OK, I live in the beautiful and wet Pacific NW. I have owned a 1988 Pontiac Bonneville SE with power moon roof since new. Water has been dripping inside on the passenger side front seat. I have fir trees and I think maybe the needles from the trees or just dirt has plugged the drain hoses that are supposed to be in the door pillars. I can't find or locate these hoses. Does anyone have any diagrams to show where these are or how to clear them out? I can't even see where they come out underneath the car. Where are they??? Any help would be greatly appreciated. GaryH

Check for the drains in the channel. The hose should come out near the wheel wells. Cleaning them out can be done with a little compressed air. But to much can pop the hose off the nipple and then you will need to go in and re connect it.

There are four drain hoses, one in each corner of the sunroof. The front ones run forward from each forward corner to the A pillar on each side, down the A pillar, behind the dash and exit at a nipple in the rear of the front wheel well, under the plastic fender liner. The rear hoses run rearward from each rear corner to the C pillar on each side, down the C pillar into the trunk, and exit at a nipple in the front of the rear wheel well, under the plastic fender liner.

Slide the sunroof rearward and pour some water into each front corner (you can see the drain holes). If the water comes out at the rear of the front fender wells the drain tubes are okay. Close the sunroof, then open it in the vent position. Pour water into each rear corner (you can't see the drain holes) and observe where it comes out. If it comes out the front of the rear wheel wells the drain tubes are okay.

If you have water dripping down from the headliner, one of the drain tubes has become separated from the connector on the corner of the sunroof assembly. This happens very easily since the hoses are not clamped in position. To fix this, you have to drop the headliner to access the connectors. Remove both sunvisors, the left grab handle, the left A pillar, and the left B pillar. This should allow you to drop the headliner enough to see the connections.

When you put the connectors back on, add a nylon tie strap or a small hose clamp so the tube doesn't pull off again.

Jack each corner up, remove the wheel, remove the fender liner to expose the drain nipples. Gently use a staightened coat hanger to clear out the mud and debris from the nipples until water flows freely.

If, instead from dripping from the top, the water is in the rear footwells (where the rear passenger'* feet go) one of the front drain hoses has come loose behind the dash. Let me know if this is the case and I will direct you to a post outlining how to fix that.

Based on your description (water dripping on passenger seat) I would bet one of the tubes has come off the connector at the sunroof assembly.

GaryH...where abouts do you live? I'm North of Everett and can give you a hand if your close by.

Not to thread jack here, but I have the issue with the water in the rear footwells. Can you point me to which thread addresses this problem? Thanks!

Maybe checking out this thread might help:
https://www.gmforum.com/1992-1999-91/water-leak-into-rear-seat-floorboards-286741/