The Magic Of Heated Windscreen Washers And How They Started Setting Buicks On Fire

Heated seats, they make sense to me. Butts get cold, after all. Heated steering wheels, too, I suppose, if your little fingies are frozen. But beyond these common features, automakers have been heating other things, too. Having spent my whole life in the toaster oven of Australia, I’d never heard of the heated washer nozzle. 

Of course, much of the world gets colder than Australia, with temperatures reaching below freezing. It makes sense that vehicles sold into these markets would have equipment to deal with such conditions. Just like headlight washers and liquid tire chains and so many other winter oddities I’d never seen before. 

The simple fact is that windscreen washers have tiny nozzles that will easily freeze up with even a light dusting of frost or snow. The solution is to ensure they’re not cold enough to stay frozen when you actually need them to work. That’s where the heated washer nozzle comes in, pioneered by automakers in the colder countries. But some automakers have gone even further by heating the washer fluid, too—with disastrous results in one very ugly and public case. Let’s explore! 

Hot Noz

Most automakers set the nozzles up to automatically activate their heating function at temperatures of 41°F (5 °C) or below. The heating elements are typically small resistive heaters integrated directly into the nozzle assembly, and a simple thermo-switch is used to supply electrical power at lower temperatures. They draw minimal power from the vehicle’s electrical system and are really just needed to keep the nozzles warm enough to stop them freezing over. They’re a simple and efficient solution to keep the windscreen washers functional when you need them most. 

A full history of the heated washer nozzle is difficult to construct because automakers rarely brag about such minor conveniences. However, by browsing the world’s parts archives, we can get a rough idea of when they hit the market. 

My research indicates that German automakers were likely pioneers in this regard. BMW has been offering heated washer nozzles at least as far back as the E24 6 Series models of the early 1980s. The same washer nozzles were offered across the E30, E34, and E32 as well, and could often be specified alongside a heated driver’s side door lock for added convenience. Mercedes-Benz has offered heated washer nozzles since at least the W124 generation of the mid-1980s. 

As is often the case in the auto industry, eventually a technology is taken up by a wider range of suppliers and it proliferates on a wider range of vehicles. Volkswagen has been fitting heated nozzles to a range of its models since the early 2000s. The winter experts at partner company Skoda have been doing much the same, too, as have stablemates Audi.  In fact, most major European automakers have adopted them at some point or other, like Peugeot, and Volvo. Kia was the only Asian automaker that I could find to have obviously equipped vehicles with heated nozzles, though it’s plausible that others in the region may have also adopted the technology. As for the Americans, we’ll get to them in a bit. 

Generally, it’s quite easy to spot a heated washer nozzle when you’re looking at it. These nozzles tend to have wires hanging off or an electrical connector built in, in addition to the usual barbed connection for the washer fluid hose itself.

There is apparently a common misconception about the purpose of heated washer nozzles. Some, like the Kia dealer in the video below, believe that the nozzles are heated to warm the washer fluid in colder conditions. Indeed, some Kia documentation hints at this, too. However, this isn’t really what they’re for. If that were the purpose, it would be far more effective to warm the washer fluid reservoir than to try and apply heat as the fluid passed through a tiny nozzle. The fluid moves so quickly, and the nozzle is so small, that there would be an incredibly limited opportunity for heat transfer. Indeed, it’s unnecessary anyway, as washer fluid itself contains alcohol to avoid freezing over in cold climates.

Instead, the generally accepted purpose of the heated washer nozzle is to ensure the nozzle is not frozen over by condensation, frost, or snow. The rest of the system should be protected by the antifreeze component of the washer fluid; it’s just the nozzle that needs to be heated to avoid it getting blocked. 

Even with heated nozzles, it’s still important to use proper winter-grade windscreen washer fluid. That’s because only the nozzles themselves are heated. Regular water can still easily freeze in the reservoir and lines feeding the nozzles. If you’re in a properly cold climate, you’ll still want to be using proper winter washer fluid that can remain liquid at sub-freezing temperatures. The good stuff will work down to -30 F or so. 

You might assume that washer fluid dosed with anti-freeze compounds would negate the need for a heated nozzle, but it’s not always the case. If frost happens to block the nozzle while parked overnight, for example, the washer fluid won’t flow, no matter how hard the pump tries. If the nozzle itself is frozen over, the anti-freeze washer fluid just isn’t going to get there. Hence the value of a heated washer nozzle.

Mercedes-Benz actually has a particularly impressive implementation of this technology, too. Some time ago, engineers at the German automaker realized that regular washer nozzles were wasteful of fluid with their messy spray patterns, and that they tended to obscure vision when spraying. To solve this, they developed a feature called MAGIC VISION CONTROL, which is a very fancy way of saying “we put washer nozzles in the wipers themselves.” The laser-cut nozzle holes in the wipers are quite small. Thanks to their wiper-mounted location, it would also leave much of the windshield unsprayed if they happened to be blocked. Thus, Mercedes-Benz ensured the entire assembly was heated to ensure performance in cold conditions.

Your Move, Hotshot

Okay, so your wiper nozzles are hot, and that’s just dandy. But couldn’t automakers go farther? Why not heat the washer fluid itself? That way, it’ll have improved ice-melting power and will maximize your chances of having a clean windscreen. As it turns out, one American automaker did just that – with atrocious results.

Back in the late 2000s, GM rolled out heated washer fluid systems across its broad range. The feature was praised for its ability to clear heavy frost off a windshield without the need to scrape it by hand. It featured a special fluid-heating module from a company called Microheat. Plumbed in between the wiper fluid reservoir and the nozzles themselves, it was responsible for heating the fluid to high temperature before it hit the windscreen. Microheat referred to this as the “HotShot” system, which was initially marketed as an aftermarket device prior to the company linking up with GM.

