installed rear wing and disconnected 3rd brake light wing has led brake light built in. only thing is light out warning light comes on dash everytime I step on brake. any fixes or ideas? also is there any type of cap or something to put in hole where 3rd brake light was. thanks kelly

Is it a Volvo rear spoiler or aftermarket? If OEM Volvo, it's got the correct resistance BUT the original 3rd brake light needs to be disconnected so that you don't have two 3rd brake lights.
If aftermarket, it's very likely that it's got the wrong resistance. You could then just not use its 3rd brake lamp but one then might not see the original as it'll be obstructed by the rear spoiler.

its aftermarket, from spoiler depot. looks just like factory.

Just speaking as an electronics tech. I think you will have to put a resistor of correct value (ohms) and wattage in place of the brake light that you have removed. The fault sensing circuit is looking for a certain load (amps) which tells it that all of the brake bulbs are ok. Unfortunately the solid state LED brake light you have installed does not present a large enough load for the fault circuit.Hence you will have to put a resistor in parallel with it.

I'd be guessing if i told you what size resistor to install, But a good start would be the same or slightly bigger than the resistance of the original bulb. Also the wattage should be the same or slightly bigger than that of the original bulb. Make sure the resistor doesn't get too hot with the brake lights on.