"You've got to be kidding," Tom said as we stood over the engine compartment, staring down at a 2011 Duramax diesel engine, "the serpentine belt is causing the transmission not to shift properly?" He was referring to a truck that was towed in for a transmission issue. Being the great technician that he is, Tom verified  the concern. Step one in good investigative work.
      Step two involves a good visual inspection to look for the obvious: rodent-chewed wires (Honda makes a rodent-proof electrical tape), add-on accessories, disconnected/damaged connectors--you get the idea.
     "This vehicle went to an upfitter and had an aftermarket clutch pump installed, and the serpentine belt was replaced to accommodate the extra length," he explained.
     "Ahah!" We did some research--step three--and found a document from the manufacturer, explaining how certain aftermarket serpentine belts can generate copious amounts of electrostatic charge on their surface. This field can discharge and affect the transmission control unit which is mounted near the belt. According to the manufacturer, the TCM needs to be moved away from the voltage-inducing belt and fastened to the top of the underhood bussed electrical center (what I used to call the fuse box).
     "Unfortunately, the wiring harness isn't long enough to allow me to do that," Tom remarked. I can move it, but how much is enough? Is there any way that I can measure the charged field?"
     "You could make an electronic electroscope," I suggested.
     "I will be forever grateful if you explain that one," Tom came back.



 

 

     "This little device, consisting of a 9V battery, a clip, a Field-Effect Transistor and LED, can detect one volt and with ridiculously high sensitivity. You may want to install a 1 Meg resistor in the gate leg to protect it from voltage spikes."

     Tom determined that he did not move the transmission computer far enough away from the voltage-inducing belt. He finally fabricated an extension harness, mounted the transmission controller on the fuse box per manufacturer recommendation, and the problem was solved.

     "Wow! A serpentine belt stopped the truck from moving! I guess it pays to be thorough in your investigation, eh?"

     "Always," I responded.

     He looked at the small electronic electroscope. "Neat device," he said, "what else can it be used for?"

     "Field distortions," I said.

     "Meaning?"

     "Ghost hunting."

 

Jack McGinnis, HiTech Investigations Inc., signing off.