"Just One More Thing, Sir"

 

 

 

"We've been working on this car for months because the problem is so intermittent," Joe said, the owner of a family-owned repair business not far from where Jack McGinnis lives. Break out your note pad and ask the right questions on this one.

 

"The 2002 GMC Jimmy came in for inoperative door locks," Joe said. "It was simple enough to diagnose. The power mirror/locks fuse was blown. As I saw it, we had to make a choice. We could replace the fuse and see what happens."

 

"Okay," I said.

 

"Or, we could put a bigger fuse in the fuse block (original fuse is a 3-amp fuse)."

 

"Um--what else?" I asked.

 

"Put another fuse in it and perform the Power door locks inoperative diagnostic table."

 

"So, what did you do?" I asked.

 

"We put another fuse in it, operated the power door locks and power mirrors and it worked fine. The fuse didn't blow."

 

I wrote it down. "What else did you check?"

 

"I checked the wiring diagram. Circuit #840, an orange wire, fed the circuits. There isn't much on the circuit--mirrors and lock relay. I wiggled as much of the harness I could and the fuse was okay."

 

He explained that the problem must have been intermittent and everything checked out okay, so the customer picked up the Jimmy.

 

"And then?" I asked.

 

"Two weeks later he brought it back. The fuse was blown."

 

"You know what I'm going to ask, Joe," I said, writing notes.

 

"I do--there are no add-on components, no plug-in devices. No TSBs. I measured the current while operating the mirrors. Nothing unusual there. Same with the power door locks. The vehicle was not involved in any body shop repairs."

 

I wrote everything down.

 

"I told the customer everything looked okay, so he took it. This went on for about 3 months, this intermittent blown fuse. I wish I could put a bigger fuse in it and just ship it."

 

Here came the well-worn statement: "I checked everything and everything checks out fine. I thought there might be rodent intrusion chewing on wires but I didn't see any damage."

 

"Honda makes a rodent-proof tape," I mentioned.

 

"I didn't know that."

 

"Yep--check it out on Amazon. It goes for about $35. And as long as your there, if you want to read about some real-world diagnostic issues, buy my eBooks. The Electronic Killer and The Aldebaran Code." I figured I might as well hawk my books as long as he was on Amazon.

 

"Thanks--I will. So what about the Jimmy?"

 

"I would ask the customer to try to remember (by using a Columbo note pad or equivalent) what he was doing when he noticed the door locks or mirrors not working."

 

That was last week Wednesday. Joe called me up on the way home from work to tell me that the Jimmy would be at his shop. The fuse was blown.

 

"What was the driver doing at the time?"

 

"He was backing out of the driveway when his young son was sitting in the passenger seat, playing with the power door locks. Everything quit working."

 

"Ah-ha," I said, jotting it down.

 

"The driver said that come to think of it, every time they quit working he was backing out of the driveway, adjusting the power mirrors while his son played with the door locks."

 

"Now we're on to something," I said.

 

"Do you think that every time the transmission is put in reverse, a bare wire touches ground somewhere and pops the fuse?"

 

"Maybe," I said. "You checked for TSBs, right?"

 

"First thing I did," Joe replied.

 

"Did you check for Preliminary Information documents?"

 

"I don't know what those are."

 

I ran a PI search and scored a hit. "You have two choices," I said. The first choice is to put a 5-amp fuse in place of the 3-amp fuse, according to the PI document."

 

"Great," Joe said. What's the second choice?"

 

"Have the guy tell his son to quit playing with the power door locks."

 

"Got it," Joe said.

 

This is Jack McGinnis, signing off on a rainy night here in Wayne County.