Air conditioning not running after disconnecting battery

After I turned off engine, I could hear the air conditioning fan or blower still running. My son disconnected the battery and it stopped. He put it back, but the air conditioning is no longer running.
Experienced mechanics share their insights in answering this question :
The AC in your car is controlled by its own computer. There are 50 wires going to it. For a proper diagnostic a scan tool would be needed to check for codes, in this module, and all the others. It sounds like the computer is malfunctioning. A qualified mechanic from YourMechanic can come out to diagnose your air conditioning system to see where the trouble is.

How to Identify and Fix Common car Problems ?

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If you recently serviced the electrical system and now your AC is no longer working then it may be possible that the issue is related to the work. The first thing I would do is check the vehicle`s fuses and relays. It may be possible that one of the fuses or relays blew when the battery or alternator were disconnected.
Generally no. A battery replacement won`t have any effect on a vehicle AC system.
When your air conditioning system keeps running and never seems to shut off, the problem could be linked to a number of malfunctioning components – frozen evaporator coils, a clogged air filter, a bad electrical relay switch that needs to be replaced, the fan blowing constantly, dirty condenser coils, a bad thermostat, …
Look for it first around on the exterior of your machine, especially along the bottom edge near the ground. An AC`s reset button is typically red and visible, so it should be easy to spot. If you don`t see a reset button on the outside, it could be located inside the unit behind the service panel.
Most air conditioning units are equipped with a reset button. These buttons tend to be red and quite small. If you`re having a tough time finding it, consult your owner`s manual. (If you can`t find it, most are published online for quick reference).
Your air conditioner`s internal circuitry needs some time to reset after you turn it back on. This can take approximately a half-hour, so sit tight for about 30 minutes. Turn your air conditioner back on at the thermostat. After 30 minutes have passed, turn your air conditioner back on at the thermostat.
If your thermostat is programmable, then the problem may lie with the batteries. Dead batteries will prevent the thermostat from sending the startup command to the air conditioner. Fortunately, battery replacement is an easy and cheap fix well within the reach of homeowners.
Just as with your headlights, a failing alternator will cause the failures of other electronics of your car; from power locks to windows, air conditioning, internal lighting, etc., these will operate at a slower speed than average or stop working altogether.
If your thermostat is programmable, then the problem may lie with the batteries. Dead batteries will prevent the thermostat from sending the startup command to the air conditioner. Fortunately, battery replacement is an easy and cheap fix well within the reach of homeowners.
If your air conditioning unit has stopped working, there are many possible reasons that can explain why. It could be your thermostat, your air filter, a problem with the condenser or compressor, or it may just be time to replace the unit, especially if it`s over 10 years old.
The easiest explanation for your AC not turning on is a thermostat problem. Check to ensure your thermostat is on, set to “cool,” and that the temperature is set to a few degrees cooler than the normal ambient temperature of your home. You may also need to replace the batteries.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

Air conditioning not running after disconnecting battery
ANSWER : The AC in your car is controlled by its own computer. There are 50 wires going to it. For a proper diagnostic a scan tool would be needed to check for codes, in this module, and all the others. It sounds like the computer is malfunctioning. A qualified mechanic from YourMechanic can come out to diagnose your air conditioning system to see where the trouble is.

Air conditioning is blowing hot air – car stalls when A/C is on
ANSWER : In order to diagnose all the different problems you have, I having the A/C pressures checked to see if the system is low on refrigerant from a leaking compressor or another component. The rough idle may be due to a dirty throttle body and idle control system. If you would like to have this checked for you, a certified professional from YourMechanic can come to your car’s location to inspect the A/C and rough idle in order to proceed with the proper repairs.

Hot air mixed with cold blows from air conditioning
ANSWER : Hey there. You will most likely have to have a mechanic bypass the heater coolant lines to have this resolved. Your A/C may not be controlling the air flow inside the evaporator correctly out of the vents and may be the blend door actuator stuck in the heat position. Have the AC system diagnosed first before bypassing the heater.

My 2003 Hyundai air conditioning works fine but often starts blowing hot air, especially when idling.
ANSWER : Hi There,
It sounds like you may have a condenser fan that may not be cooling the AC condenser properly. As you may know, the job of the AC condenser fan is to cool down the AC condenser as it generates a lot of heat during the course of its primary function, which is to convert the AC gas refrigerant into a liquid form, a process that generates a significant amount of heat. As the AC condenser fan blows cool air across the condenser, this allows the condenser to remain cool, keeping the pressure down in the AC system which helps to generate cooler air. I would suggest having a professional from YourMechanic come to your location to take a look at your vehicle.

Air conditioning blowing mildly cold air on the coldest setting, turned off/on again, now blowing cold air, should it be checked?
ANSWER : If you are getting ready for a long trip and suspect the cooling fan may be not coming on for the radiator and a/c then you should have the a/c and cooling system performanced checked before trip. Nothing worse than breaking down when out of town in a strange area.

Has new alternator, new battery when started , motor dies when battery is disconnected…my mechanics are stumped on this
ANSWER : Hello.

If replacing those particular components did not correct the issue then the next thing I would look at is the vehicle’s voltage regulator. It appears that this engine’s electrical system is equipped with an external voltage regulator that functions, or malfunctions, independently of the alternator. The voltage regulator regulates power from the vehicle’s alternator, and can cause issues with the electrical system when it malfunctions. I would test it to see if it is functioning properly. It is a silver box that should be mounted somewhere in the engine bay, usually on a wheel well. A technician from YourMechanic can come to your home or office to replace your car’s voltage regulator if necessary.

Regards,
Eduardo

Air conditioning doesn’t work – 1988 Jeep Grand Wagoneer
ANSWER : Check the fuse for the heater/AC blower motor. If the fuse is good, then either the blower motor resistor or the blower motor itself is suspect. The blower motor resistor provides for multiple speeds for the blower motor. A professional mechanic, like YourMechanic, can diagnose and replace the failing component.

Needs jumped to run
ANSWER : Hi there. Yes, it is quite possible that you have a short in the electrical connection from the battery to the alternator or inside the alternator output. This is typically what causes the type of issue you’re describing. In most cases, replacing the alternator and electrical harness from the battery charging relay to the alternator would resolve this. However, it’s also possible that you may have an exposed wire somewhere or loose ground wire as well. This can be a tricky thing to diagnose, so it might be a good idea to have a professional mobile mechanic come to your location to complete a car is hard to start inspection.