1970 Oldsmobile 98 No Heat from heater - fan blows fine

  • 1970 OLDSMOBILE 98
  • V8
  • 2WD
  • 86,000 MILES
My 1970 Oldsmobile 98 convertible has no heat output from the heat or defrost vents. Several weeks ago it was working fine, then one day, there was no heat, the next day there was heat, and now (for the last 2 weeks) there is no heat at all. The fan runs fine and there seems to be plenty of air flowing through the system. When this problem is happening, if I place the temp control lever in the HOT position, there is a high pitched humming noise coming from under the dash (that I have never heard before this problem started). The noise is too quiet to trace down with the engine running. The noise does not happen with the engine off, key in RUN position and the heater turned ON. All the flaps in the heater box seem to be working exactly as the factory Oldsmobile Repair Manual indicates they should (the flaps and levers that I can see) There is plenty of vacuum at the heater control valve mounted on the engines intake manifold. The engine seems to be running at normal temp's as the radiator hoses get hot. However, the hoses to the heater core do not get as hot as the radiator hoses, but they do get warm. Coolant level is right where the manual says it should be and there is no loss of coolant or any signs of leaks. Cooling system was flushed and all hoses were replaced approx. 1 year ago. Water pump was also replaced at that time. Has anyone heard or seen this before?
Do you
have the same problem?
Wednesday, November 10th, 2010 AT 11:50 AM

1 Reply

Test the thermostat and check the heater core
Was this
Wednesday, November 10th, 2010 AT 1:24 PM

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