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Heating, Air Conditioning, Fridge, HVAC/Furnace blows cold air continusly .


Hello Friend!  

I have a problem with the natural gas, forced air dual zone heating system (NO AC) in my 2 story 3100 sq. ft. home.  It uses a Goodman Model GMP100-5   Serial #  9503098429 ,  100,000 BTU IN /80,000 BTU out Horizontal flow furnace.

The system employs a  “Two Zone HVAC Controller”   “with thermal equalizer for standard gas/electric systems”  controller.  It is a ZTECH brand, from Gold river, Ca.  Model  ZTE2S  Part #  001-00240          24 VAC .  

When calling for heat, the system operates correctly, EXCEPT now and then it will supply warm air to zones 1 &2, when only a single zone is calling for heat.   The electrically actuated Zone 1/Zone 2 damper has a history of “sticking” in 2 zone operation.  I have thus far ignored this intermittent problem.

The MAIN PROBLEM, is when NO heat is called for the furnace blows unheated air, continuously.  Turning “off” the thermostats, and removing their batteries does not stop the air flow.  I must turn the  circuit breaker off, or unplug the furnace to shut the fan.  

I did a visual inspection and the “Two Zone HVAC Controller” appears to NOT be flashing a trouble code, in the malfunction mode.    I “tested” the 4 “rollout switches” by removing the wires (to open the circuit) .  I then jumpered the rollout sensors to “close” the circuit.  I did this one sensor at a time, with the furnace in malfunction (fan blowing constant unheated air), no heat called for.    This did not stop the fan from blowing.  

The furnace had 1 red LED on it’s circuit board, which glows steady.  

Any help would be appreciated.  

Thank you, Mike Celi


If you have a time delay type fan relay possibly the normally open contacts are either welded shut ( keeping your blower on ) or possible your always supplying 24 volts to your fan relay . If your handy with a ohms meter find the power contacts and pull all wires off the relay marking where they hook up to ,then ohm out the contact point. It should show an open with no power. Double check that you do not have 24 volt ac at the fan relay coil when nothing is calling and unit power is on .  You can also remove the G wire and R wire at the t-stat to check if the fan shuts off.If your blower motor turns at a slower than normal RPM you may have a grounded motor, but it would concentrate on the fan relay  

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40+ years diversified experience.An HVAC/Refrigeration Self Employed Contractor since 1986. NATE Certifield. Answer questions pertaining to Residential and Commercial Air Conditioning , Warm Air Heating, Heat Pump systems.Mechanical and Electrical troubleshooting of these systems.Be as detailed as possible when describing problem.Packaged unit or split systems.No appliance questions.


Installation and Troubleshooting, Mechanical and Electrical, in following areas, Refrigeration ( Walk In and Reach In Coolers and Freezers ) Commercial Roof Top and Packaged Heating/Cooling ( Natural Gas,Propane, Electric, and Heat Pumps ) Computer Room Air Conditoning Systems,Commercial Residential Packaged and Split Systems Air Conditoning and Heat Pumps.Warm Air Oil , Natural and Propane Gas Heating systems.

Graduated from Private Technical School in 1975. An HVAC/Refrigeration Contractor . Have Unlimited Heating/Piping and Cooling Contractor License.Limited Sheetmetal Contractors License.NATE Certifield. York Certifield Master Heat Pump Technician 1986. Served 33 years combination Active Duty Air Force , Air Force Reserves and Air National Guard in the HVAC/Refrigeration Shop/Mechanical Shop. Troubleshooting/Installing HVAC/Refrigeration Equiptment Worldwide. Retiring in 2003 as a Senior NCO ,and a Mechanical Superintendent.

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