Tire pressure affected by dropping temperatures

Posted11/5/2017 6:01 AM

By Doug McAllister

Q. Could you speak about tire pressure sensors. My 2005 Ford Explorer gets a low-tire warning every time the temperature dips. Over the years I have replaced many of the units and now one is leaking at the valve core and I'm looking at another $75 fix. Except for the leaking one, all tire pressures are correct. My 2009 Toyota Camry has the sensors also, but I never have had the same problem.

Is the problem with the Ford sensors? Are there aftermarket units? Are there any solutions short of replacing them with non-TPS valve cores?

-- Joe, Hoffman Estates

A. I suspect you are having problems with the Ford because it is a few years older. Typically, when the ambient temperature drops, the air pressure in the tires on your car drops a few pounds per square inch. If you had a tire that was a little on the low side and the temperature drops the tire pressure down another two or three psi, it could be enough to turn on the warning light. The sensor may be telling the truth.

As far as the leak goes, if the sensor itself is OK you can get a valve stem repair kit for most of the sensors and this is a lot less expensive than replacing the whole sensor. As a general rule of thumb, these valve kits should be replaced when you replace your tires. There are aftermarket sensors for most cars that can save you a little money and will work just fine. I hope this was helpful.

Q. I just finished reading your column regarding auto labor rates and agree with you 97 percent. Regular maintenance from a qualified mechanic can keep our cars safely running for 20 years. It is money well spent to have a dependable safe car.

Why only 97 percent? Because occasionally owners feel they are greatly ripped off. Case in point. Recently I brought my car to the dealer for an oil change, full synthetic, the works. And it had been a while since I had changed the cabin and engine air filters and I OK'd replacement of those, too.

Here's the rub -- the labor charge to replace each of those was $29 ($58 total). Cabin filter labor is understandable because they needed to dismount the glove box. But replacing the engine filter is four spring clips taking only one minute. You would think this would be a free labor charge in light of the work I just gave to them.

I did challenge the charge and was given the "minimum labor rate per step" answer. That charge angers me greatly and will live in my memory longer than all the good work they've done the past few years.

-- Ross, Mount Prospect

A. Great observations, Ross, and I agree there are some minor repairs that can be done as a complimentary service while the tech is working on the car. Some examples of these would be: air filters, wiper blades, light bulbs, license plates.

This is not meant to be an exhaustive list but just some of the items that are done at our shops as a courtesy, but not all of the time. Sometimes certain cars require more time to change an air filter than others, to use your example.

Occasionally there are brackets in the way, screws that won't come out and wiring connectors that have to be disconnected carefully so they don't break. Even license plates at times require the holes to be drilled and tapped and, needless to say, this can't be a complimentary service. We have had to remove bumpers to change a $2 light bulb before.

Your car is probably one of those that should be a complimentary air filter but you don't want to generalize because they aren't all the same. Once again, this raises the importance of developing that trusting relationship with a repair shop -- one that goes both ways. Thank you for your great input here.

• Douglas Automotive is at 417 W. Main St., Barrington; 123 Virginia Road, Crystal Lake; and 416 Northwest Hwy., Fox River Grove. For information, visit douglasautomotive.com. Send questions to underthehood@dailyherald.com.

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