Gee, here I am again asking a Question on my 99 TahoeZ56 Police 5.7 L engine. This weekend, I had my Tahoe parked inside a heated Garage for few hours ( -20 C outisde) , then drove outside. I had the heater on and fan speed in level 3. Everything working fine. I made a stop at the coffe shop and came out about 20 minutes later, no fan blowing. I turned to all the positons , nothing at any speed. I left it on level 3, and drove manybe 10 minutes and it started working again. Today it acted up again, not working for about 10 minutes then working fine. On the way home from work, no blower at all on any speeds. The 30 minute drive, nothing came on, gloves and fur cap/flaps down all the way home!! I figured maybe having it inside the heated garage, some ice melted and ran down somewhere in the blower area, and once outside in the -20 it froze up once I turned it off at the coffee shop.. Where would I start? fan switch ? blower motor ? or resister. I guess I will have to buy a shop manual for this truck, having alot of gremlins popping up. The truck has 266,000 Km/ 160 ,00 miles. Thanks for any help. Signed.. Cold -frozen Canadian Mountie in Saskatchewan.