Astoria Mechanic | Collision Repair | Tolimas Auto Center

Car Overheats when AC is on

Car Overheats When The Air Conditioner is On

As the weather warms up and people use their air conditioners more there are some cars overheat only when the air conditioner is on. This is a common issue on some older cars. This puts the driver in a difficult situation on particularly hot days. Does the driver risk overheating their engine or do they risk overheating themselves and their passengers? The most common reason for this condition is caused by the radiator fans not switching to high speed mode.

When you use your air conditioner all the heat that is displaced by cold, air conditioned air in your cabin is sent to the condenser which is sandwiched between your engine radiator and cooling fans. When you turn your air conditioner on, the fans receive a signal from the computer to spin at max speed. This allows the fans to pull heat out of the air conditioning system’s condenser which will immediately start to get very hot when you run your air conditioner. If there is something wrong with the fans which doesn’t allow them to spin at max speed the heat from the condenser will be absorbed by the radiator which will add heat to your coolant and overheat your engine.

If your car is experiencing this overheating issue

You can easily confirm if your overheating issue is due to a problem with your fans. With your engine running and the A/C turned off observe the fans. They should be spinning slowly or not spinning at all. Then go inside your car and turn the air conditioner on. Once your vents start blowing cold air go look at your fans. They should be spinning at max speed. If they aren’t and your car is overheating then you know the issue is caused by your fans. Any time your air conditioner is on the computer will command your fans to spin at max speed. There can be multiple causes for this. One reason could be the fan motors could be worn due to age. A second reason could be a broken wire that sends the signal for the fans to spin on max speed, needs to be found and repaired. Third reason could be a sticking or damaged fan relay. There are a few other causes for this, that require further diagnosis and might best be handled by a trusted mechanic shop.

If your car is overheating it is best to have the problem solved right away. Overheating your engine can cause mechanical damage to the engine or crack the plastic components of your engine cooling system. If either of these things happen the repairs can be quite expensive. If you need help diagnosing an overheating issue we welcome you to contact us at Tolima’s Auto Center.

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