Carbon Dioxide Generator

Repair and Trouble Shooting Tips



This is a common complaint. The pilot fuel mixture is a delicate adjustment because the orifice is so small and the flame so temperamental. Many things can effect how it functions in different environments and with different fuel sources. Fuel quality is a factor. Old fuel or cruddy fuel from the bottom of a supply tank could be troublesome. Bad fuel may contain waxy gunk that might deposit itself to plug orifice or restrict other parts from working properly. Impurities may cause fuel to burn poorly. Other factors such as elevation, humidity and even heat change the properties of the air and the oxygen content which effects the fuel / oxygen ratio. Sometimes we have to compensate for that by enlarging the orifice to make a bigger flame. The pilot should burn strong, clean and quiet. If it is lazy and yellow there is a blockage of the pilot holes or not enough air is passing through the bottom of the pilot burner head to feed the flame. Check for dirt or obstructions. Spiders will build nests in these small passages within the pilot head and clog flow especially after periods of non usage or storage. Store in sealed plastic bag. If the flame is loud and violent, there may be too much gas or pressure. It could even be blowing itself out. It will make a loud hiss. You will need to reduce the pilot orifice size. This usually fixes the problem. Rarely is the gas regulator at fault but it must not be overlooked as a possible defective component. Never adjust the spring tension under the cap of the regulator, and make sure the customer has not tampered with it either. Symptoms would be no gas or too much. Have a known good regulator handy to verify that the customers regulator is working properly. Hold the red button down and make sure all pockets of air from inside the hose are bled off and gas flow is consistent. Make sure the propane tank has not been overfilled. This can cause liquid propane to plug the line. If so, take tank outdoors and open valve to release gas for a few seconds, blow out the line and reconnect. The red button must be depressed for 30 seconds or until the thermocouple heats to operating temperature and can hold the pilot open. Make sure that the flame is hitting the probe sensor evenly and steadily. The sensor will get red hot and this is normal. Make sure that the thermocouple connector is snug and making a clean electrical connection to the bottom of the safety valve. Try a new thermocouple when in doubt. The thermocouple can be tested with a millivolt meter. Put the positive tester lead on the copper capillary and the negative lead on the contact. Heat the tip of the probe and measure the current generated. It should read approximately 30 to 40 DC mV. 15 mV would be at the border of acceptable output and may not be able to hold an old valve open sufficiently. If the pilot still fails to stay lit the safety valve may be malfunctioning. If the flame shuts off immediately when the button is released the magnetic coil is not holding the valve open. If it stays for a few minutes and then closes you will hear a click. It is uncommon to have to replace a safety valve, but it happens. Usually periodic pilot failure is resolved by increasing the pilot orifice size just a little. A little is a lot with such a small hole to begin with. Pass rat tail reamer gently through orifice to make slight size adjustments. Inspect flame size and characteristics for improved quality.



Hold down the red button on the safety valve for a few seconds and gas should start to flow out of the pilot burner head. Check for presence of gas by smelling. If gas is not present check to see if the pilot head or orifice are plugged. If the pilot seems OK then the safety valve would be the next device up line to troubleshoot. Remove fuel hose, hold down button and blow gently into valve inlet. The pilot orifice is very small but you should be able to detect a small flow through the system. Flow should stop when button is released. This seems to imply that the valve is functioning properly manually and that gas is able to reach the pilot head. If no flow is detected then the valve is broken or plugged.



Gas flows through the safety valve and on through the solenoid valve to get to the burner orifices. Obviously the burner needs to be clean and slots clear. The gas is metered through the orifice by the size of hole and then ignites in combination with the oxygen drawn in through the air ports at the foot of the burner. The orifice size must be adjusted to produce a clean blue flame generally about 1/2 inch high evenly across all the slots of the burner. Be sure all air has bleed from the hose and gas is present. Make sure the transformer is plugged into a working power source and that it is working properly. Usually it will cause the switch to illuminate. The switch does not need to illuminate to work but it is a good indicator of power supply operation. The light could be burned out. That is not critical to the function. Check with a meter for 12 vdc current from the transformer. The switch may be bypassed for the purpose of diagnosis. Make sure the red power switch is in the "ON" position. You will hear a audible click when the power switch is turned on and the electric solenoid opens. Solenoids will get very hot to the touch and that is normal. Incidentally, solenoids can also get a small piece of debris in the valve seat prohibiting them from closing all the way and the burner may flash or attempt to partially light even when it is supposed to be off. This is often cured by holding down the red button and turning on the solenoid and blowing the valve body out with low compressed air. On the models 18 and 36 only check that needle valve is open. One turn is fully open. The burner needs to be level to burn properly.




Check for adequate fuel supply. Make certain there are no loose or broken wires anywhere in the plugs or connections. Check that needle valve (when applicable) is open enough to support a strong flame. Check timer and power source operation. Make sure that the electric solenoid valve is opening properly so gas can pass to the burner. Check to see that the burner is not dirty or plugged and that the orifices are clear. The flame can be blown out by fans or brisk air currents entering the housing. If the pilot flame is extinguished the safety valve will within one minute shut down the fuel and cause the main burner to go out.



Dirt or residue could constrict burner orifice. The burner orifices may be to small or even to large. If black soot is present this is evidence of improper fuel/oxygen mixture. Soot is fuel residue from unburned fuel. This usually indicates a lack of oxygen to the flame. This will create a bad smell and it is also creating carbon monoxide instead of carbon dioxide. This of course is not good. Burner slots or tube may be clogged. Low fuel pressure due to faulty regulator or nearly depleted supply. Contaminated fuel supply. Build up of gunk in any part of valve body assembly. Lack of oxygen content in room due to inadequate fresh air intake. Excessive air movement or gust from fan or ventilation. Generator not level. If the burner is not horizontal the flame will burn uneven across the slots. If the flame is way too big it is possible that you are trying to burn propane in a natural gas orifice (NG orifices are much larger holes) or vice versa if the flame is way too small. Propane generators will not work on natural gas and natural gas generators will not work on propane because of the orifice size differences. Otherwise there is no difference in the two models. Units may be converted back and forth by fitting with the proper pilot and burner orifices. The regulators are also different for each fuel type.


Basic Valve Assembly
(Typical model CD-3)

1. Hose to pipe adapter

2. Safety valve

3. Thermocouple

4. Pilot burner head

5. Pilot orifice

6. Solenoid valve

7. Burner orifice

8. 12 vdc power

valve-assy1-opt.gif (22358 bytes)


This information is provided for the purpose of diagnosing and repairing Green Air Product CO2 generators both propane and natural gas models CD-3, 6, 12, 18 and 36. For further assistance contact 1-800-669-2113 or 503-663-2000 or e-mail to


*** Green Air Products Inc. P.O. Box 1318 Gresham Or. 97030 USA ***

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