Spares, Spare Parts, Freelander, Defender, Range Rover Parts, Land Rover Conversions

the sender with 3 bolts is not temp sender its a cold start thermo switch,temp sender will be on rear passenger side of head ,thermo switch isnt used

But hes got a defender engine in it so the guage will mis-read the temperature surely?

maybe a bit but the one hes wired up is on/off thermostatic switch it never read on guage,you can get real cheap little adjustable resistors to rectify guage sender mismatch