All of the sudden tonight it was getting hot went to adjust thermostat and it was blank. No air and no fan. Bought new thermostat (above). checked circuit breakers. thermostat shows it is on but wont kick on. house is 10 years old. while doing wiring it sounded like the air was trying to pop on and off

Can you tell if it is really getting HOT? Perhaps it is just a bad reading that maybe the new sensor will correct? That fits with the delayed thermostat & fans. Perhaps checking with a non contact thermometer?
The compression sounds good so the head gasket must be intact. No mousse on the oil cap or evidence of oil/coolant exchange?
Radiators can get clogged - more use for that non contact thermometer - make sure the radiator has no cold spots indicating blockages.

Sounds like you may have a head gasket leak. But first I would check the water level and get the air out of the system. Air is bad is water system. When bleeding the air squeeze the hoses to burp the air out and I also would suggest looking for a purge nut on the top of a water line or housing on the engine. Check the fan is working or works. And then maybe consider the thermostat was installed wrong.

change the thermostat again , at a different shop . make sure the rad fans are coming on and make sure your water pump is working properly

If the thermostat has a blinking snowflake then it is in time delay mode which sometime can take between 5 to 7 minutes before it will turn the AC and Fan On......Then it will go to a solid snowflake.
When you turned it to fan On it starts the Fan right away..... After the snow flake has went to solid check to see if the fan is running and then look outside to see if the Fan Blade is turning on the AC..... The fan blade comes on the same time as the compressor does. Then with the fan running hold your hand above the air stream above the AC and if you can noticeablely feel warm to hot air comeing out the Top then the compressor is running also. If the outside unit is not running I would check to make sure the Main Breakers are turned ON.... After the AC has ran for a few minutes feel the copper lines that go into the house the smaller line should feel warm to hot and the bigger lines with insulation on it should feel cool to cold and sweating with beads of moisture on it..... That is a quick test to see if the unit is working properly.....If you have a Thermentor and can Check the Temperature of the Return Air and the Supply Air .. You should have about 20 Degree F Between the Supply and Return........ 75* Return - 55* Supply would Equal 20* TD Across the Coil......
That is about all you can do to check on your own....... If the compressor is not coming on or the lines are not the temperature difference then you will need to get professional help for your Air Conditioning System..... Goood Luck Hope this Helps.........

cold air from the fan forced element area in the oven? or from the air vent just above the door? if its from the air vent then this is normal if your oven senses the outside cabinet is getting to hot it will bring on the fan and if its still to hot after u turn it off the fan will continue as its circuit doesnt run through the control knobbs meaning it wont turn off with the oven its controlled via a overload thermostat so the fan will remain on til it gets within its acceptable temp range and the thermostat will cut power to the fan, if it remains on for hours and hours or even days you will be looking at a new thermostat (cheap as dirt like only a few bucks) or worst case a controller

Check the cooling system for leaks...when the heat goes cold like yours did it usually is caused by the coolant level being so far below normal that it won't flow through the heater core. A blown head gasket can also drive coolant out of the system but I's check for leaks first as that is most common. You also need to make sure the fans are operating correctly.
You should change the thermostat after any overheat, as once they are run hot they become unreliable. Since manufacturers have started playing a new game of "hide the stuff you need to work on" It might not be at the engine end of the upper hose where it always was. Take a peek at a chiltons or haynes manual and you can find out where yours is.

it could just be the presure switch try bridging it out and see if burner lights

Best solution GET RID IT BEFORE IT'S TOO LATE....Original 9420 installed 8-18-06 changed temperature by itself and would not allow any adjustments...this one replaced on 1-3-08 and this one is doing same thing. Heat set on 70 when I noticed it getting extremely hot I checked thermostat and it was on 99 and would not allow me to adjust. Switched to off position waited 25 minutes and cut back on to heat....still will not allow me to adjust down from 99.....THIS PIECE OF **** WILL BE REPLACED TOMORROW WITH ANOTHER TYPE OF THERMOSTAT.

First when vehicle is cold like in the morning check and make sure that the vehicle has enough coolant/ antifreeze in radiator and reservoir. If coolant is need use a 50/50 mixture of water and antifreeze. You will need some time to do this let car run at idle until the temp guage is in the middle NOT+ normal operating temperature. At this point if the thermostat should be in the open position. Let vehicle run and check to make sure that radiator fan comes on. This should come on when guage is about midway/half way. If temperature rises above half going to h/hot and fan doesn't come on, you either have a BAD FAN BAD FAN SWITCH BAD FAN RELAY OR BLOWN FAN SWITCH FUSE. You will need to check all of the following I will help if its needed. If fan comes on and doesn't go off and vehicle continues to get hot even with fan running. Feel radiator hoses and see if the lower radiator hose is cool/cold. If it is you have thermostat that stuck closed. Replace thermostat and fix problem. If all the above is good and vehicle continues to over heat. THE BAD NEW IS THAT YOU MAY HAVE A BLOWN HEAD GASKET /CRACKED HEAD /BROKEN WATER JACKET. Basically you will need a HEAD JOB at least a head gasket. ONe tell tail sign of this is oil looking like milkshake/chocolate milk-a creamish while residue in oil or antifreeze. Contact if you need hel0p. Good Luck and thanks for using FIX YA

Check the sensing end of the thermostat. Or check that the thermostat is sensing by checking the m/v output.