Summer Heat, Batteries and Air Con in the Murraylands

This guide is for drivers around Murray Bridge, Mannum and Tailem Bend who want their vehicles to cope with hot Murraylands summers. It explains why heat shortens battery life, why air conditioning faults are often electrical, and the simple checks that prevent breakdowns on the hottest days.

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How hot it gets

Murray Bridge has a semi-arid climate with very warm, dry summers and mild winters. Its long-term average January maximum is close to 30°C and annual rainfall is only around 350 mm, but those averages hide the real extremes. On 24 January 2019, Murray Bridge reached 47.5°C. Runs of days in the high 30s and 40s are part of most summers.

The Bureau of Meteorology keeps long-term records from its Murray Bridge weather station, which opened in 1885. For a vehicle, what matters is not just the air temperature. A car parked in full sun on a hot afternoon has an engine bay and cabin far hotter than the air around it, and that's where electrical parts suffer.

Why heat kills batteries

A lead-acid battery works by chemical reactions, and heat speeds them up. That helps the battery deliver current on a hot day, but it also speeds up corrosion of the internal plates and the loss of water from the electrolyte. In practical terms, a battery that might last several years in a mild climate can wear out sooner in a hot one.

The catch is when the failure shows up. The damage is done in summer, but a hot engine starts easily, so a weakened battery can seem fine. Then the first cold winter morning arrives, the engine needs more current to turn over, and the battery can't provide it. Many Murraylands drivers find out their battery was cooked in January when the car won't start in June.

Testing and protecting your battery

A simple voltage reading tells you the state of charge, not the health of the battery. A battery can show a good voltage and still fail under load. A proper test uses a battery tester that checks how well the battery delivers current, and it should be done on a charged battery.

If you'd like to understand the process, our guide on how to test a car battery explains what's involved. For choosing a replacement that suits the heat and your vehicle, see car battery types explained.

Testing tells you where you stand. You can't change the weather, but these habits reduce the damage:

• Park in the shade or under cover when you can, especially for long periods.
• Keep the battery clean, with tight terminals and no corrosion.
• Make sure the battery is the correct type for your vehicle. Cars with stop-start systems usually need an AGM or EFB battery.
• Check that the battery hold-down is secure. Vibration makes heat damage worse.
• Have batteries more than three years old tested in autumn, before the cold arrives.

Air conditioning: check the electrics first

When the air conditioning stops blowing cold on a 40°C day, it's easy to assume it needs gas. Often, the fault is electrical. The system depends on fans, relays, fuses, sensors and switches, and heat is hard on all of them. Common electrical causes include:

• A condenser fan that has failed, so the system can't shed heat at low speeds.
• A compressor clutch that won't engage because of a failed relay, fuse or clutch coil.
• A pressure switch or sensor that is faulty or has a corroded connector.
• A blower motor or its resistor that has failed, so air won't move through the vents.

Refrigerant work needs a licensed technician

Once the electrical side is checked, the system may still need attention to the refrigerant itself. That work, including regassing, recovering refrigerant and repairing leaks, must be done by a licensed technician. Don't use DIY regas cans or open the system yourself.

Our guide on common car air conditioning problems explains the symptoms of different faults and which ones you can check yourself, such as fuses and whether the condenser fan runs when the air conditioning is switched on.

Cooling fans and engines in slow traffic

On the open highway, air flows through the radiator naturally. In slow traffic, at the lights in Murray Bridge or queued at a ferry, the electric cooling fan does all the work. If the fan, its relay or its temperature sensor fails, the engine can overheat quickly on a hot day.

Watch the temperature gauge in slow traffic and listen for the fan running after you park on a hot afternoon. If the gauge climbs while you're stopped but drops when you're moving, the fan is a likely suspect. Turning off the air conditioning and turning on the heater can help get you to safety, but get it checked before driving any further.

Heat on the wiring itself

Batteries and air conditioning get most of the attention, but heat also works on the wiring around them. Plastic connectors and insulation in the engine bay go brittle after years of hot summers, and a connector that cracks can let in dust and moisture. Earth straps and terminals that are slightly loose heat up further under load, which makes the problem worse over time.

Under the bonnet, look for connectors that have discoloured, cable insulation that has cracked near the exhaust or turbo, and any melted or burnt-looking plastic. A burning smell or smoke from wiring is a stop-now problem. Pull over, switch off and read our guide on burning smells or smoke from car wiring before driving any further.

Hybrids, EVs and the heat

Hybrids and electric vehicles manage the temperature of their high-voltage batteries with their own cooling systems. Their 12V battery can still fail just like any car's, and when it does the vehicle may not start or switch on. Testing or replacing the 12V battery is usually routine work. Anything involving the high-voltage system, including its cooling, must be done by a licensed professional with the right training and equipment.

For help with heat-related faults in town, see our Murray Bridge page.

Parts for this job

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Get it done: get a quoteDo it yourself: shop AGM batteries

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Questions Murray Bridge drivers ask

How long does a car battery last around Murray Bridge?

It depends on the battery, the vehicle and how it's used, so there's no fixed number. Heat speeds up wear inside lead-acid batteries, so batteries in hot inland areas often fail sooner than the same battery would in a mild climate. Have a battery tested once it's a few years old, ideally in autumn before the cold weather.

My air conditioning only blows cold when I'm driving. Why?

That often points to the condenser fan. At speed, air flows through the condenser on its own. When you stop, the fan has to do the job, and if it has failed, the system can't get rid of heat. Check whether the fan runs with the air conditioning switched on. A failed fan, relay or fuse is usually an electrical repair.

Can I regas my car's air conditioning myself?

No. Refrigerant work, including regassing and recovering refrigerant, must be done by a licensed technician. You can safely check fuses, look at whether the condenser fan runs, and listen for the compressor clutch engaging. If those all seem fine, book the car in with someone qualified.

Need an auto electrician in Murray Bridge?

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Run an auto electrical business in Summer Heat, Batteries and Air Con in the Murraylands?

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Not confident doing this yourself?

There’s no shame in handing it over. A local auto electrician can diagnose the fault properly and get it done safely, especially for anything involving brakes, airbags, hybrid systems or air-con gas.

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