Thermal cut off fuse keeps shutting down heat in dryer housing

Dryer Repair
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1

Brand:Kenmore Series 90
Model Number:110.66902692
Main Symptom: no heat
What happens & when:5 minutes after drier starts, heating element shuts off

Error Code (if any):
Parts or tests already tried: replaced thermal cut off switch, thermal fuse, cycling thermostat, new timer, new control board, new temp selector and a brand new motor and belt plus three heating elements. This began about 2 months ago, i notice my clothes taking longer and longer to dry. Even though I tested everything with a multimeter, the elements, fuses were all good except of course the thermal cut off. The only thing I noticed from installing 3 heating elements all new (and they are all good) is that the heating element only illuminates and turns red halfway, the front of the element doesnt turn on it seems, therefore the thermal cut off shuts down because it is at the back of the housing. I tested the housing of the element as it is not grounding the element. I checked all the wires on the housing, terminals all good, no melted, frayed wires, all pristine. Someone mentioned to look at the terminal block behind the drier (which I havent done yet) that the voltage seems to be working halfway. I had tested the 240 outlet on the wall, tested fine too (I think) only tested a few seconds each live section of the 3-prong. No blockages, the drier is lint free everywhere. The drier works smoothly except for the heat. Had it for 25 years and replace many components I didnt have too, but now clueless.
Photos / video link:

2

Does the dryer keep running but just not cycle the heat correctly? If your dryer is near a window, try disconnecting the vent hose from the wall and aiming it outside. If you don’t have a window nearby, just remove the vent from the back of the dryer. Start a timed dry cycle. Does the element still fail to cycle?

3

Yes, the dryer keeps running, zero heat after 5 minutes, the element only heats halfway and then shuts off. Just curious as to why the vent must be removed, it is clear (I checked) and the blower is strong. Just wondering because I have to remove the element and replace the thermal cut-off switch since it is blown again.I do have spares, but, still, I have get down and do it.

4

Taking the vent off helps confirm if it’s really an airflow issue, since running it without the vent rules out any blockages in the house duct. If the thermal cut-off has failed multiple times, what voltage do you get at the terminal block when you test from the red wire to the black wire with your meter probes?

5

Thanx for the clarification. I’m working on it now, you know, I don’t even have a terminal block, the wires from the cord go up directly into the timer. I put a new timer in thinking it would solve the problem about a month ago, did nothing at all. I’ll test the red and black wires and get back shortly.