Heater shutting down and needs reset to turn back on

Things to do/check first....

Insufficient airflow *WILL* shut the system down.

I have a heater that when turned on works for a while, sometimes getting up to temp in all zones sometimes not then turns off and needs to be switched off for 10 min or so before being switched back on and working (for a while) again. Last summer I had the same problem with the AC, working for a while then turning off needing a hard off/on to work again. Had a tech come look at it but once he took off the cover to the system it reset and worked. He called it good and charged me but an hour or so later it shut itself off again. Can anyone give me an idea as to what this might be so I am armed with a little understanding when I get the next tech out to work on it. Thanks

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Sounds like the cover is on too tight. Try taking the cover off again.

"A heater".

Excellent, that really narrows it down.....

Pretty much rules out the refrigerator, anyway.....