A. There have certainly been many of them — some involved symptoms that defied reason, relative to the fix that resolved them. Others were really difficult and required an embarrassingly lengthy amount of time to resolve, or I failed to diagnose it right the first time and the car came back. Some of the problems that come in from readers certainly fall into the unusual category, but unless one is directly involved in the diagnosis and hands-on repair that fixes it, it's hard to know for sure how everything plays out.

My weirdest problem was 20 years back, during the winter, on a brand new Pontiac Bonneville. Our customer complained the CD player seemed to have a mind of its own, occasionally changing tracks, varying the volume, etc. The car was one of the very first, I believe, to have steering wheel control buttons for the radio and heater/air conditioner. After driving the car many times and perhaps once verifying the maddeningly infrequent demon, I tested, measured, and did my best to figure out why this could be happening, without success. Next, I followed Pontiac's advice by sequentially swapped the CD unit, steering wheel unit (a very expensive and complicated control device), translator module, turn signal switch, and all related wiring harnesses with an identical unsold new car. The problem would still occur, maybe once or twice at best, after driving the car for several hours under every imaginable condition (fast, slow, turning sharply, under power lines, over bumpy roads, and while operating other equipment)

The car had now been back to us perhaps three times — a very embarrassing situation — and my second call to Pontiac for technical assistance resulted in an engineer being dispatched, to arrive the following week. With one final idea up my sleeve- hoping to salvage my pride before the engineer arrived— I asked the customer to bring the car in once again (the idea would have proved fruitless, had I ultimately employed it). As I drove him home, I noticed he had opened the sunroof — he said it was his first and he loved using it, even in winter. As we neared his home, driving up a tree lined street/driveway, the CD player went nuts. We turned around and drove the street again, with similar results. Then it hit me! I closed the sunroof, we repeated the circuit several times, and the symptoms completely vanished. I opened the sunroof, re-encountered the symptoms, and fixed them by laying a cloth over the steering column/steering wheel intersection. Yikes! The rapid pulses of light/darkness caused by the sun and trees, time of day, open sunroof, at just the right frequency, was sneaking into the steering column, confusing the optical coupling inside. The back of the steering wheel contained several light transmitters (similar to a TV remote control) and the turn signal switch held several photo transistors. However the steering wheel might be turned, at least one of the optical couplings would always handshake. This clever but problematic system was soon abandoned, with the implementation of air bags, as the air bag clock spring allows a more sure connection between steering wheel buttons and the stationary steering column. The engineer was canceled, and a small plastic shield was ultimately developed to block entry of offending light pulses.