Are you in a situation where your car’s air conditioning is blowing cold air, yet your engine refuses to start? It’s a frustrating scenario to encounter, leaving you puzzled and stranded.
In this guide, I’ll delve into the confusing scenario of why your car might fail to start but the ac works.
Here’s why your car won’t start but the AC works:
1. The battery has problems
The battery is the primary source of electrical power in your car. It provides the necessary power to start the engine by cranking it.
When the battery is weak or depleted, it might not have enough power to turn the engine over, resulting in the car’s inability to start.
The air conditioning system typically requires less power compared to starting the engine. As a result, even if the battery lacks sufficient power to start the engine, it might still have enough charge to operate the AC.
Common symptoms:
- Slow engine crank or no crank.
- Dimming lights.
- Clicking sound.
- Check for warning lights on the dashboard, such as the battery or check engine light.
- Electrical Malfunctions such as issues with power windows, door locks, or radio functioning erratically.
Related: Car won’t start but radio works (Explained)
Solution:
Use a multimeter to check the battery’s voltage. A fully charged battery typically measures around 12.6 volts. Anything significantly lower might indicate a weak or discharged battery.
If the battery is low, try jump-starting the car using jumper cables connected to another vehicle or use a battery charger to recharge it.
If the battery is old, weak, or unable to hold a charge, it requires replacing it with a new one.
Regular maintenance and periodic checks of the battery can prevent this issue. This ensures the battery terminals are clean, free from corrosion, and securely connected.
Also, have your car inspected by a professional mechanic if you detect any of these signs and why your car won’t start but the AC works.
2. The starter motor has a problem
The starter motor is responsible for initiating the engine’s operation by turning the crankshaft. If the starter motor malfunctions or fails, it won’t be able to turn the engine over, resulting in the car’s inability to start.
The air conditioning system operates independently of the engine starting. It relies on electrical power from the battery to function, which means even if the starter motor fails, the AC might still work as long as the battery has enough power.
Common symptoms:
- A clicking noise when turning the key in the ignition, without the engine cranking. This clicking noise usually indicates that the starter solenoid is engaging but not successfully turning the engine.
- Instead of the typical cranking sound, you might hear a freewheeling or whirring noise when attempting to start the engine. This noise signifies a problem with the starter motor’s gear engaging the flywheel.
- No response when turning the key
- In severe cases of starter motor malfunction, you might notice smoke or detect a burning smell under the hood, indicating an overheating or electrical issue.
Solution:
Diagnosing and repairing starter motor problems often require the expertise of a professional mechanic.
A mechanic is required to perform diagnostic tests to determine if the starter motor is the culprit by checking the electrical connections, solenoid function, and motor operation.
If the starter motor is confirmed to be faulty, it will need to be replaced.
3. You have ignition system failure
A car that won’t start but the AC works can be caused by ignition system failure.
The ignition system is responsible for creating the spark that ignites the air-fuel mixture in the engine’s cylinders. If any component within the ignition system fails, it can prevent the spark necessary for the engine to start.
The operation of the air conditioning system is independent of the ignition system. As long as the battery has enough power to run accessories like the AC, it may still function even if the ignition system fails to start the engine.
Common symptoms:
- The engine cranks but doesn’t start.
- No spark or weak spark when sing a spark tester or diagnostic tools to check for the presence of a spark at the spark plugs.
- An ignition system problem might cause the engine to run rough, misfire, or experience poor performance when it does start.
- The check engine light might illuminate due to ignition-related issues. This light serves as an indicator that the engine’s computer has detected a fault, including potential wiring or connection issues.
Solution:
A mechanic can perform tests to check various components of the ignition system, including the spark plugs, ignition coils, distributor (if applicable), ignition module, and ignition switch, to identify the specific faulty part.
Depending on the diagnosed issue, components of the ignition system that are malfunctioning may need to be replaced.
This could include replacing spark plugs, ignition coils, or other related parts.
Related: My car starts after jump but won’t start again new battery (Here’s why)
4. There could be fuel delivery issues
Fuel delivery issues can prevent the engine from receiving the necessary fuel for combustion. Without adequate fuel, the engine won’t start, even if the AC system operates normally.
The air conditioning system uses a separate circuit and does not rely directly on the engine’s combustion process.
Therefore, if there’s enough battery power to run accessories like the AC, it may function despite fuel delivery problems preventing the engine from starting.
Common symptoms:
- Cranking without starting.
- Engine sputtering or stalling.
- Difficulty starting when cold.
- Low fuel pressure.
