Thermostat Replacement

Could be the thermostat, here is guide to help walk you through the replacement with instructions in the diagrams below to show you how on your car.

https://www.2carpros.com/articles/replace-thermostat

Check out the diagrams (Below). Please let us know if you need anything else to get the problem fixed.

With the engine at full operating temp, locate the 2 heater hoses where they go into the firewall and feel them to see if they are both hot to the touch. If not too hot to hold, then you have to look at the actual engine temp and if that is up, if it is, then your looking at a restricted heater core.
If you find that they are both too hot to hold, then the heat in that vehicle is controlled by a blend door that regulates heated air flow. It is operated by an electric motor/actuator. The problem can be that the actuator is stripped or inoperative or the door itself could be damaged. This is what needs to be determined by examining the actuator and see if it is responding to heat change commands or not.
If they are both not too hot to hold on to, then you either have a restricted heater core or the system is not completely full and getting air pockets for some reason.

If you follow the upper radiator hose to the engine, it will lead you to the t-stat housing. Under the housing is the t-stat.

Let me know if you have other questions.

Joe

Yes, it sounds like the problem. The t-stat is located under the water outlet housing on the block. The water outlet housing is the thing that the upper radiator hose connects to from the radiator. There are two types of bolts that hold this to the block. One is a stud and one is a regular bolt. The stud has a nut on it that also acts as an electrical ground. It is very important that you remember to put this ground wire back on after you replace the t-stat. You must drain enough coolant out of the engine to get the coolant level down below the level of this coolant housing. There is no gasket for this housing but I always put a little bead of GRAY silicone on the outter edge of this housing before I bolt ot back on. If you do this, be sure to use only a little bead. The torque on this housing is only 20flbs, do not over-tighten it. Good luck and let me know how you make out.

Hello and thanks for donating

If your temperature gauge is flucuating from cold to hot then back to cold it is probably not an accurate reading. This would be caused by a faulty engine coolant temp. Sensor. For the A/C issue, make certain the coolant level is full.