I like keeping good old stuff running as long as possible. One of my hobbies is to keep my 1988 Bronco II running; currently nearing the 400,000 mile mark. Over the years I have had to do some adjustments to the vehicle, especially since parts are getting harder to obtain. A few of these projects follow — all involving some type of electronic work. (And yes, there have been the mechanical fixes such as new heads on the engine at 310,000 miles and a couple of clutches.)
One of the recent items (which was not that fancy) was the rewiring of the dash panel. I got tired of having to replace a light bulb in the instrument cluster since it is a labor intensive task to pull the instrument panel to get to the light bulb. So, I decided to replace the light bulbs with LEDs. Fortunately, one can find an LED version of the main bulb type used in the dash lighting on eBay. And, since the entire dash wiring used a flex circuit that was getting a bit brittle after 20+ years, I decided to use as new set of connectors instead of the old ones so that the stress of removing the old connector from the flex circuit would keep the remaining copper traces in place.
Another project was a necessity as I ended up rewiring the headlight current path away from the steering column. In the original configuration, the headlight wiring ran through the steering column into the high-low beam switch. However, after years of operation I started to notice a warm plastic smell every time the headlights were on.
A bit of touching on the plastic that covered the steering column found the hot spot over the high-low beam switch module within. The solution was to wire up a solid-state relay box that used the existing switch and wire harness just to produce a control signal. Then pull power from the battery directly to drive the high and low beams. Figure 1 shows the details.
The last repair job ended up being a very simple fix that could have saved a lot of money. The 4×4 switching system decided to stop working one year. After some discussion with a shop and a diagnostic process, we found that the problem was in the transfer case where there was, as phrased, the “position sensor.”
This unit is considered non-serviceable and costs around $400 for the part. Now, as an engineer, I had to figure out how this “position sensor” functioned. After replacing the part and cleaning up the old one, I noticed some screws on the unit with special heads. Pulling out my security screw bit set and pulling the screws, I exposed the “position sensor” circuit.
To my surprise the circuit was essentially a circular board with circular traces and spring contacts to engage with the traces. The traces were dirty after the years of use. A bit of cleaning and the unit is as good as new — waiting to swap out the “new” unit when it decides to “fail.” If I had known how simplistic the “sensor position” circuit was, I could have saved some money.
Does anyone else have stories as to over-priced sensor circuits? How about some simple electronic repair on cars? Or am I the only electronics person who at times has greasy hands?