Can a Bad Battery Affect Air Conditioning in a Car
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If the radiator fan isn't working, a failed relay is one of the possible causes. The relay isn't the only possible cause, nor is it the most common cause. If your vehicle has two fans and one of the two fans isn't working, the problem could be the bad fan or a faulty relay.
Since engine heat can be so destructive when the vehicle is stationary, an inoperative fan should be dealt with as soon as you know it isn't working. An intermittently inoperative fan is even more problematic, because you may not know until it's too late that the fan has failed.
Bad Cooling Fan Relay Symptoms
The relay is a critical part of the cooling system. When it malfunctions or breaks down, it affects the fan. Keep a lookout for the following bad cooling fan relay symptoms:
The engine runs hot or overheats
Is the engine running hotter than usual at traffic signals and drive-thru lines or parked and running? Watch your gauge! Is it overheating faster and without warning? The issue may stem from a malfunctioning cooling fan relay, wiring, or the fan itself. If the A/C Condenser fan isn't working the A/C may stop cooling when the vehicle is in traffic and the "pop off" valve on the compressor may release the excessive high pressure due to elevated temperatures, making a loud noise and some mist from under the hood.
But again, a bad cooling fan relay isn't the only culprit for excessively high engine temperatures or A/C Condenser overheating. Many other issues can cause these problems.
The cooling fans don't work
Rather than uncommonly high engine temps, the driver may notice that the cooling fans have stopped running. A faulty or broken relay cannot deliver power to the cooling fans. In turn, the unpowered fans won't run, leaving the radiator to its own devices.
Deprived of the helpful influx of air from the cooling fans, the radiator cannot remove as much heat as it usually does. It sends still-hot coolant back to the engine, causing temperatures to rise as the coolant fails to do its job of cooling down the motor.
The cooling fans keep running
Conversely, the cooling fans may keep running even when the engine is offline. This odd behavior indicates a different issue in the relay that controls the fans. A stuck closed relay can cause this, but some vehicles may run the fans by design after the engine has been shut down. The key is whether this has just started happening or if it's a new pattern you've noticed. Normalcy is the key, whether you're listening to the fans, watching your gauges, or anything else. Watch for changes.
An electrical open circuit in the relay coil can allow relay contacts to remain in their open position and never close. A shorted control circuit or stuck relay contacts can continue to deliver power, keeping the fans running continuously.
Obviously, if the fans run all the time, they will drain the battery.
Warning lights
If the cooling fan relay has failed, you may see warnings, such as the check engine light and the temperature warning light, pop up on the dash, but first, you may notice that the A/C stops cooling. More about that in the next paragraph.
Poor air conditioning performance
A faulty cooling fan relay can also negatively affect air conditioning (A/C) performance. The reason being, on most vehicles, is that the cooling fan doubles as a condenser fan. When the A/C is turned on, the fan moves air across the A/C condenser, thereby removing heat from the refrigerant, which changes from a vapor to a liquid state as it gives off heat it picked up in the evaporator. That's why they call that component the "condenser."
Possible Causes of a Bad Cooling Fan Relay
Cooling fan relays can stop working for any number of reasons. Common causes for relays failing to operate might be:
- Failure of the computer, temperature switch, or relay control module that turns the relay on or off.
- Damage caused by changing between circuits with different speeds and electrical load
- Ants in the relays (more common than you'd expect).
- Relay failure due to high current draw from a partially shorted fan motor or intermittently shorted fan circuit.
How to Tell if Cooling Fan Relay is Bad
There are several ways to tell if a bad cooling fan relay is to blame for an overheated engine. You can try the following methods:
Swapping Relays
The easiest method is to start the engine and then turn on the air conditioning. If the fan doesn't engage, there may be something wrong with the cooling fan relay. Of course it may be the fan. One good rule of thumb is that the hardest working component in the most hostile environment is most likely to fail. That's usually the fan itself.
If the cooling fan does not engage, you can check whether the relay is to blame by swapping it out for a different relay. This only works if the fan is driven by a single relay – as stated earlier, many fan systems have a module, or they may have 2 or 3 relays working together.
