Jim Grant's Tech Tips

'89 Nissan Maxima

Q: I changed the thermostat, and I still don't have any heat. When I turn on the heater, it starts out warm, and then goes quickly to cold.

A: Is the temperature gauge on the dash indicating that the engine is warming up correctly? Is the coolant level correct? If the answer to both questions is yes, then it is possible that you have a restriction in the hoses, control to the heater core or the heater core is restricted. If the coolant flow to or through the heater core is restricted, it is common to have heat for a few moments when the heater blower is first turned on. Then the temperature drops. You’ll need to have a technician check the coolant flow rate to the heater core. The solution may be as simple as back flushing the heater core or as costly as a replacement.