Well, I'm back again. MiniMax NT (400kBTU) Model 400DV with 6800 controller. This is an early model, ~2002 vintage - no LED error code display on this dinosaur. So, this week's problem: heater is short cycling - burners ignite for about 3-4 seconds then the gas valve kicks off, flames go out. 3 burners were not working, but I cleared all the orifices and they are all lighting now (but all still going out). Blower was making a horrible racket, but it ran like that for weeks until the whole heater stopped heating this week. Finally tore into the blower today. The impeller rusted all to hell, missing half of the vanes (see pic). Ordered a new one, but cobbled this one to run a bit longer in order to diagnose further. Front Panel Lights (see pic): Tstat: Green Aux: Green Press: Green Heat: OFF Power: Green Service (Exclamation Point): RED Internal Lights (see pic): PV: OFF (< anyone know what this one is for?) Tfuse: Green HiTemp: Green Igniter seems to be functioning (it fires seemingly fine). Replaced the flame sensor today. I assume new one is working correctly. I thought this was the problem for sure....but no. Note: My gas company has been working on the gas lines in the neighborhood recently. I've cycled the burners maybe 10+ times, thinking of air in the line, but problem remains unchanged. Questions: - What does the Red Service LED indicate? - What does the PV LED (inside) indicate? - If the blower is not blowing at full power, could that be the problem? (It most definitely is not at full power as it the impeller is totally shot). The pressure sense hose is connected from the blower to the sensor, but I don't know about the condition of that sensor. - Could this just be air in the gas line? Anyone have any other guesses/suggestions/ideas? My blower impeller finally exploded, so I won't be able to test again until I get the replacement on Monday. Collecting ideas for the next round.

When was the last time it actually fired? If the gas line was open, you will have air, but you said you smelled gas. You could have a rusty pilot orifice too. On that heater, if you are getting spark and smell gas, the mechanics of the safety loop circuit are working fine or you would not get a spark. You can loosen the pilot tube from the valve and then turn the heater on until you hear the valve click. Gas should come out of the 1/4" hole. If it does, that portion is ok. Put it back and tighten. Fire it back up and listen for gas down in the pilot area. DO NOT PUT YOUR HEAD THERE AND IF YOU HEAR THE SPARK STOP, MOVE OUT OF THE WAY QUICKLY! If it continues to spark AND you smell gas, you have a further diagnosis to do. If you have gas at the pilot and spark, you have to have flame unless the spark gap is way out of whack. If you have spark and no gas, it is a plugged burner, bad ignition module or bad valve. Those tests need run. For the valve to be bad, you would need to have flame at the pilot and hear a click at the valve with no ignition. that would still not narrow it down w/o tests. Let's assume spark and no gas. Put a test lead on the valve ground and the PV terminal on the gray ignition module with the heater on. No voltage (24) there means a bad module. Let's assume, spark, gas and no flame. That would be a pilot issue. Let's assume, spark w/flame and no ignition. You need to confirm where the 24volts stop. It could also be aloose ground. You can put a test lead on the valve ground and then put it to the mv terminal on the gray ignition module. Voltage there (24)indicates the module is good. Put the lead down to the mv terminal on the valve. Voltage there (24)and no main valve operation means your valve is toast.

I have a question about the ignition there is a red light on the ignition box, Is this light supposed to be on or off when you power up the heater because when I turn it on the light is off. thanks again

My MiniMax is so old it doesn't have a controller with any type of display - so, unfortunately no codes to work from. However, poolguiynj - you nailed it. I pulled out the middle jet and tube...and as soon as I turned over the jet a very chunky spider ran out. He left behind a pretty tough web in the orifice - I guess it was enough to restrict the flow so that that the burner under the igniter wasn't getting enough gas. I took the opportunity to blow some soot and dust out of the burner array while I was at it. I'm expecting it to work tonight! Thanks for the help!