I have a Ruud Achiever 90 Plus Gas Furnace with Air Conditioner. I have a new Nest Thermostat. What is the correct wiring connections on the Furnace?

be sure the heat anticipater setting on thermosta matches gas valve.

Generally Ruud uses that for a common

I would try to check your return air first, making sure there is no blockage and that your air filters are clean. It almost sounds like when you take the cover off, you are pulling enough air into the system for it to run, but as soon as you close it off, it's not getting enough air flow, therefore, tripping a limit switch inside the furnace. Most furnaces will also have the codes for the flashing lights and what they mean on the inside of the door covers.

Sounds like it could be a dirty or bad flame sensor.
When the burner lights ,there is a flame sensor in the flame and it is suppose to sense the flame and send a signal back to the control board which will keep the gas valve open, if it gets dirty or is bad it doesn't send the signal back to the board and the board will shut the gas valve off and after three tries it will lock out the furnace and you have to reset it to get it to work again.
The flame sensor looks like a wire and it's in the flame usually it will get gas deposits on it, then it won't work.
You can clean this sensor with an extra fine piece of steel wool, but before you attempt to do this DISCONNECT ALL POWER TO THE FURNACE.

Look on the condensor, (outdoor unit) at the very bottom of the rear panel and you should find a red reset button. push it. If that does not solve the problem, and the outdoor unit is running (make sure both the fan AND the compressor are running) then you are looking at a low refridgerant issue and possibly dirty coils.

In that case, clean the coils and have refridgerant added.

sounds like you have a heat pump heat pumps dont work below 30* temps you should have some type of backup heat

Check the data information on the unit there should be a troubleshooting guide that tells you what the two lights blinking once means. hope this helps.good luck. normally found with schematic

the fuse that your refering to is on the control board indie of the furnace. shjould be a 3 amp. good luck.

does the furnace ignite?? your system may not have been lighting and has gone into ignition lockout count the codes of the led lights then remove panel led diagnostic codes are listed there.
if led codes indicate no problem verify capacitor is good and that mtr is getting 115 volts.

The door, you mean the metal cover on the front? if you have the door off and push the safety switch in with your hand everything works fine? I need more info here, but if what I said is right, then the "door" isn't making good contact with the switch.