Thanks for the input, everyone. So far, I haven't had any problems with damping off (knock on wood). But maybe I'll open my foam doors during the day when it's warmer, and close them up at night when they could use the extra protection. The picture is a little deceiving in that it makes the top look more "closed" than it is. But I'd hate to lose 14 tomato seedlings that are doing beautifully at the moment. Larry, my set-up is out in my garden shed, unheated, which is why I wanted to add a little insulation. This seems to be working good. And yes, it was refreshing building something with duct tape! LOL My first idea had been to make a box out of some scrap wood I've got, then cover it with foil. When I saw that the 4X8 sheet of foam insulation was only $8 I decided I could "splurge". It was worth it!

Let's assume there is air in the line if the gas was off for any period of time. The heater will lock out after three tries to ignite. Each time it tries to ignite, after that click, you will usually hear the gas flowing at the meter. It will flow for 7 seconds and then shut down and retry for a total of 3x. If the gas has not made its way through the pipe in those 3 tries, you will need to turn the power off to the heater and do it again. In most cases, it's about 5 attempts before the average gas line purges the air. The giveaway here is if it is trying to ignite and you don't smell gas blowing out, you have air. The presence of gas with a good igniter will light as long as you have a good igniter and clear burners. The quicker way to bleed the line is to open up the union in the line until you smell gas. Shut it off and then tighten the union.

I did some more troubleshooting of this problem. When attempting to run the heater, I found that the green power light stays lit continuously (as it should), but the display is reading "OFF". After 30 seconds or so, the Pressure Switch green light comes on for only a few seconds. During this brief time, the screen display shows "- - -". Then, the Pressure Switch green light goes out and the screen displays "OFF". After another 30 seconds or so, the Pressure Switch light again turns on, the screen shows "- - -". After a few seconds, the Pressure switch light goes out and the screen again shows "OFF". This process keeps repeating, but there is no error code. Does anyone have an idea about what could be causing this problem or what needs to be fixed? It would be much appreciated.

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!