Toyota Repair: 89 Toyota Celica heater, auto air conditioning, heater control valve

Question
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Followup To
Question -
My heater blows cold air most of the time but on occasion will blast out hot air. On the odd occasion it does blow hot air the minute you touch the controls it blows cold again. Any ideas of where to start looking or is it possible to hard wire something to the vent to get heat? The fan blows on all settings and all other settings work just no heat. We had engine rebuilt 3 years ago and have 80,000 km on rebuild but problem just started this year.

Thanks,
Gail Dand
Answer -
Try replacing the heater control valve under the hood on the firewall, there is also a good chance that the heater core is partially restricted, by the way, does it have the electronic dashboard control panel with push buttons or is it all manual operated and does it have auto air conditioning.

Ted,

In response to your answer - No it does not have air conditioning and Yes it does have push button dashboard control panel. I took your answer to my mechanic and he took the radiator cap off while the car was idelling and I got heat instantly and when he tightened it I lost heat but the second time he did it after topping up fluid levels I had heat. For the last three days I have had heat 2 of the 3 days but not consistantly and my mechanic thinks it could be an air lock in the system. Is that possible and if so what do you think would cause it and what should we do to correct it? Thank you for your quick response and look forward to hearing what you think these symtoms sound like.

Gail Dand

Answer
Yes it is possible that there was an air pocket in the system, this is normally caused after draining and refilling the cooling sytem, it can also be caused by the engine overheating so make sure that is not the case, another cause may be a sticking thermostat, try replacing it and see if it helps.