The fool's gold of truck service

The fool’s gold of truck service

More decades ago than I care to remember, some movie or folklore led me to start panning for gold in the dirt road outside our home. Slushing a pan full of dirt around in a pan with water from the garden hose rather quickly revealed the road to be a mother-load of GOLD.

The bright flecks floating to the top of the dirt in the pan glistened up at me in the sunlight. Carefully, I scooped the gold off the dirt and into my jar. As my gold dried, it turned black. No longer sure about this gold, I sought out the expertise of a higher authority, my Dad. With a chuckle he told me that it wasn’t gold at all but fool’s gold, or iron pyrite. My illusion as a rich gold miner quickly evaporated. “But how do you tell the difference between fool’s gold and gold?” I remember asking in despair. My Dad responded, “They test it.”

Spring forward a few decades. A service truck comes into the shop with a transmission shifting issue. A quick check reveals several shift solenoid low voltage codes. Going through the preliminary electrical diagnostic checks fail to identify what or where the low voltage condition originates.

I clear out the codes and take the truck for a drive. Sure enough, before long the problem happens again. Clearing the codes again, I monitor the voltage to the shift solenoids. Both solenoids operate correctly–cycling on and off with the corresponding gear–at least until the air conditioning cycled. Then the voltage dropped, and the low voltage codes reset.

The problem source was narrowing. Arriving back at the shop, I started looking at the wiring to the recently installed air conditioning system. Whoever installed the air conditioning system found a wire with key-on power and tapped into it to power the air conditioning compressor clutch.

While the circuit voltage provided enough power to illuminate a test-light, it was not enough to power the transmission shift solenoids and the compressor clutch. Finding a hot wire under the dash can be fool’s gold; it looks good but it’s really just creating a new problem.

Gone are the days when the technician could just tap into a hot wire to power radios and other add-on accessories. The voltages present in many circuits are less than battery voltage and power sensitive electrical components. Splicing into circuits can cause any number of other problems that can lead to failures of costly components or assemblies.

Now more than ever before, technicians must consult wiring and circuit information before using a circuit to power other equipment. Manufactures generally provide additional fused ports to accommodate electrical accessories.  So the takeaway is this: Power in a wire can be fool’s power. Make sure it’s the right power intended to be used for accessories.                  

Additional tips for repair and maintenance of Class 4-8 trucks may be found in the Mitchell 1 ShopConnection Truck blog.

You May Also Like

Cox Automotive expands Great Dane presence in eastern Michigan

Trudell Trailer Sales, a Cox Automotive company, will expand into a new region.

Great Dane announced that Trudell Trailer Sales, a Cox Automotive company, is expanding into eastern Michigan.

With this expansion, Cox Automotive says it aims to extend its reach and support customers across Eastern Michigan to deliver maintenance and parts support for trailers sold at their dealerships, as well as for the trucks transporting them. Additionally, by opening a physical presence in Eastern Michigan, Cox Automotive says it plans to create local jobs and contribute to the economic development of the region.

CalAmp announces passing of president, chief executive officer Jeff Gardner

Jason Cohenour, director on CalAmp’s Board of Directors, has been named interim chief executive officer by the board, effective immediately.

Innospec joins the Diesel Technology Forum

Innospec is a specialty chemical company with employees in 25 countries around the world.

Safe Fleet acquires rolling tarp system provider

The existing leadership team will continue to manage the business post-acquisition.

Amerit launches Reefer Tech Academy

This program is designed to equip technicians with the knowledge and experience to understanding of refrigeration systems.

Other Posts

Photo Gallery: Driving Volvo Trucks electric European lineup

Behind the wheel of Volvo Trucks’s zero-emissions European lineup and what it might mean for the U.S.

Answering the biggest zero-emissions trucks questions

Volvo Trucks fields questions from what type of zero-emissions technology will work for certain applications and how it impact fleets.

Volvo Trucks on its global zero-emissions trucks strategy

Hydrogen fuel cell development, electric truck technology and infrastructure rollout dominates the conversation.

Using artificial intelligence to make a real impact on driver safety

Click! It’s the sound of safety. As soon as the driver pulls the door closed, the seat belt should be buckled. It should be automatic, a habit of muscle memory built over time, especially with highly trained commercial drivers. But it’s not automatic. A recent study by Verizon Connect indicated that more than 10% of