My Peugeot heater inside the car goes hot then cold then hot then cold. This happens specifically when I stop at traffic light. Please help.
First thing to check would be the coolant level.
The next thing is to find and fix the leak if the coolant level is low. If the leak is minimal you may be able to get by with adding some stop leak to the cooling system. This is what I use:
If it is not low on coolant the next thing would be to check the blend door actuator, specifically if it is vacuum operated. Look at the back of the selector switch where the vacuum hoses attach and also check each hose individually for cracks.