Why does my temp gauge get a little higher in the winter, but in the summer its perfectly fine?

Question

I own a 97 Subaru Legacy, and this is mind boggling to me. In the summer, the AC is on and the temp doesn't raise, but in the winter when it's cold, it raises pretty high. I have to turn the heat all the way up to bring the needle down. Someone help!

Answer 1

Now that is interesting. My Escort reaches the same temperature on a frigid winter day as on a hot summer day with a/c on, and it hasn't varied by more than a few degrees maximum for 3 years. If you have a thermostatically controlled radiator cooling fan, the switch may be shot, or the fan itself may be dead. If the temperature is fine when you are cruising the highway in the summer, and creeps up when you are in town, that sounds like the fan is either not coming on, or is coming on really late. That isn't a terribly expensive fix either way.

Answer 2

There's a mechanical thermostat that opens and closes allowing coolant to run from the engine to the radiator and when it is very cold this thermostat may not open at all or not open fully. Sometimes you will se the temp go up and then down and then up and then down over and over again in extreme cold as the thermostat opens and closes. Depending on engine design, some thermostats allow seepage of coolant to the radiator even when closed so that the hot coolant can reach and effectively "open" the thermostat. Otherwise the hot coolant runs past or near the thermostat without passing through to the other side so the thermostat may open at too high a temperature and the rapid change in coolant temperature from boiling hot to ice cold (as in the dead of Winter) causes too rapid a change in engine temperature and this creates stress on the engine management systems and can cause a headgasket problem.

The cold Winter air temp's actually help cool the engine through the air intake manifold, the heater core, and the engine block, in your case I believe it's aluminum, and of course the radiator.

Your cooling fans (radiator fans) will not come on in Winter and may run non-stop in Summer.

The only thing you might check if this bothers you is the actual mixture of coolant and water. It need to be a 50/50 mix and I recommend you use distilled water when you mix it with antifreeze. This keeps scale from building up in the coolant jacket and cylinder heads and radiator. They sell these little antifreeze/water concentration testers in most department and auto parts stores.

If this were an air-cooled engine the opposite would be true and none of the above would apply.

Good Luck!

Answer 3

When you are running the A/C, the electric fan is on all the time. With the A/C off, the fan only runs when the engine reaches a certain temp. My Chevy is the same way.

Answer 4

simply because of your a/c fan and radiator cools the air down before it gets to your motor radiator