Many automotive relays are similar in design, so you can simply take a relay from a different, noncritical system and insert it in place of the cooling fan relay. WARNING: On newer cars, this can be dangerous though, so don't swap relays that have different part numbers (usually it'll be on the relay) even if the terminals look the same!
If you have a single fan relay and you can find another relay with the same part number, you'll know the cooling system relay is faulty if the fan works with the substitute relay. A caveat – cooling fans can work intermittently – relays usually either work or they don't.
Measuring the Relay Coil's Resistance
You can also measure the relay coil's resistance. A normal relay's resistance will read between 40 to 80 ohms. Higher resistance levels warn that the coil has started to fail while lower readings mean the relay has broken down.
Listening for Noises
Still another DIY test involves shaking the cooling fan relay and listening for any noises. A broken armature will rattle around the relay.
Thumping or Bumping the Relay
You can also thump or bump the relay to see if the fan kicks on. You can listen to the relay to see if it "clicks" when it is energized, but that doesn't mean the relay is good – it can "click" and still not deliver power to the fan.
What Does a Cooling Fan Relay Do?
The cooling fan relay is an electromagnetic switch that controls the power supply to the engine's cooling fans. It ensures that the energy-intensive devices only run when needed, usually when the vehicle is immobile.
When the engine temperature approaches unsafe levels, the vehicle's computer or temperature switch turns on the cooling fan relay. The activated relay completes a circuit, allowing an electric current to flow through it and reach the cooling fans.
To learn more about how fan relays (and relays, in general) work in the cooling system, read our in-depth explanation here.
Different Types of Cooling Fan Relays
There are several types of cooling fan relays. Their main difference involves the winding armature that they use to complete an electrical circuit.
Normally open relay
The most common type of relay uses an open armature. When the relay coil gets energized, the armature closes. The completed circuit allows the current to flow to the fan motor.
Normally closed relay
The opposite of the normally open relay, this type uses a closed armature. Energizing the relay coil opens the armature and completes the circuit.
Dual relay
This relay type uses two circuits, one of which employs an open armature while the other one has a closed armature. Thanks to its use of both armatures, a dual relay can conduct an electric current in both open and closed positions.
How Relays Work in the Cooling System
Okay, most people know that a relay is an electromagnetic switch. A standard relay has a primary circuit that magnetizes a coil with a steel core – this turns the relay on, with the magnetism pulling the secondary contacts together to close a circuit. These secondary terminals that carry the load of whatever the relay is switching.
Relays are used for all kinds of jobs on a vehicle, from accessories to engine control components – the radiator cooling fan is one of the more crucial underhood components operated by a relay, or sometimes by two relays. Fan relays typically carry from 30 to 50 amps, because fans consume a lot of current.
Everybody knows most vehicle engines are liquid cooled. Circulating coolant absorbs combustion heat from the block and the cylinder head by conduction, then carries the heat away by convection to the radiator, where the heat is released from small tubes into specially designed fins positioned so that air will pass through and carry the heat away. The radiator is technically referred to as a "heat exchanger" because that's what it does.
The vehicle air conditioner has a condenser – another heat exchanger usually mounted in front of the radiator – that also requires airflow – sometimes there will be two fans for this reason, and those fans may run at a lower speed at the same time, at full speed simultaneously, or one fan may run while the other fan doesn't.
Vehicles either have a module controlling fan speeds or those with 2 fans often use 2 or 3 relays working together so that the fans can run in series (low speed, splitting the voltage and running slower) in parallel (both fans receiving full system voltage at the same time), or again, just one of the two fans might be energized sometimes, depending on prevailing conditions.
Driving down the highway, air naturally passes through the radiator, but when the vehicle is sitting in traffic or parked and running, the fan (belt driven or electric or one of each on some vehicles) draws air through the radiator to reduce the temperature of the coolant, which then returns to the block and the head to absorb additional heat. This is the short version of how a cooling system works.
For a more complete discussion of the cooling system, read our article here.
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Can a Bad Battery Affect Air Conditioning in a Car
Source: https://www.carparts.com/blog/bad-cooling-fan-relay-symptoms/
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