I have a 1999 Mercedes ML430 with 150,000 miles, and for the past bunch of years, occasionally there would be a ticking/clicking/clacking sound coming from the dash area. I determined that it occurs when the temperature dial is set all the way to the cold side, and my mechanic thinks it’s the heater gate getting stuck or trying repeatedly to close when it may already be closed. I suspect that pieces of insulating foam may be blocking the gate. (I’ve seen pieces of gray foam fly out of the dash vents when the fan speed was on high!) Is there an easy fix for this? The vehicle is quite old (although it drives well), so I don’t want to pay to have the entire dash taken apart to get to the problem area; however, the clicking noise is quite annoying in the summer, and I’m concerned that the gate motor might fail eventually. Thanks!

Well, there’s your easy fix for the clicking sound: The gate motor will eventually fail.

Those are called servo motors. They use little gears to move things — in this case, your ventilation system’s blend doors. The gears usually are made of plastic. And when a gear gets stripped, you get that clicking sound when it repeatedly tries to close the blend door and can’t.

If you can keep it from clicking by turning the temperature selector almost all the way to hot instead of all the way to cold, that’d be the cheapest and easiest solution. But I’m guessing you’ve tried that.

In most cases, to replace those servo motors, the dashboard has to come out. That’ll easily run you about $1,500.

So, is the clicking sound $1,500 worth of annoying? If it is, then I would have your mechanic replace all the servo motors and the fan blower motor while he’s in there. You’d hate to spend that kind of money and then have another electric motor fail a week later. And they’re all the same age.

I’d also have him replace the heater core while he’s in there. That also requires removing the dashboard, and if it starts to leak three weeks after you put the dashboard together, that will redefine “annoying” for you. Good luck.

I’m wondering if you would comment on tire-repair-in-a-can products like Fix-A-Flat for emergency tire repair. I am in the Navy and am trying to ensure that my wife has a backup plan to changing a tire if AAA is delayed for several hours (not a good thing with a 4-year-old in the back seat). Do these products work?

They often do work. There even are a few small cars that come equipped with that stuff in the trunk.

In the first Fiat 500 we test drove, instead of a spare tire I remember finding a can of “flat fixer,” a little air compressor and a bottle of Filippo Berio Extra Virgin Olive Oil. The oil must have been for dipping your bread in while waiting for the tow truck if the flat fixer didn’t work.

If you have a small hole in the tire — from a nail, for instance — or a slow leak around the rim, products like Fix-A-Flat can work well as temporary solutions. The can contains a liquid that’s injected into the tire, along with additional air. Once inside the tire, the slime hardens against the inside of the tire and, hopefully, covers up the hole.

But it’s a temporary fix. The idea is that it allows you to get off the side of the road and get home, or get to a tire repair place.

And it won’t work for every flat tire. If you have a gash in your sidewall, or you backed over the spikes in a rental car return lot, or sustained any serious damage, a can of Fix-A-Flat is not going to help you at all. Unless, perhaps, you can stuff the can itself into the hole.

And there are other limitations to keep in mind. The stuff freezes when it’s below 32 degrees. So if you live where it gets cold, and you keep it in your trunk, you may have to cuddle the can to your bosom in the passenger compartment for an hour or two until it turns back into liquid.

Also, there’s not much additional air in that can. So if your tire is really flat and riding close to the rim, the contents of the can won’t give you enough air to drive on.

You can address that by keeping a little compressor in the car, like the one Fiat provides. It’s powered by the car’s power point (aka cigarette lighter). It’s slow, but it gets the job done.

So, leaving a can of Fix-A-Flat in your wife’s car, along with a compressor, is not a bad idea. It may get her out of trouble someday. But because it won’t work on every tire failure, you want her to have roadside assistance, too.

And even when it does work, make sure she knows that she’ll need to get the car to a mechanic who can fix the tire properly with a patch or a plug.

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