HiCustomer Thank you for asking your question on Just Answer. The other Experts and I are working on your answer. By the way, it would help us to know:-Could you explain your situation a little more?
Is this a combination AC and heater?
What is the model number of the furnace?When was the last time the furnace was professionally serviced?What is the age of the furnace?Do you have a digital camera that you could use to send pictures of the furnace if needed?Thank you again for trusting us with your problem. Please reply as soon as possible so that we can finish answering your question.
My first advice is to get a new furnace service man. The parts can and should be checked before replacing them. You should never be charged for a part that does not correct the problem. If you have a combination AC heater and have a fan switch make sure it is on auto not manual. I have seen the fan switch on the thermostat cause the problem. Disconnecting the wires on the thermostat is a very easy to check for this possibility. From what you have told me about the service man I do not have much faith in his test procedures. My first though is a defective fan switch or a sequencer. It is possible to get a defective new one. Click here and here for information on testing components on your furnace. If you could provide me a link to the electrical schematic that is the same as yours it might help.
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