On my previous post “It was the Valve” below, I reported that changing the valve stem, and cleaning and manipulating the coil contacts fixed the problem of the trap failing at high case temperatures. I am grateful for that.
This season starting early June, the trap exhibited a new anomaly. After warming up to about 120°C and running for a period of time, the trap combustion temperature declined to about 75°C and stayed there. This happened when the case temperature rose to about 43°C. (This trap has the wireless controller installed, and I record and display the data continuously, so have a complete record of the operating conditions, including the external case temperature and humidity sensor.) The trap was catching very few mosquitos, and none were observed alive after the trap was running at 75°C for a few hours. Accordingly, I have to conclude that the trap was “not working.”
I fiddled with the contacts, removing and cleaning them (there was a small deposit of some dark material on the female contacts visible under the microscope), and reassembled. This did not fix the problem. Then I substituted sealing tape for the valve mechanism to bypass the valve, and that did not make any difference either! A new issue!
Fortunately, the wireless controller has remote control troubleshooting commands. One turns on the ignition, and another turns off the gas, each for a specified number of seconds. Turning the ignition on when the temperature was 75°C had no effect. Turning the gas off for about 20 seconds initially resulted in a combustion temperature rise, which seems backwards. It is as if there is something blocking the gas flow that relaxes as the gas pressure is reduced, letting more gas into the combustion chamber.
I restarted the trap by turning the gas off for about 50 seconds plus ignition on for about 90 seconds. The temperature rose to over 110°C, but the result was short-lived. It fell down back to 75°C. No mosquitos were caught during this period. My raw notes:
Reinstalled the valve core, then attached auto tire pump, and pump delivered 80 psi, falling to 75 psi or so. This is not necessarily low enough, the nozzle might be clogged. Re-attached the tank, used the orange reset tool on regulator, and restarted. Experiment of ignition on 120 seconds with gas off 20 seconds near end restarts combustion from 77° to 115°C. Temp first started to go up when gas was turned off … !!! During this time Temp/Hum declined from 45° to 44°. Might be a clogged nozzle or gas passage causing burn problems. Or the regulator??? But how could the regulator be affected by case temperature?
The regulator cannot be affected by case temperature. However, the gas reset tool could affect the old style regulator, which might be flaky, delivering the wrong pressure. I don’t know what the right pressure is supposed to be. The old style is adjustable, and the end cap fell off and was lost a few years ago. Perhaps I should replace it, but the new regulators have fixed pressure of 11 column inches of water, which would not work if the Defender needs a different pressure.
So what could the case temperature have to do with the gas flow? It could be the nozzle or some obstruction in the passage between the valve and the nozzle. I suppose I will have to tear it apart, again. But for now, the trap is on and working perfectly. Not too many mosquitos, though, but there are always a few live ones whenever I check. I suppose I mostly decimated the population with last year’s incredible bumper harvest. At least I am not getting bitten. The next time I notice a fall, I will try the gas reset tool alone without the tire pump, and see if that helps. Another year, another mystery. Such fun!