HI - I have a 1985 Cutlass Supreme 3.6 engine. The other night the heat gauge was not moving and there was no warm air coming out of the heater. It was working and we stopped for dinner for about 45mins came out and was not working.

We replaced the thermostat and now the gauge is working. The problem is the heater is still not blowing out hot air.

Any thoughts on what is wrong?

Thanks,

Elizabeth

is any air blowing out?

is any air blowing out?

Shekky,

Yes the fan is blowing air but it is cold to warm if lucky. I try adjusting the temperature on the heater too and still no luck. I actually set it all the way to 90 degrees. I have also tried all the settings - Bi-Level, lower etc.

Thanks for your help.

Elizabeth

do you have enough fluid in the rad?

Shekky,

Yes, the radiator if full and there is fliud in the overflow as well. I checked this all when replacing the thermostat. I apologize for not giving all the relevant information in the first post.

This is what is so baffling. The thermostat is new, fluid is good, the temperture gague inside is now working, the heaters fans are blowing but not hot air. Also, there are no leaks. I hope it isn't anything serious.

Again, thanks for all your help.

Elizabeth

maybe need a heating core replacement

i dont think its the heater core. they dont usually clog up as much as leak. and you would definitly notice the leak.
when you change from cold to hot, can you hear the vacuum system changing over?

i dont think its the heater core. they dont usually clog up as much as leak. and you would definitly notice the leak.
when you change from cold to hot, can you hear the vacuum system changing over?

Shekky,

I will need to check this. There definalty has not been any leaks. I will get back to you.

Elizabeth

My 1988 Olds Cutlass Supreme heater quit working. I found and repaired the problem, and recommend the following for you to troubleshoot.

The Oldsmobile heating system works as follows: two hoses (inlet and outlet) run from the water pump through the firewall to the heater core. Some vehicles have an in-line shutoff valve.

The heating system controller has three functions: fan motor speed, temperature, and directed air flow (lower, bi-level, upper, defrost). Directed air flow is pneumatically controlled using engine vacuum to reposition doors inside the ductwork. By removing the glove box insert and/or insulated covers under the dash, the pneumatic actuators are visible and their operation can be checked. In older models, the controller sends an electrical signal to an electro-pneumatic converter box that connects vacuum lines to the pneumatic actuators. In newer models, the controller is pneumatic with vacuum lines connected directly to the actuators. Temperature control is also accomplished by repositioning a door that mixes heated air with outside air. However, this door is actuated by an electric motor.

To troubleshoot for no heat, you should first check that the fan motor and temperature control motor are working. Without starting the vehicle, turn the ignition switch on and operate the fan and temperature controls, one at a time, and listen for motor operation from under the dash. The temperature control motor takes several seconds to move from extreme cold/hot positions.

Next, check if the heater core is getting hot. Run the engine to normal operating temperature and carefully touch both heater hoses (inlet and outlet) at the firewall. If they are cold, there is no water flow, and either the water pump, thermostat, or inline shut-off valve (if installed) is defective. Look up the specific model and year whether the heating system has an inline shut-off valve. Note that a defective water pump or thermostat will likely cause low heat, not no heat. If the water pump is defective, the engine may be overheating. Check the water pump (bearings) by disconnecting the belt and spinning the pump. Rotation should be smooth. If the thermostat is defective, engine warm-up would likely be prolonged.

Finally, check for directed airflow (lower, bi-level, upper, defrost). Remove the glove box insert and/or the insulated covers under the dash. With the engine running, check the pneumatic actuators for operation. Note that defects in the directed airflow system does not affect temperature, but this is easy to check.

For safety, when power is not needed, disconnect the battery when working at or near electrical system components.

If you remove the insulated covers under the dash, I recommend removing the cover to the heater core for cleaning because dirt will accumulate over the years. It may be necessary to disconnect the gas pedal mounts and under-carpet center duct section to remove the heater core cover.

If the temperature control motor does not work, disconnect the wire bundle from the motor (under the dash). There is a red (+ 10 volts) wire, black wire (- ground), and blue wire (+ 2 to +10 volts temperature control range). Using a volt-meter, check the wires with the ignition switch on (engine not running). If these check okay, the controller is good and the motor is likely defective. I recommend reconnecting the wire bundle to the motor and rechecking its operation because the problem might be a poor connection. Otherwise, remove and repair (or replace) the motor. Heater system components are reliable and may just require cleaning and lubrication. To access the temperature control motor for removal, it may first be necessary to disconnect the mounts holding a relay box and the electro-pneumatic converter box (on older models).

If you overhaul the temperature control motor, the spline gear must be re-aligned. The duct door is spring loaded to the "cold" position. Before installing the (four) motor case screws, connect the wire bundle, turn the ignition switch to on, set the temperature to cold, and check for spline alignment. With power off, disconnect the wire bundle, open the motor case, and reposition the spline gear and repeat the procedure until alignment is achieved. Close the case with (four) screws and install the temperature control motor. Before proceeding, check its operation, then re-assemble the heating system.

my 83 wasnt blowin hot air, but it had a antifreeze leak, check out yur heater core, a hell of a tough thing to get to