Why Do Overheat When You Go Uphill With The A/C On?

Your AC works by a belt coming off the engine, so when it is on, it takes more power to do, causing more heat in the engine. Also you are going slower, so you get less airflow, which in turn is more heat.

Even your auxiliary fans cant keep some cars cool enough, so they dont want engine overheating on the side of a mountain, that is no good.

The use of AC does not take power away from the "engine fan" or the cooling system. The cooling system works whether you are driving on a flat highway or a mountain highway. But as simple as that sounds it is still a very complex system. And a very well designed system.

The cooling system is just that... it keeps the motor cool. It consists of several components, such as the radiator, water pump, fan/fan clutch, belts, thermostats, overflow bottle, coolant and more. All of these things working together will keep your vehicle running cool and efficient.

But now you turned on the AC...! What is going to happen now?

Basically speaking, the AC is like the refrigerator in your kitchen. It is another vehicle system that requires power to operate. In your home, the refrigerator is usually on a different circuit because of the amount of power it uses. If it wasn't on a different circuit you would have blown fuses or tripped circuit breakers.

In a vehicle, the AC needs to share the power source with the rest of the vehicles systems. The AC id powered by an AC belt. This AC belt is driven by the same power source that keeps the motor cool. So, when you are climbing a steep mountain pass the cooling system is already working hard. But when you turn on the AC you are adding additional mechanical components to the engines work load. This will cause a couple things to happen.

1. Your engine will lose power

2. Your engine will run hotter

If you have a good running vehicle you should have no problem making it up the mountain passes with your AC blowing at full speed. Even if you are driving very slow. The vehicle manufactures have already taken that into consideration.

But the Dept. of Transportation knows that not everyone has an efficient and properly running vehicle. So they post a "blanket" warning to all drivers to turn off the AC.

If you are concerned about your vehicles cooling abilities you should have the car checked out. A vehicle that doesn't keep cool can cost you some serious $$$ problems if it overheats. Especially cars that are less then 25 years old as most vehicles have cylinder heads that are made of alloys. (But that is another story all together...)

If you have no reason to believe your car is not working well, leave the AC on. Monitor the temperature gauge. It will go up slightly. Not a big deal! Just make sure that it does no go into the "red zone". If you are worried, turn off the AC. But still, always monitor the temperature gauge.

If you're driving up a steep highway and your car is starting to overheat then pull over to a safe spot AWAY from the roadway! Open the hood and leave the motor running and monitor the temperature gauge. You want to keep the water/coolant circulating throughout the motor. If the car continues to get hotter you may be forced to stop the motor.

NEVER OPEN THE RADIATOR CAP or COOLANT BOTTLE

I hope this helps.

When you go up hill you are in heavy gears i.e 1,2 or so. These gears needs more power as compared with light gears 4,5. A.C loads the engine another time. The total required power load of heavy gears plus AC load results the engine heating up.

Following tips are suggested for you,

1-You can minimize the heating factor by adding a quality engine oil

2- Good collent to your radiator.

3- Cleaning air filter with air pressure gun or replacing it with a new one can give much better results.

Cause youre engines having to work harder with the A/C on. Also the air is more dense.

Motor working much harder. Working hard makes heat. Sometimes radiator can't process more heat.

less air going in