Electrical Repair Services Gainesville FL

Photo 1: The first diagnostic step was to lift the Taurus so I could run it in gear. Note the safety stands under the lift arms.

The original system used junction boxes rather than connectors and had only one fuse in the system.

All in all, I doubt if the system contains a dozen wires, two dozen at the most.

Growing up with this truck as I have, we converted to a 12-volt system when we replaced the original six-cylinder engine with a V8 back in 1968.

After installing a 12- to six-volt resistor block to operate the ignition and wiper motor, I ended up with the engine changing speed when I turned on the directions signals.

Photo 2: If you’re going to diagnose wiring failures, it pays to have a full complement of testing leads and equipment.

But, I’ve also kept busy this summer doing part-time mobile diagnostics.

Although most of the local shops have improved their skills, they still run across a few cases that they feel are beyond their diagnostic capabilities.

Case in point was a low-mileage 1998 Ford Taurus, which became this month’s Diagnostic Dilemma .

See Photo 1 .

During the summer, the speedometer on the Taurus would quit on an intermittent basis.

Of course, when the speedometer would quit, the automatic transmission would default into an intermediate gear and fail to shift into the higher ranges.

Photo 3: It’s not a perfectly safe solution, but wrapping some duct tape around the spinning lug bolts was the only way I could wiggle-test the wiring without catching my shirttail in the spinning rotor.

Because the problem seemed to be heat-related, the transmission shop felt that the Taurus’ PCM might be failing.

At wit’s end, the young couple who owned the Taurus visited one of my client shops, who then referred the problem to me.

I don’t like taking in retail work at my home shop, but my client shop felt the problem was beyond its technical capabilities.

The Customer Interview
The customer interview is a vital part of any diagnosis. In short, the couple who owned the Taurus indicated that the problem happened more often on a warm day with the windows rolled up.

Photo 4: Due to a voltage spike, the VSS output ranges from about 4 mph to 54 mph during the wiggle test.

The car would have to be driven at least 10 minutes before the failure occurred.

The overdrive light would flash when the speedometer quit working, which is normal on a Ford of this vintage...

Money was no object to the owner in repairing the electrical damage to his “decked-out” ’98 Wrangler.

The first case involved an owner who requested that a local shop replace the fuel pump because his ’98 Wrangler was slow-starting in the morning. The shop found the pump pressure was marginal and replaced the pump. Because the Jeep still had the problem, the owner complained about the fuel pump, first to the shop and then to the local jobber supplying the pump.

When the pump suffered a “complete failure,” the jobber recommended that the Jeep owner contact me. It didn’t take but a few minutes to confirm that the PCM wasn’t communicating with the scan tool.

The second Jeep failure was a ’92 Wrangler suffering from a no-cranking condition in which the owner had tried recharging the battery and jump-starting it, all to no avail. The owner had the Jeep towed to a local shop after he replaced the battery and discovered the Jeep still wouldn’t start.

An added cable powering an aftermarket winch or snow plow lift often seems to accelerate corrosion on the positive battery terminal.

My third case was another ’98 Wrangler , fully customized for off-roading. Because the owner had spent a great deal of money on the paint and mechanical accoutrements, money was no object in getting the vehicle repaired. Here again, I discovered that I had no communication with the PCM.

Three PCM Failures
The problem shared among these three Jeeps was a failure of the PCM to communicate with the scanner. In the first case, the owner knew the battery was failing, but neglected to replace it until his wife complained that the engine wouldn’t start when she tried to drive it to work.

He placed the battery on a trickle charge and returned at lunchtime to see if the Jeep would crank. It wouldn’t crank, and in frustration, turned his heavy-duty diesel battery charger to full boost. Then he noticed that the fuel pump wasn’t activating after he turned the key on.

A battery should maintain at least 10 volts during cranking. The power outlet mounted below the instrument panel is a convenient location for testing system voltage during cranking.