A three-year battery is normal here
A lead-acid battery has a chemical clock and heat runs it fast. Every ten degrees Celsius above ambient roughly doubles the rate of the reactions that destroy it — grid corrosion, water loss through the vents, and plate degradation.
Under a bonnet in Phoenix in July, that clock is running at several times its design rate for weeks at a time. Three years is a normal life. Four is fortunate. Five essentially does not happen unless the car lives in a garage and is driven at night.
The consequence for buying: replace on age rather than on failure. A battery entering its fourth summer is finished whatever a load test says in a cool March morning, and a load test in March is a test of a battery that has not yet been through the summer that will kill it.
The cooling system has nothing spare
Every engine cooling system is designed against a worst case. At 115 degrees, climbing, with the air conditioning at full load, that worst case is the ordinary Tuesday.
Three things follow.
- Marginal components fail here and nowhere else. A fan that engages a few degrees late, a thermostat opening slowly, a radiator with scaled tubes — none of these would ever be noticed in a temperate climate. Here they are the difference between normal and a temperature gauge climbing in traffic.
- Coolant condition matters more than the interval. Degraded coolant has lost its corrosion inhibitors and some of its heat transfer, and both are being asked for at once.
- Plastic goes first. Radiator end tanks, thermostat housings, coolant elbows and expansion tanks are moulded plastic, and heat cycling makes them brittle. They do not weep. They split, at once, usually while hot.
Ultraviolet is a component killer
The sun here does not merely fade paint.
Headlight lenses. Polycarbonate with a hard coat on top; when the coat degrades the lens hazes, and a hazed lens scatters the beam instead of projecting it. The car still has headlights and no longer has a beam pattern. It is a real safety loss and nothing on the dashboard reports it.
Rubber. Bushings, boots, hoses and belts harden and crack rather than wearing away. A control arm bushing here can be cracked through at a mileage where a northern one is barely worn.
Wiper blades. Months, not years. And the one time a year they are needed is during a monsoon downpour with a windscreen full of dust.
Interior plastics and adhesives. Dashboards, trim clips and anything bonded — including, on some vehicles, the bracket that holds the forward-facing camera to the windscreen.
Nothing seizes, and that is genuinely worth money
There is no road salt in Arizona and very little moisture. Underbody corrosion is close to absent.
A twenty-year-old vehicle here has fasteners that undo, brake lines with usable threads, and exhaust clamps that release. Jobs that need heat, penetrating oil and a plan in the salt belt are ordinary spanner work here. It is a large part of why Arizona vehicles are sought after elsewhere.
The corollary for repair costs: the labour estimate that assumes a fight does not apply, and buying a complete assembly to avoid a seized component is usually unnecessary. Here the component is often the right purchase.
Dust, and the filters that deal with it
Desert dust is fine and it is everywhere, particularly during the monsoon season when dust storms move a great deal of it at once.
Engine air filters load faster than an interval implies. Cabin filters load faster still, and a loaded cabin filter reduces airflow through the evaporator, which reduces air conditioning performance, which gets diagnosed as a refrigerant problem.
Check both by looking at them rather than by counting months. It is the cheapest maintenance decision available and here it is the one with the most obvious result.
Emissions testing, in two metros
Vehicle emissions testing applies in the Phoenix and Tucson areas rather than statewide, and the requirements depend on the vehicle's age, fuel and where it is registered. The current rules are worth checking with the state programme directly before an inspection is due, because the exemptions change.
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