My 95 GMC Sierra (3/4 ton) has an annoying leak following a rain or snow fall. There will be a small amount of water that will leave a small trail on the right floor mat toward the door jam. Last year in the winter it filled with water (blower housing) and froze, then when I turned on the blower it shattered the squirrel cage. Don't want to repeat that this year. It (the leak) seems to be coming from the blower housing. I have read some about this problem here in the past but can't find the thread (it might be too old). Where is the typical problem that causes this, is it a leak under the cowl or where. I've looked and I am baffled.
Any help accepted, and you have my grateful thanks of course.