Ford heater blows heat then goes cold temp goes up rev enginge gage goes down

Sounds like the wrong thermostat. It's not opening and closing correctly.

Your temp sensor has nothing to do with your heater. The temp sensor needs coolant in order to work properly. So first check the coolant level because if it is low your heater will act the way you describe. Once the coolant gets low enough the heater will blow cold. Another possibility is the radiator cap. After the engine has warmed up it expands when it cools down it contracts. As it is contracting if the cap is weak air can be drawn into the system and cause air pockets to form and will cause the same problem

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These details will help.
Thanks.

Your radiator cooling fan will only come on when the engine temp has reached the point where it needs to have air forced through the radiator and thus bring engine heat back down to safe operating range. If your heater is not working check to make sure the fresh air vents aren't stuck open (are the controls stiff or not going all the way across?) check also that the heater shutoff valve lever which is usually situated on the firewall at the rear of the engine and can be found easily by tracing the hoses back from the thermostat housing aren't bent and/or seized up.

Could be a plugged heater core, or bad water pump.

jtg

first check to see that you coolant level is full, check it after the engine has cooled down,so there is no pressure in the system. otherwise you possibly have a head gasket in the early stage of failure

sounds pretty normal. its not overheating but if you still want to do anything try replacing the thermostat and see it it changes

Just finished fixing my daughters 1999 taurus heat. It would blow warm only when running down the road. At idle it blew cold. I started with replacing thermostat, and water pump because they are the easier fix. Still did not help. Then I replaced the heater core. A daunting job but not that hard to move the dash slighly out of the way to replace. There is a good write up at tarusclub.com. After that, heat was better but at idle, it would still blow cool sometimes. Researched and found answer. Park car on the steepest hill you can find with front of car up. Start car and take off reservoir cap. Let car warm up and keep rpms about 1500. After a while the fluid will come running out of the car and all over the place but it will bring air bubbles with it. Reduce rpm, add more fluid and repeat about 3 times. It will make a mess but after that, the heater works perfectly. We get heat long before the temp gage indicates any and it never blows cold unless you lower the temp.

start you truck. let the temp gage get to where it will start blowing the antifreeze out. than turn your heater on full blast. if the temp goes down and the water doesn't come out than you need to change you thermostate.