Goodman 80% affue Furnace with front cover off
man Air Conditioner
Uncased Evaporator Coil
Evaporator Coil mounted on top of Furnace


The Furnace and Air Conditioner are separate but interactive systems. The Furnace can operate with out the Air Conditioner working.  The Air Conditioner  can not operate if the blower in the furnace has failed.

What the furnace does for the Air Conditioner:

The Thermostat gets operating low voltage of  24VAC from a step down transformer in the furnace.

This is usually routed through the control module and depending on the Call for Heat or Air Conditioning it directs the appropriate system to run.

The Air Conditioner requires the Furnace blower and control module in the Furnace to be in good order.

If these components are not operating properly the Air Conditioner will not function.

Note:  An Air Conditioner's operational state can not be determined unless the furnace blower, and control systems are working properly.




However the outside unit may continue to run with out the Furnace blower working causing the Evaporator coil above the furnace to ice over and drip water that will possibly escape the drain system creating water on the floor around the furnace.

Note: This is not the only thing that will cause water leakage problems.   Restricted air flow through the Evaporator coil (on Top of the Furnace) or the Condenser coil ( outside unit ) can cause this problem there are other circumstance that could cause this to happen as well.

If you can hear the Furnace blower motor running and you can't feel very much air, warm or cold coming from the vents in the house.  Then it is almost certain that the evaporator coil mounted to the furnace has iced over and air can not pass through it properly .




This is indicative of a low refrigerant charge, if the air coming from the vents seems to be at the normal rate but not cool then the refrigerant is extremely low or the unit outside that has a Fan motor and a Compressor motor is not running at all or one of the two motors has failed to operate.

Both motors have capacitive start systems. A failed Capacitor could be the reason for an inoperative motor

The compressor motor is hermetically sealed and is beyond field repair.   A new compressor would be required and is labor intensive to remove and replace, in all but a very few circumstances it would be better to replace the whole AC unit.

Refrigerant replacement required is measured in pounds.   AC units depending on the size can require from 5 to 10 lb, on average most use about 3 to 4 lb.

 This is only a general description of Air Conditionig sytems possible problems, it does not cover all possibilities.


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