The length of duct in the wall and up to the roof hood must also be checked for obstruction.

Gas dryers can suffer failing solenoids on the gas valve ... they may test good when the machine has sat idle for a while but fail or become erratic under operation. It's a simple fix but replacement parts for some older models have gone NLA. You didn't cite the model of your machine for anyone to check on it. A skilled/competent servicer can sometimes find a substitute but good luck on that.

The serial number is coded for the date of manufacture, year & week or year & month depending on which of Sears' suppliers manufactured it.

the model number is 110.77741600 if that helps. Thanks. I was looking online as washers and dryers and got overwhelmed. Putting a call into the appliance repair company to check it out.

The valve solenoid/coil kit is available if that is the problem, P/N 279834. An online source I frequently use lists it at $13.82. A servicer will of course charge trip/diagnosis, their retail on the parts, repair labor, sales tax, perhaps a return trip if they don't stock the kit and must order it and return to finish.

This repair company I've used has always had the part with them them need. (fingers crossed) They wont be able to get out till next Tuesday though.

It was the vent. Needed to be cleaned. Luckily I was able to get someone out the same day and the dryer is heating up perfect.