[COLOR="RoyalBlue"]I checked and cleaned the vent. I have 220volts going to dryer. I have removed the thermostats from the heating element housing, and tested with an OHM meter. The 4 wire one L210-30F 0624 HTR120V6-9T21the outer prongs test no ohms. The inner prongs are open and read continunity.[/COLOR]

An open thermostat will read infinity, or, OL. No current can flow through it.
On a cycling thermostat (four terminals), the smaller terminals go to an internal heating element that is used to accomplish your variations in temperature settings. It will have some resistance, if it isn't broken (open).

[COLOR="RoyalBlue"]The other thermostat is two wire, L210-30F 540B146 this one tests closed no continunity.[/COLOR]

"No continuity" means that it is open, and should be replaced.

[COLOR="RoyalBlue"]What do you suggest I test or do next??[/COLOR]

Recheck, to be sure of the condition of the thermostats. If you're getting SOME heat, you may have one half of the heating element burnt out. This is common with GE dryers.

As for the vent, make sure it is clear from the dryer all the way to the outside of the house. If your vent exits at the side of the house, make wure there are no bird or squirrel nests in it. If it exits through the roof (as in the homes in my area, it wouldn't hurt to have it cleaned professionally every couple of years or so.