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Electronic Materials


Subaru news: Brake-lamp woes and saw-blade tires

by Bethany Halford
April 6, 2019 | A version of this story appeared in Volume 97, Issue 14


Silicones blamed for switch glitch

Automaker Subaru is recalling certain models of its Crosstrek, Forester, and Impreza vehicles, blaming a reaction between silicone-containing consumer products and brake-light switches. The recall affects 1.3 million automobiles in the US alone, according to Dominick Infante, director of corporate communications for Subaru of America.

Silicone-compromised brake-light switches might not turn on brake lights. The brakes still function, but the problem increases the risk of being rear-ended.

Infante says the brake-light switch snafu “stems from the use of consumer products containing silicone that can seep into the brake-lamp switch housing and deposit a layer on the switch contact.” This causes the switch to lose conductivity, resulting in dead brake lights. Consumer products containing silicones include shampoo, fabric softener, and car-cleaning products.

Manoj Chaudhury, an expert in silicones at Lehigh University (and the owner of two Subarus), says the explanation seems reasonable. Silicones, he notes, have a special affinity toward most surfaces because their surface tension is low and the molecules are flexible. Silicones “can creep over most surfaces easily,” he tells Newscripts.

“Silicones, as a source of volatile oligomeric species, could generate a high contact resistance,” says Ralph Nuzzo, who studies the surface properties of electrochemical materials at the University of Illinois at Urbana-Champaign. Nuzzo suspects that microarcing of silicone-coated switches could oxidize silicon in the silicones to form nonconductive silica-like materials.

But Nuzzo finds one thing puzzling. “Silicones are everywhere, used in all kinds of commercial products and all sorts of places,” he tells Newscripts. They’re in sealants, adhesives, antifog coatings, and insulators. How is Subaru so sure that the silicones are coming from consumer products? “That would be utterly difficult to prove, it seems to me,” Nuzzo says.

How did the automaker rule out a source of the volatile species inside the car? Subaru’s Infante says silicon dioxide was found on the contact surface of the brake-lamp switches. “Furthermore, the investigation found there to be no products containing silicone used in the manufacturing process of any related parts,” he adds. That’s why Subaru thinks that consumer products containing silicone are the culprit in the switch glitch.


Those wheels look sharp

Credit: YouTube/Beyond the Press
Let it go: The saw-blade wheels might slow this Subaru down, but at least its brake lights work.

In unrelated Subaru news, Finnish factory owner Lauri Vuohensilta and his wife, Anni, recently swapped the tires on a Subaru Legacy wagon for giant saw blades. Lauri then drove the toothy-wheeled hatchback on a frozen lake while Anni filmed the demonstration for their popular YouTube channel Beyond the Press, which promises viewers “amazingly stupid action.”

Although the saw blades carved impressive grooves on the icy surface of the lake, they didn’t cut deeply enough to send the Subaru to a watery grave. (Watch the video at, but be forewarned: there is cursing.)

The Vuohensiltas first gained YouTube stardom with their Hydraulic Press Channel, which shows a hydraulic press smashing all manner of objects, including a bowling ball, a diamond, and a rubber duck.

Bethany Halford wrote this week’s column. Please send comments and suggestions to


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