- The check engine light might illuminate due to fuel system-related issues, indicating faults with components such as the fuel pump, fuel injectors, or fuel pressure sensor.
Solution:
Seek help from a certified mechanic or auto electrician to conduct tests to inspect various components of the fuel system, including the fuel pump, fuel filter, fuel injectors, fuel lines, and pressure regulators, to identify the cause of insufficient fuel delivery.
Faulty components within the fuel system, such as a failing fuel pump, clogged fuel filter, or malfunctioning fuel injectors, need to be replaced to restore proper fuel delivery.
Regular maintenance, including fuel filter replacement as per the manufacturer’s recommended intervals, and using quality fuel can help prevent fuel delivery issues.
Also, keeping the fuel tank above a quarter full can prevent strain on the fuel pump and fuel system components.
5. The engine sensors or computer have problems
Engine sensors gather data about various parameters (such as temperature, airflow, crankshaft position, etc.), sending signals to the car’s computer, known as the Engine Control Module (ECM) or Powertrain Control Module (PCM).
The computer uses this information to control various engine functions, including fuel injection, ignition timing, and more.
Malfunctioning sensors or computer issues can disrupt these critical functions, leading to starting problems.
The operation of the air conditioning system is not directly linked to the engine control system.
So, if there’s an issue with engine sensors or the computer system preventing the engine from starting, the AC might still function if other electrical systems are operational.
Common symptoms:
- Illumination of the check engine light on the dashboard which signifies that the ECM or PCM has detected a problem and logged an error code.
- Engine stalling or Rough running, stalling, or hesitation during acceleration.
- Problems with engine sensors or the computer system can negatively impact the engine’s performance, resulting in reduced power output or decreased fuel efficiency.
- Faulty sensors or computer issues might cause difficulty starting the engine or extended cranking times before the engine starts.
Solution:
Seek help from a mechanic. They can perform diagnostic tests to retrieve error codes stored in the vehicle’s computer system.
These codes can provide valuable information about which sensors or systems are experiencing problems.
Faulty sensors identified through diagnostics require replacement to restore proper operation.
Related: My car won’t start after jumping another car (Here’s why)
6. Security system activation
Many vehicles have immobilizer systems that can prevent the engine from starting if an unauthorized key or key fob is used, or if the system detects a potential security threat.
This security feature might interrupt the engine starting process, even if other electrical systems like the AC continue to function.
The air conditioning system is not directly linked to the vehicle’s security system. Therefore, if the security system inhibits engine starting due to a perceived security threat, the AC might still operate as long as the system recognizes the key or key fob used to access the vehicle.
Common symptoms:
- The engine cranks but doesn’t start.
- Flashing or solid security light.
- Key fob malfunction such as a low battery or damaged transponder chip, might trigger the security system, preventing the engine from starting.
Solution:
Ensure the key fob has a good battery and is functioning correctly because a malfunctioning key fob can trigger the security system.
Try locking and unlocking the vehicle using the key fob or key in the driver’s door to reset the security system.
In some cases, a security system reset might be necessary. This involves disconnecting the car’s battery for a few minutes or using a manufacturer-specific reset procedure.
7. Wiring or connection issues
A car that won’t start but the AC works can be caused by wiring or connection issues.
The wiring in a vehicle carries electrical signals to various components, including those involved in starting the engine.
If there’s damage, corrosion, loose connections, or a short circuit in the wiring, it can disrupt the flow of electricity needed for engine starting, while allowing other systems like the AC to function.
The air conditioning system has its separate wiring and circuitry. If there’s a problem in the wiring or connections specific to the engine’s starting process, it won’t necessarily affect the AC’s operation as long as its electrical circuit remains intact.
Common symptoms:
- When attempting to start the engine, there might be no power to the starter motor, or the engine doesn’t crank at all.
- Occasional issues such as sporadic power loss to certain components, flickering lights, or accessories intermittently working and then suddenly failing.
- Visible signs of corrosion, fraying, or damage to wiring harnesses, connectors, or terminals under the hood or within the electrical system.
- Failure of certain electrical components or systems that are crucial for engine starting, such as the ignition system, fuel pump, or starter motor, can also be indicative of underlying wiring or connection issues.
Solution:
Seek help from a mechanic to perform a professional diagnostic check of the wiring harnesses, connectors, and terminals for signs of damage, corrosion, or loose connections to help identify potential issues.
Repairing damaged wiring, cleaning corroded connections, securing loose connections, or replacing faulty wiring harnesses or connectors is necessary to resolve the problem.