I have a double slide dimmer switch in the entrance hall
One switch controls the lights in the outside farmer's porch and one next to it the entrance hall fixture

The hall fixture can also be turned on by another switch down the hall

Here is the problem

The porche lights do not get turned on [ tested all all bulbs and slid dimmer all way up] but the switch next to the porch one works just fine and same the one down the hall

I have not removed the double switch but it has a single front plate

Could this "half working and half not' situation indicate a wiring problem to the porch lights or could it still be that I need to replace the entire double slide dimmer switch ?

Thanks in advance

German

replace the entire double slide dimmer switch
What you have (I assume) is two separate switches. The one that turns the interior light on is a 3-way (with dimmer) switch that works in conjunction with the other switch down the hall.
The other is as single pole switch that turns the porch lights on and off.

Suggest that you turn the power off and remove the cover plate. Remove the porch light switch. Connect the two wires connected to it together with a wire nut. Turn the power back on. If the porch light come on the switch is defective. Replace it. If the light do not come on you have a wiring problem with the porch lights.

Thanks sincerely for your answer and help

It was a defective switch

German