1. low gas pressure 2. weak ignitor 3. debris blocking burner closest to the ignitor Gas is actually filling the chamber but missing the ignitor in most cases. When it hits the top and mushrooms down, BANG! Very typical for this heater.

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.

I have not used my heater for about a year. I installed new propane. I only get a power led. When I switch the rocker switch to pool or spa nothing is happening. Had a tech come check it out and he said it needed a new circuit board. He wanted way too much for the board so I bought an OEM on line and installed it. Nothing changed. I can see that the water pressure switch is working. It is 10 years old. Got any ideas?

The original symptom was that there was no information on the DDTC except for a Pressure SW indicator. Replacement of the DDTC module fixed that. What I have found since I posted is that I have only 13.7vac coming off the transformer, with good line voltage going in. It seems that these transformers are fairly standard, so I will be getting one tomorrow. That might explain why my DDTC fried, right? Seems it would be simple to have incorporated a low volt fault system to keep a 5.00 transformer from killing a 300.00 DDTC.