Magnetic tow
lights need extra attention when troubleshooting because of the exposure
and movement they undergo. Here are three causes of tow light
failure:
Quick-Splice Connectors
Some brands of tow lights have
quick-splice connectors inside the base to splice the wires
together. Quick-splice connectors are rectangular, usually blue in
color, and sold under trade names like Scotch-Lok by 3M. Although
quick-splice connectors save the installer time because they don't require
any wire stripping, they tend to make a loose connection over time,
particularly when flexed repeatedly. To solve the problem, get rid
of all the quick-splice connectors in your tow lights and replace them
with conventional tubular butt connectors.
Unseen, Twist-Induced Short
Circuits
Being a creature of habit, I tend
to walk the tow lights to the towed vehicle, then walk them back to the
tow truck, and then coil up the electrical cable all in one direction
(clockwise, for example), the same way every time. Over time this
repeated coiling activity can twist the four electrical wires inside the
black outer cable jacket in the same way that you twist spaghetti when
rotating a fork. Eventually the wire insulation breaks and the bare
wires short out against each other. People tend not to believe they
have this problem because the black outer jacket on the electrical cable
remains unbroken while the individual wires inside have broken their
insulation. Fix this problem with new electrical cable or a new set
of tow lights.
Worn-Out Pins on the Tow Light
Plug
Each of the four pins on the
female tow light plug receptacle -- that is, the part with the flip-up
cover that's attached to the tow truck bed -- is actually split down the
middle to provide springiness and make a good connection. If the tow
light plug has been yanked out at an angle too many times, the two halves
of each split pin can be crushed together, making a loose
connection. Then the tow lights only work properly when you wiggle
the male plug in the female receptacle. Eliminate this problem by
installing both a new female and a new male plug. Out in the field,
you can also temporarily fix this problem by taking a small, thin-bladed
flathead screwdriver and gently inserting it between the two halves of the
split pin to spread the halves slightly.