Tips for Working on Windshield Wipers

Working On Wipers

Wiper service

It’s right after a major snowstorm, and there’s ice and snow on everyone’s windshield. You’re at the shop waiting for the phone to ring. The phone leaps off the receiver and it’s Captain Chaos; he’s managed to find a second use for his wiper blades. Apparently, Captain Chaos was in too much of a hurry to clean the ice off his wiper blades before turning them on. In his frantic attempt to go to work, the wiper blades have become completely useless. He can hear the wiper motor running, but the blades ­refuse to move.

Most likely, the nut on the wiper arm has worked loose from the wiper shaft. I haven’t seen as many wiper transmission failures due to snow or ice since most wiper manufacturers moved to this type of fastener. But, there’s always a Captain Chaos who will find a new way to break things.

The next generation of “frameless” or “aero” wipers is starting to become the norm on late-model vehicles, much to the chagrin of older drivers who only want to pay $5 for older-style blades. These new blades are designed to work for late-model vehicles, and a driver will notice reduced performance and wind noise if they try to go with a cheaper frame wiper. For older cars, these wipers can be a nice upgrade.

Diagnosing most of the mechanical parts of a wiper system is straightforward, but there are exceptions to every rule, so not every car will be easy. Diagnosing the electric or electronic components, however, is another issue. We can do a breakdown of systems by years, and then determine how to diagnose the problem and make repairs. Prior to 1995, there weren’t too many complicated electrical wiper systems. To go back even further into auto history, most wiper systems were either vacuum-operated or operated by hand. There are a few exceptions, but most of those are on special models.

After 1996, with the arrival of OBDII systems, a lot of the manufacturers tied their wiper systems into the ALDL connector. You can actually diagnose the wiper system with a scanner. Some even have codes that involve the wiper system, usually through the BCM unit or the CAN system.

I much prefer newer cars because of the diagnostic capabilities when using a factory scanner to operate the front and rear wiper systems. You can still diagnose the entire system with the use of an ohm/voltmeter, but if you ever get a chance to use a factory scanner, you’ll be amazed at how much simpler your diagnosis will be.

Wiper systems over the years have changed in terms of how they work, where the manufacturers put all the separate components and the nomenclature that each different manufacturer uses. For example, I pulled the wiring diagrams for Nissan Sentra, model years 1985, 1995 and 2005.

The 1985 model had a separate intermittent amp control module incorporated into the wiper system. It was mounted under the dash or near the fuse box. Its job was to control the intermittent level for the wipers.

By the time 1995 came around, the intermittent amp control module was now called a time control module. They both did the same job, but it was now mounted at the base of the steering column.

In 2005, everything got more compact. Now it’s a variable intermittent wiper control module, and it’s part of the wiper switch itself. If the test results tell you to change the wiper switch, the intermittent unit must be changed along with it.

Before tackling any electrical system in any vehicle, make sure you have the latest TSBs, proper wiring diagrams and any diagnostic information that you can get your hands on. Most good diagnostic manuals will have the impedance values and the voltage ranges in their test procedures.

Wiper motorsWindshield Sensors

Rain-sensing wipers are starting to become a popular option, and they are even standard on some import vehicles. Some newer models have eliminated the driver-controlled intermittent setting in favor of this option.

The rain sensor projects non-visible infrared light with LEDs onto the windshield. Next to the LEDs are sensor diodes that measure how much infrared light is reflected back. If the glass is dry, most of this light is reflected back. If rain or snow is on the glass, the light is reflected in different directions.

Rain sensors often perform double duty as sensors for automatic headlights. If there is a problem with the sensor, chances are both the lights and wipers will be affected.

The software sets the speed of the wipers based on how fast the moisture builds up between each wipe, but the newer systems use vehicle speed and information from the CAN bus for the wipe interval. This stops the wiper from flailing about at stoplights.

The rain sensor and module will also send information to the lighting module that controls the lights to turn them on if the wipers run for a predetermined amount of time.

One of the most common problems with these systems is not the sensor but the windshield itself. When a windshield is replaced, the glass installer could mount the sensor with contaminants or adhesive in front of the sensor. Some systems will detect that the wiping action is not affecting the amount of light that is being reflected back and might not allow the driver to select the auto mode. This is where the scan tool comes in handy.

Some replacement windshields may vary enough from the OE coatings, thickness and tints to also cause the sensor to malfunction.

The condition of the wiper blades can also influence how the sensor operates. If the blades streak or leave excess water on the windshield, the sensor will detect it and will increase the number of wipes to remove the water. When testing these systems, use a spray bottle that leaves droplets on the windshield. Do not use a hose because the sensor is designed to detect droplets, not a stream of water.

Most late-model imports use vehicle speed to determine the wiper interval. At lower speeds, the vehicle will increase the time between intervals. When the vehicle is put into park, the wipers may or may not enter into a hold mode.

Newer Lexus, Acura and Nissan models have controls that adjust the sensitivity of the sensor to the customer’s liking. The adjustment method can typically be found in the owner’s manual and involves navigating through the information display. This adjustment may help some customers deal with their control issues. You can also recommend new wiper blades to improve the system’s effectiveness.

Remind your customers, especially those in the northern part of the country, to make sure they turn off their wipers before parking their car for the night, and to clean the snow and ice off the wiper arms and blades before trying them the next morning. A little advice can go a long way, and, hopefully, keep Captain Chaos on the road and out of the shop.

You May Also Like

The April Digital Edition Is Available Today

Each issue includes technical content from Underhood Service and other ShopOwner channels.

The interactive and easy-to-use digital edition of ShopOwner’s April issue, featuring articles from Underhood Service, is available now.

Click Here to read the April issue

In addition to management topics and opinion pieces, this issue includes articles on how to think through a misfire complaint when diagnostic codes are absent; understanding when to flush an A/C condenser and when to replace it; the importance of lifters and their role in the variable valvetrain system; and more.

Spark Plug Fouling

Understanding why spark plugs get dirty.

Why Alternators Are Subject To Ripple Voltage

The alternator produces an AC current that must be converted into DC current by way of a rectifier.

Understanding Stop/Start Charging and Starting Systems

The problem may not have been caused by a complicated reason, something simple may have caused the system not to work.

Remanufacturing And The EV-Battery Challenge

One researcher is particularly interested in the fate of EV batteries once they reach the end of their automotive lifecycle.

Other Posts

Power Window Regulator and Motor Service

Power windows are great as long as they roll up and down when commanded to do so.

Battery Charging and Diagnostics

Here are six tips to use when diagnosing a vehicle with a dead battery. 

Caring For AGM And Flooded Car Batteries

Loose, corroded or damaged battery cables make poor electrical contact and can cause a battery to run down.

Read Your Copy of March’s ShopOwner Now

The new issue of ShopOwner magazine, featuring Underhood Service content, is now available to read online.