On The Road

Like people, cars shouldn’t sit too long

By Matt Pataky

As the weeks pass during the pandemic, it has become clear to me that there are certain trends forming in the automotive world. This month, I explore the challenges and can hopefully help you navigate them or even stop them from happening.

The most obvious problem has been dead batteries. Even when a car is not operating, there is a small drain on the battery. Depending on the car, the drain or draw is usually between 60 milliamps (.06 amps) and 50 milliamps (.05 amps), though it can be much lower than that.

The lower the draw, the longer the battery will hold up. If a battery is less than three years old and is healthy, it should hold up – meaning it can start the car – for a month. If the car has a defective electrical component, it can cause a 1- to 2-amp draw capable of killing the battery in a matter of days. If you unintentionally leave the interior dome lights in the vehicle (a 3-amp draw), the battery will be dead the next day. Kids are often the biggest culprits; my 4-year-old turned on the lights in our minivan three times last month.

Getting proper sleep

Modern cars have so many control modules that it can sometimes take up to an hour before the car’s battery reaches its minimum draw – a process called “going to sleep.” It’s similar to what our computers and smartphones do.
It’s important that cars go to sleep correctly, however. If a control module has a problem, it can hold up the sleep process and drain the battery abnormally. If the battery is weak, it may not have the power to put the car to sleep or wake it up. While a mouse wakes up a computer, modern cars wake up when they are unlocked.

After about a month into the shelter-in-place, cars started coming into the shop with programming problems. We had two BMWs with batteries that were at least 6 years old. In both cases, we had to install new batteries and reset the camshaft variable valve programming. We aren’t sure what caused the program corruption – it could have been during the going-to-sleep or waking-up process – but the root cause was a weak battery.

Rodent relocation

We are also seeing something I have written about several times: the great rodent relocation. Because so many cars have been sitting in the same place for months, rodents have found the engine bay of your vehicle to be an upgrade from the ivy patch.

Make sure to at least open the hood to see if there’s any rodent activity. Rodents love to eat the hood insulation and then stuff it in the intake manifold to make a cozy bed. If you see rodent droppings, twigs, bottle caps, chewed wires, chewed hoses or trash, it is time to take action. The sooner you stop their activity, the better.

I have no iron-clad remedy for keeping the rodents out of the engine bay, but I suggest setting traps outside the car and looking for an environmentally safe rodent spray. After we repair the damaged wires or hoses, we install rat tape, which stops the rodent from ever eating the wires or hoses again.

Just because your car has not been driven much lately does not mean everything is OK. Open the hood and check for rodents and try to find out the age of your battery.

Matt Pataky owns Sunnyvale Foreign Car Service, 15 Pioneer Way, Mountain View. For more information, call 960-6988, email This email address is being protected from spambots. You need JavaScript enabled to view it. or visit sunnyvaleforeigncar.com.

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