3.5v6 tempt gauge is not moving as engine warms?

How do you know its wrong? What have you done to establish that opinion? Gauges are pretty reliable, you need to check the sensor on the engine, usually on the thermostat housing. They are cheap and easy to replace by someone with a little experience. Don't do it with a hot engine. If you have an old style mercury thermometer, check the water temp when warmed up against what the gauge says. Thats warm up not full running temp. 10 mins or so of idle or until the gauge starts to move.

Sounds normal. If the gauge moved further over, it would indicate an overheating problem, wouldn't it? Check that engine is at normal operating temperature after it warms up. If it is running too cold, your thermostat might be stuck open.

If the engine is not warming up, the thermostat may be stuck open.
If the engine is warming up and the gauge is not moving, the problem could be the sending unit for the gauge or the gauge itself.

the timing could be off you may have to have it checked and fixed hope this helps

I'm not a Peugeot expert, but do you know if the engine is warming up normally ?
The thermostat could be stuck open, or the engine could be low on coolant, or the sending unit for the gauge may have failed. If the engine is warming up you should be able to ground the wire to the sender and watch the gauge move.

disconect wire from temp sending unit
if that stops gauge moving , u most likely need to replace sender unit
they are not expensive
if after replacing sender unit gauge still does it, u need to replace the gauge

Check the gauge by holding in the trip odometer reset button and turn key to run,hold button for 10 seconds this will iniate a diagnostics on all the gauges,and lights if gauge doesn't move during this test replace gauge,if it does move then check the wires on the plug at the engine coolant temp sensor (ects) you can check the sensor by using a ohms meter by unpplugging it and check ohm's or resistance when cold and then start engine as the engine warms up the ohm's reading should gradually lower as the sensor is a thermister and as it warms up the resistance will drop.

Hello,

I would also be compelled to suspect the lack of Fuel, towards from the Engine, normally the Carburetor combines fuel and air, into a highly volatile mixture. So when its hot, I would think it evaporates so quickly before it reaches the engine. Try to tighten any pipes, or look for leaks around the Carburetor.

1st check the coolant level. If it's low, what you describe will happen. If level is ok, let me know, and include info on engine temp gauge--how long to warm up, is gauge at warm up low temp range, normal, or hot?

You might check the coolant level after the engine cools,if it's low add 50/50 mixture of coolant and water. Keep an eye on the level to see if it happens again. You might have a small leak in the system. Good luck