My Pulse 21 furnace sounds like it wants to come on ,but shuts down after a few seconds.The module light is on saying system is working.My programable thermostat gives me a message (-AC).The thermostat comes on saying system is on then clicks back to (-AC) AGAIN.Have turned power off to furnace and timed it for about a minute.Turn it back on and system will start operating again.Sometimes for a week or maybe a few days.Technician has been out and checked all wiring and circuits and feels even though the module light says system is working that it may be defective?This module costs $225.00 and takes 3 weeks to obtain. Could it be the module board or am i wasting my money? THANKS, RON PS-The furnace is 10 years old and has been a problem from the beginning.Very noisy for a furnace