The kicker: The glitch may not be the plug or connection at all. If you have good connections, check the voltages. The red wire should be battery voltage with the key on engine off. The gray wire should present 9 volts and the blue wire 0 volts with KOEO (key on/ignition off). If the problem still comes and goes when pushing on the plug, the alternator likely has internal damaged, in which case you’ll need to replace the alternator.
Our next problem with our dash display is at the other end of the car. It is not really as much of a problem in our wagon as it is in the hatchback version. You may never see this in your customer’s car, but it could show up early in its life cycle. It depends on how the car is used. If the car primarily carries passengers and does not carry much cargo, you probably won't see this one. But if the hatch is opened frequently for groceries, tools, or girl scout cookies, this one hits home.
The wiring harness in the hinge/hatch opening area experiences quite a bit of flexing. The obvious problems involve the rear lighting systems, lift-gate release, rear wiper and defroster, etc. But again, turn signals and warning lights tie into the dash. And once again, arcing creates frequencies and poor voltages that confuse our poor instrument cluster. In many cars, the first symptoms would be noticed by those following the car, but in this case the driver may see the dash act oddly before the rear lighting problems are detected.
Over time, the hatch harness wires get soft and weak. Soon, you have the hard-to-find open circuit. But as the commercial says, wait there's more! The wires can rub through their insulation and create shorts. Both the opens and shorts are intermittent in many cases. Once again the wiggle test is very helpful.
Here is a bit of caution. When you find one of these problems, do not attempt to perform a repair in the hatch area. The repair splice will be stiffer than the original harness, and will resist flexing when the hatch is opened, thus shortening the life of the repair a great deal, and could cause even more problems with associated wiring. Instead, remove the damaged wire from the hatch hinge area, and replace it with a new wire. Make the splices outside of the area of movement. While that does involve removing several interior panels to gain access, the result will be a longer lasting and better repair.
IGNITION SWITCH GLITCH
Once again, the entire dash display may simply behave oddly. As a matter of fact, sometimes the dash will be fine but the engine just won't start. Perhaps the dash is entirely dead, and the engine may or may not start. Once again, we are due for a wiggle test, but not to the wiring harness or connectors. Instead wiggle and bounce the ignition key in order to “wiggle” the ignition switch. The switch contacts become worn and start to make poor contact. Just a good bump in the road can change what touches and what does not. Shorting is not an issue, and the problem may simply involve poor contact causing circuits to come and go at random.
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