Motormouth: Corrosion is isolated

Q: My 2020 Toyota Sienna has a significant amount of corrosion on the positive battery post and nothing on the negative post. What causes this, and can it be stopped?

A: It’s called galvanic corrosion and usually occurs on the cathode, the positive terminal. You can remove it, but it often returns. To stop it, clean the battery terminal and the cable clamp. Battery terminal cleaning brushes are available at auto parts stores. Once clean, cover the terminal with protection. There are commercial products available, but I like to use silicone dielectric grease.

Q: What kind of battery does a 2016 Legacy Subaru need? Is an enhanced battery (and what is that?) necessary?

A: I’m unclear on what you mean by an “enhanced” battery. I have a hunch you are referring to an absorbed glass mat (AGM) battery, which cost more than traditional ones. AGM batteries’ acid is absorbed into a fiberglass mat instead of being a free-flowing fluid. No, you don’t need one. Your car will work fine with a traditional battery.

Q: I have a 1999 Mercury Grand Marquis. The fan control for the heat/AC works only on the highest setting. Is this a complicated fix?

A: How nice to answer a question about an older car where everything isn’t controlled by computers. In this case, the culprit most likely is the blower resister, which drops the voltage to the blower motor for all speeds but high. All it needs is to be replaced.

Q: We have been getting regular notifications that the remote capabilities on our Lincoln Nautilus are not working because of a low battery. We took it in to the dealer and were told that our phone and key fob are kept too close to the car (which is in our attached garage) and that it is constantly receiving pings/notifications. The key fob is probably 20 feet away, and our phones are 30 to 40 feet away.

A: I think you were getting the bum’s rush. Contact the dealership and let them know the problem persists. Leave your car there overnight, so it can be tested far away from your home, fobs and phones.

Bob Weber is a writer, mechanic and ASE-certified Master Automobile Technician. His writing has appeared in automotive trade publications, Consumer Guide and Consumers Digest. Send automotive questions along with name and town to motormouth.tribune@gmail.com.