Dabney (the heir to the paper clip fortune) owns well over 240 cars, as readers of his and the Doctor's adventures know. As everyone also knows, people who collect cars don't necessarily own vehicles that others would desire, and vice-versa. In Dabney's case, one of his more "eclectic" possessions is his 1978 AMC Pacer.
One fine morning the Doctor walked into the garage to see Dabney scrunched up under the dash of his Pacer. "It never fails to amaze me," said the Doctor, "the odd assortment of cars you collect. Case in point: this Pacer. It wasn't a particularly desirable car in its day, nor was it very well built, but still there's a small following of collectors."
"I know, Doc," replied Dabney, "but I always liked the bulbous lines of the car and the incredible outward visibility. There's more room in it than in most station wagons and I still don't know why they didn't catch on."
"Well, I think the main problem was that most people thought they were ugly, but beauty is always subjective. So what's the trouble, Dab?" asked the Doctor.
"My brake lights work just fine, but when I turn on the headlights the tail lights come on dimly and, after a while, the fuse blows. I've checked the bulbs and the wires but haven't found anything. The front parking lights shine normally."
Dabney could see that the Doctor was mulling over the situation. He didn't say anything for a minute or two and then said, "So the tail lights are dim and the fuse blows, but the brake lights are fine, eh?"
"That's right," said Dabney. "It's a bit weird, don't you think?"
"Yeah, that's true," said the Doctor. "If the brake lights were also dim I'd suspect the sockets themselves. However, it's most uncommon for both sockets to fail at the same time. Hmmm."
They tested the Pacer's brake and tail lights several times, just to make sure the symptoms were as Dabney described. Sure enough, both tail lights came on dim and the fuse blew within a minute or two. They also looked at the sockets to see if there was any corrosion. Nothing turned up as unusual.
"You definitely checked to make sure the bulbs are the correct types, right?" asked the Doctor.
"Not only that, I replaced them with new #1155 dual-filament bulbs just to make sure," replied Dabney.
"What bothers me is the slow fuse failure. That almost surely indicates a current leakage to ground," said the Doctor, "and it would also explain why the bulbs burn dim. We need to follow the wiring from the lamp fixtures to the dash."
They spent the next 20 minutes pulling up the rear floor matting to reveal the route of the wires leading from the dash to the tail light housings. The wires ran over to the left wheel well and were routed in such a way that damage would have been unlikely. Next, they pulled up the carpeting behind the driver's seat to see where the wire ran in that area.
"Looks like it runs from the step plate area in the door opening over to the transmission tunnel, doesn't it?" stated the Doctor.
"Why would AMC have done that," asked Dabney, "wouldn't it be safer to run the wire under the door sill all the way to the dash?"
"Yes, it would, Dear Boy," answered the Doctor, "but production engineering found out they could save some wire and some time by routing the wire this way. At the factory level it's all about saving time and money. Let's pull the carpet some more and see where this thing goes."
They pulled more carpet out and found that the wires met up with other wires coming in from the transmission (no doubt the reverse and neutral/park switch wires). From there they traced the new bundle of wires to the front of the transmission tunnel and under the center portion of the dash, where an aftermarket tape player had been installed.
"What's this," exclaimed the Doctor. "Looks like somebody put in an 8-track tape player and connected its power wire to the hot wire leading to the tail lamps," doesn't it?
Sure enough, they verified that the tape player's power wire was connected to the tail lamp wire, and it wasn't soldered. The connection was simply twisted together and wound with electrical tape, but over the years the bare wires had corroded.
"I'll bet this tape deck doesn't work either," said the Doctor.
Dabney blushed a little and said that it worked but ran very slowly.
The Doctor gave his knowing look and said, "What we have here is a classic high-resistance connection problem. Looks like we need to rewire this thing so that the 8-track plays. You won't have any brake lights, of course, but it'll be worth it."
Doc's sarcasm was totally lost on Dabney as he gave Doc a puzzled look.