Condensate drain gurgling?

[Wilkens390]

Have a Trane air handler (4TEE3C07A) for past 4 years. suddenly from a vent in pvc on the side there is a gurgling noise. If i put my hand over the top of the pipe it goes away. This just started past 2 weeks. I called the company we use for service and the guy thought the p trap was too small so made it much larger. Still have the noise. So I've read a bit and some say it may need to be primed? If so do i just pour water into that pipe (or even read vegetable oil)? Or can I just cap it with no ill effects?
I think I've attached 2 pics. the vent pipe is now taller and the p trap now comes down quite far. Hopefully these are clear enough for any recommendations.

[DOGBOY]

it will dry out over the winter and you will no longer here it when it does. In the summer it will fill up and you will not here it then either.

[Wilkens390]

So you're telling me it'll go away on its own. But I havent heard it in the past 3 years. So can I prime it with water by just pouring some in or can i cap it? if I put my hand over it the sound is gone but i as i lift my hand I do feel air pulling in so not sure if I should cap it or it needs to pull air.

[DOGBOY]

you can cap it in the winter but I would uncap it in the summer. You can not prime it as the p-trap is up from the vent. In other words if you poured water into it it would run away from the p-trap that you are trying to prime as the p-trap is uphill of the vent. The water should evaporate out of the drain and noise should be gone, if you could prime it you would have to do it every few days to keep the water in it.

[vstech]

can I get a picture of the trap? same position as your last picture, but bring the camera to the right until both sides of the trap are visible...

where does that drain? is it going to your plumbing, or exiting the house?