I turned the heater thermostat to the highest and the fan and gas will come on. About 1 minute later, the gas will go off and the fan will continue another 5 minutes. I might do this cycle one more time and then nothing goes on. \r\n can move the thermostat to cold then hot and it will go through the same drill. Blows cold air mostly.

no the defrost thermostat only need be checked at cold temp and at room or reg temp it should not show any continuity have u checks ur heating element out as well and defrost timer ? I still suspect a faulty thermistor the freezer has more than one thermistor?

Check for error codes and service manual on following link:
http://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html#intellivent

Replace gas control valve
http://waterheatertimer.org/How-to-replace-Honeywell-gas-control-valve.html

Gene:

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If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

Roger, you either have a gas supply issue or a voltage problem.
Since I don't know your aptitude and abilities pertaining to LP gas troubleshooting/testing procedures, I don't know how detailed you want to go...basically, make sure your propane tank isn't empty; or that the pressure regulator didn't freeze up. Make sure that it is rated and set for 28" of water column output.
Check to make sure all the wire connections are secure to the flame control terminal block and to each of the hi-limit switches.
Isolate & perform continuity checks to each electrical component, including the gas valve.
You'll need a manometer to test and set the gas input & output water column levels.

When the unit is running,, what color is the flame?
Is there a roaring sound?
Is the flame small and weak?

Quick call the installer to see if it is still under warranty. There is something wrong if the motor is being replaced every other year. Most of the motors should be lubed with fan turbine oil and not 3 in 1, nor detergent containing oils. If the wrong oil is used, the bearings will go south in 1 to 2 years.

The gas valve is not lifting hence no gas flow , check pressure switch if fitted jump out thermostat see if it lights ,

What about thermostat wire? What ya got 2 wires right? Touch them together she supposed to ignite the flames then after a few minutes the fan kicks in on fan models. You got the knob on the gas valve turned to the "ON" position?

If you need further help, reach me via phone at https://www.6ya.com/expert/dan_73bbd84fe1d95b61

I've got an easy way for you to check, and then we can help you from there.
First pop open both lids to your furnace (this may require a screwdriver). Turn up your thermostat, push the safety interlock button in if it has one (it's a button that turns off the power when the doors are removed), and watch.

On most modern furnaces (past 20-25 years) you'll hear/see:
1. Inducer fan
2. orange glow (ignitor)
3. Gas valve opening and ignition (flames)
4. Main Fan.

that's normal heater operation.
The most common issue here is a burned out ignitor, in which case you wouldn't see the orange glow but the sequence would attempt to continue anyway (the gas valve will open and hiss gas, but it won't lite, then it'll give up and try again a few minutes later).

On older furnaces there's a pilot light to start with, the click of the gas valve and boom... ignition.

On new furnaces it's
Inducer fan
gas valve opening
spark - ignition
Main fan.

and there are some oddballs in between, particularly the Lennox Pulse. If that's your furnace just back away slowly and call a professional... some guys won't even touch those, so be sure to mention what it is... if you call a pro.

So go ahead and watch it run, then tell me/us what you see.

It sounds to me like your thermostat may be bad. I would check power incoming to t-stat then turn temp. setting up and down to see if it is switching on and off. If not then replace. If it does then I would check all wiring to gas valve and if power is shutting off to valve but burner continues then replace gas valve. Thank you.

Do you have an external Thermostat mounted
nearby? It could be that it is to close to the heater and the thermostat is causing it to short cycle

One of the internal safeties are opening causing the main burner to shut down. Ensure you have proper water flow through the unit. It may be a high limit tripping and can be caused by several things, one being the limit is weak, second the heat exchanger may be partially plugged from scale. You may be able to determine the cause if your mechanically inclined, but I would recommend professional service.