Goodman GMNT100-4 condensing gas furnace installed in 2002 uses propane gas.
Motor turns on at thermostat setting but no heat. I have only the installation & Operating manual but see no pics of what/how to troubleshoot. Have taken front panel off and see no sign of ignition nor odor of gas.
Any thoughts - Thanks.

It could be many different things.

First turn off main power at panel and after a few seconds turn back on. This will cause a reset. Then go to the furnace and see if it runs. Post back with results

Thanks for help, did that and no difference at all. Got call back from service firm and they s/b here today.

Problem was igniter - I can see burn marks. NOW, part # B1401015 no longer seems to be produced & I'm told I'll need to retro fit a universal igniter. It seems to me that if Goodman no longer makes this part # there should be another after market mfgr who makes a part I do not need to modify.

Any thoughts?

Yes since the part is no longer available it has been substituted with a newer and better part more than likely. You will need to buy the change over part and install it if you want your unit to operate. Parts become obsolete every day in the HVAC industry just be glad you do not have to replace the 200.00 circuit board to go with the new ignitor. The new ignitor might need modifications to fit your furnace but that can only be told once the new part is obtained and the install is done.

Furnace Ignitors/Pilot Assy

Thanks, I'll have the answer tomorrow.