I have a goodman furn. That is vented to the exterior with two 2" pvc pipes that turn into one on the exterior with a bell that allows intake and outflow all in one . It seems like when we get a lot of moisture on the outside like snow it quits running and the sensor blinks three times. The excess moisture is draining into a troft with another line feeding back into the furnice that also lets water drain back out into the troft after it quits running each cycle. If I turn the power switch on and off a few times it will light and work fine sometime for weeks at a time sometimes for just a day or so. Any help would be great thank you.

You have a concentric exhaust which is OK to use with your system. You can try to check for blockage but it is difficult with that style of venting. The vent pipes should have been installed per the manufactures instructions and if they were not then problems do happen. Three blinks on a Goodman can be the venter end switch or on later units the pressure switch that activates the unit. When you turn the power off and back on your are just reseting the safety control built in on the circuit board.

Since it is possible the PVC pipe may need to be disconnected or cut to see if there is any blockage or if there is a pipe pitch problem you will need professional help.

How high from the ground is the vent? If it is to close to the ground they can have problems with snow.