Good morning:
We have a 1999 Frigidaire LP gas front load dryer (model# FSG748GFS1) which started shutting off after 20--30 minutes. We can not get it to restart until it cools down for up to 30 minutes. After consulting with local appliance store, I replaced the motor ($124). Problem has not changed. Still shuts down with no restart.

Gas solenoids are not reading within the ranges, however, the guy at appliance store didn't think that was problem. See attachment for solenoid readings.

Any thoughts?

Most common problem is from plugged vent or vent fan motor. Make sure air flow is adequate or it will always overheat and trip the safety.

I cleaned the vent out when I changed the motor. Also, the vent is only 8" long straight through wall with no elbows. Great airflow.

Thanks

It sounds like the drier has hardened on deposits which requires it to be disassembled and scraped out then washed out to remove all deposits. You also have a t-stat that regulates the gas valve and a high limit switch which is set at a higher temp. If the high limit switch opens too soon it is usually because of deposits, but occasionally the limit is bad or the t-stat is not opening to regulate the temp. These are cheap and if the drier is very old I would just replace them. DrTom4444

Thanks for the input. Where would the hardend deposits be? Inside the vent tubing? Burner?.
Also, the gas solinoid readings are not within the ranges (+-). Would this be a part of the problem?
Thanks

You will find these deposits anywhere air flows. You disassemble the drier and clean out each piece to remove. They will cause a fire which is why the safeties shut the drier off. Most of the time you can fill a five-gallon bucket about 3/4 full with the deposits you remove. Vacuuming will not remove the deposits. Wash the parts out until clean. DrTom4444