Defroster must be running full blast in order to have any heat or a little defrost in van. Turn it on “heat” only and Windows are frosted over within 5 miles of highway driving.
RESPONSE
First thing to check would be the coolant level. If the cooling system is low it makes it difficult to heat. This is the most common reason for your situation. If the coolant level is full look for a stuck thermostat.
Engine Coolant Thermostat Replacement
Removal Procedure
- Remove the air cleaner and duct assembly. Refer to Air Cleaner Inlet Duct Replacement in Engine Controls – 3.4L.
- Drain the coolant until the coolant level is below the thermostat. Refer to Cooling System Draining and Filling .
- Remove the crossover exhaust pipe. Refer to Exhaust Crossover Pipe Replacement in Engine Exhaust.
- Remove the radiator hose from the thermostat housing. Refer to Radiator Inlet Hose Replacement .
- Remove the thermostat housing bolts and clean any sealer from the bolt threads.
- Remove the thermostat housing and gasket.
- Remove the thermostat.
- Clean the mating surfaces.
Installation Procedure
- Install the thermostat.
- Install the thermostat housing and gasket.
- Install RTV sealer, GM P/N 12378521 (Canadian P/N 88901148) or equivalent, to the thermostat housing bolt threads.
- Install the thermostat housing bolts.
- Tighten
Tighten the bolts to 25 N·m (18 lb ft). - Install the radiator hose to the thermostat housing. Refer to Radiator Inlet Hose Replacement .
- Install the crossover exhaust pipe. Refer to Exhaust Crossover Pipe Replacement in Engine Exhaust.
- Install the air cleaner and duct assembly. Refer to Air Cleaner Inlet Duct Replacement in Engine Controls – 3.4L.
- Fill the cooling system. Refer to Cooling System Draining and Filling .
- Inspect the cooling system for leaks. Repair as necessary.