I have had this heater for approximately 3 years. It worked great for the first 13 months. ( Warranty expired after 12 months). The millivolt generator gets burned out after about 3 months of use. We have replaced it at least 3 times already and getting ready to replace it again or buy a new heater. The flame must get too hot and eventually the generator has no output to heep the pilot lit. Bench testing the unit after it does not work will send a 500 mV signal, but this is with a high heat propane or MAP gas torch. It does not send a signal with the pilot button held, even for 5 minutes. Why do these units continue to burnout. There is only one manufacturer - White Rodgers. Should there be some sort of deflection shield installed?
I have a Cozy CDV156B propane wall heater in both my office and workshop. 2 weeks ago I had the sam problem as mrtrick2, held off on buying a millivolt Generator and just yesterday, my other heater did the same thing. The gas line is fine, the pilot lights with the igniter when I hold in the pilot knob, I hold in the knob for anywere from 2 to 4 minutes and the thermocoupler just will not get hot enough or recoginze the heat, I am not sure. The pilot flame is located perfectely at the generator.
Having read mrtrick2's post, I am not sure what to do now. Really strange that it has happend now to both heaters though. HELP !!!!!!!
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Re: Millivolt Generator burnout
I would check the pilot orfice to make sure you have enough of a flame to heat up the generator. You can buy a orfice drill bit and drill it out one size. The pilot should hit the generator toward the center. You should be able to buy a new orfice for the pilot assembly from the place you bought your heater.
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look in back of the heater where the fuel nozzle goes. you will see a plate with a bunch of holes, the ignitor and the fan. also there is a little button with two wires on it. these wires connect to two spade terminals on the millivolt generator. its sensing bulb is near to the fuel nozzle. the other end with the gland nut goes into the main valve body. when the heater is on, the flame hits the millivolt generator and makes a very small DC voltage which goes through the little disk [an overload] then to the main valve solenoid. if the millivolt generator is good then there is a voltage at the main valve solenoid and it keeps the valve open. in your case it seems 1) the overload is open 2) the generator needs to be replaced. please go to desatech site and order a new generator.
the heater makes use of a millivolt generator which generates a small dc voltage (500-750mv) that is applied to the pilot valve of your main gas valve. when you light your pilot, the flame bathes the generator with a flame. after a delay you release the pilot button. if the generator is working, the pilot valve will stay lit. if the generator is not working the flame will go out as soon as you release the pilot button. change the generator.
two things come to mind here. the high limit shutoff and the millivolt generator. the hi limit cutoff is a thing that looks like a metal pill with two wires coming off it. those two wires connect to the two tabs on the millivolt generator cappillary. its purpose is to keep the millivolt circuit closed. The millivolt generator produces a very small (750 ma) voltage which is in turn connected internally in the gas valve to a small electromagnet. with a flame on the voltage is generated and keeps the pilot valve open. replace either or both devices.
the little tube that is in the path of the flame is a capillary tube that houses a thing called a j-k thermocouple. it is nothing more then a millivolt generator that produces a very small dc voltage that actuates a very small electromagnet in the main valve. when you start the unit you need to push in a button, correct? when you release the button the valve should stay open, but you say it doesn't. the millivolt generator needs to be replaced. try doing a search for "dynaglow" heaters or www dot desatech dot com for a new generator.
I doubt that it's the pilot generators themselves that have been failing They normally last for years through any temperatures that a pilot flame can produce. More likely, the gas valve is bad and is trying to draw more current than the generator can supply. You could verify that by connecting one of the "failed" pilot generators to a known good gas valve.
If the problem is consistent you could try measuring the resistances of the two electromagnets in the gas valve. If you compare your readings to those for any other gas valve of similar type (same brand or not), they should be in the same ball park. 12 ohms and 10 ohms are in the same ball park; 10 and 2.3 are not. If the problem is not consistent but intermittent, see if by any chance it (a.) gets better when the valve is stone cold and worse after it's been drawing current for a few minutes, or (b.) gets worse when you mechanically disturb the screws and terminals on the valve or the wires attached to them.
That "750 mv" is just a number. In practice, 400 mv is a pretty respectable output. Even 250 mv is usually enough to operate the electromagnets, provided it doesn't drop much lower than that and nothing else goes wrong.
When the pilot flame is too small, the adjustment on the gas control is rarely the problem (or the solution). Much more often, the orifice (located in the inlet of the pilot burner) is clogged and needs to be reamed out. A #79 drill bit is about right for the job, if you have the patience and dexterity for it.
Good luck, mrtrick2 or anyone following in his footsteps.