The Microheat design used a unit that was separate from the main washer fluid reservoir. This meant it couldn’t unfreeze bulk fluid—anti-freeze washer fluid was still necessary. Regardless, heating the wiper fluid improved its frost-clearing performance in sub-freezing conditions.

Upon activating the system, it would take up to 40 seconds for the heating module to warm a shot of washer fluid for delivery to the nozzles. Under this condition, the vehicle display would display a notice on the dash—”HEATING WASH FLUID. WASH WIPES PENDING”—to indicate that the system was waiting for fluid to heat before running four wash/wipe cycles. Further wash cycles would only take 20 seconds of heating once the system was warm.

As covered by The Truth About Cars, GM had been working on the system with Microheat since 2003. It ended up becoming a key feature across a ton of GM models built for the 2006 to 2008 model years. You could get the system on the Buick Enclave and Lucerne, the Cadillac DTS and Escalade, the Chevrolet Avalanche, Silverado, Tahoe, and Suburban, and the GMC Acadia, Sierra, and Yukon. Even relative obscurities like the Hummer H2 and Saturn Outlook featured the same hardware.

Unfortunately, it wasn’t long before trouble struck. By 2008, reports were surfacing of engine bay fires, and NHTSA ordered an investigation. The washer fluid heating system soon came in for scrutiny and was believed to be the heart of the issue. As per NHTSA report:

ACCORDING TO GM, A SHORT CIRCUIT ON THE PRINTED CIRCUIT BOARD FOR THE WINDSHIELD WASHER FLUID HEATER MODULE MAY OVERHEAT THE CONTROL-CIRCUIT GROUND WIRE. THIS MAY CAUSE OTHER ELECTRICAL FEATURES TO MALFUNCTION, CREATE AN ODOR OR CAUSE SMOKE AND IN RARE CASES IT MAY CAUSE A FIRE. AS A REMEDY, GM DEALERS WILL INSTALL A WIRE HARNESS WITH AN IN-LINE FUSE.

The problem was believed to be in the control electronics for the washer fluid heater, with a short circuit causing a ground wire to overheat and cause a fire. GM’s solution was simple—it would install a small fuse in the low-current link that would burn out before the wire could overheat. The only problem was that GM had gone hard installing this system all throughout its range, and the recall population exceeded 850,000 vehicles in the US market alone. Fixing the installed population would be a tall order.

This owner rated GM’s system as “not bad, not that good.”

What the truck does this button do?
byu/Barry_McCocincider inChevyTrucks

Many thousands of GM vehicles shipped with this button, which would spray heated washer fluid onto the windscreen.

GM dropped its contract with Microheat amidst the disaster and sued the minnow company to cover the costs. Microheat promptly went bankrupt in late 2008, with the company’s assets purchased by M-Heat Investors, LLC. That company later filed a complaint with NHTSA suggesting that high-voltage transients in GM’s electrical systems were responsible for damaging the Microheat modules and causing the fires, but little came of the matter thereafter. Unable to hold up to the legal challenge of a billion-dollar automaker, the company was done for.

Things would only get worse from there. By 2010, GM was learning of further vehicle fires even in vehicles that had gone through the recall repair. In these cases, it was found that the washer fluid heating modules were still suffering thermal issues, either distorting or melting from intense heat, and in extreme cases, getting hot enough to ignite. The modules featured a thermal protection device that was supposed to shut the heating elements down in the event of an overtemperature condition, but they failed to work in some cases, with dire results.

Microheat believed their product was a winner. This low-resolution promotional video appears to be from around 2002, and features poorly edited fake shots of semi-trailers with Microheat branding. It’s very much of its time.

Burning cars generally equal panic stations, and in this case, it was no different. GM took decisive action. With Microheat dead and buried, there was little hope of coming up with a workable repair or replacement part, and this would be expensive to boot.

Instead, a new recall would see the systems removed from vehicles entirely, with owners compensated with $100 for the loss of functionality in their vehicles. Dealer techs merely needed to remove a fuse from the fuse box to disable the system. To be certain the pox was gone, they would also be instructed to remove the heater module itself to ensure it couldn’t cause any further harm. As covered by MotorTrend at the time, by this point, the recall population had swelled to approximately 1.5 million vehicles worldwide.

The idea didn’t totally disappear from the marketplace, even after GM’s expensive folly was over. Aftermarket supplier Alphatherm produces a similar system that uses a small heater to warm washer fluid up to 125 to 135°F in cold conditions. As per contemporary forum posts, some owners of affected GM vehicles chose to fit Alphatherm units in the wake of the second recall to maintain the unique functionality in their vehicles.

Funnily enough, as reported by Automotive News in 2010, Alphatherm was actually founded by ex-Microheat employees and ran out of the same offices in the wake of the bankruptcy of the original company. However, it was a shadow of its former self. Without the loss of both its GM contract and a pending deal to supply Ford, the new company limped on with just 10 employees in 2010, down from 120 at Microheat’s peak.

Alphatherm’s products have found a place in the aftermarket and appear to be effective at their task.

To this day, heated nozzles remain popular. They’re commonly included in winterized equipment packs by a whole host of automakers as mentioned above. Meanwhile, few are lining up to experiment with heating the washer fluid itself. The unnecessary complication ended up causing GM a whole lot of headaches, and it seems likely most other automakers will steer clear when regular antifreeze and heated nozzles seem to do a fine enough job.

Ultimately, today’s vehicles include a lot more fancy heated accessories than those of years past. You probably don’t notice a lot of them if you’re down in sunny California or dry Arizona. Regardless, for those in the freezier parts of the country, these technological advances can really come in handy when the wintry snows blow in.

Image credits: via Amazon, Microheat, BMW, Volkswagen, GM, Northern3000 via YouTube screenshot