Maintenance Q&A
Shimmies and squeaks

By Paul Abelson, Land Line senior technical editor

I'm having problems with my 7-pin connectors. Last year I replaced the cables a couple of times, but this year it seems to have gotten worse. I've had to replace them every month. Can I repair them? If so, how? Is there something I can do to make them last longer?

Unless the connector has a rubber or polymer cover molded over it, you can rebuild it. But that would not be as cost effective as maintaining and protecting the assembly. The major enemies of 7-pin connectors are abrasion, vibration and corrosion. Here are steps you can take to combat each one of these.

Abrasion: The outer protective surface can be damaged if it is left to drag and bounce on rear decks. The best protection for the assembly is a spring mount or a "pogo-stick" to keep the system suspended above damaging surfaces. You should also have a dummy plug so that your 7-pin connector is protected from moisture, dirt and corrosive chemicals when bobtailing. With today's harsh snow-fighting chlorides creating corrosive road sprays, you should never leave a socket or plug exposed. Check the covers periodically, too. Chafing of the protective cover also occurs when the hose or plug vibrates on the deck.

Vibration: Vibration can loosen fasteners and weaken electrical connections between wires and pins. Counter vibration by making sure plugs and cables are always suspended off the deck, especially when bobtailing for even the shortest time. When pulling a trailer, be sure the latching lugs on the plug and socket assembles are secure.

Corrosion: By far, the greatest amount of damage is caused by corrosion. The salts and brines used today form mists that penetrate any opening not completely sealed. Once inside the cable assembly, the salts and moisture combine to create electrolytes, causing reactions that corrode metals. That corrosion weakens the electrical connections and the ability of wires to conduct electricity. Left uncorrected, corrosion will also destroy the structural integrity of the plugs and sockets.

The Technology and Maintenance Council has a Recommended Practice, RP159, to address the inspection and maintenance of the 7-connector cable assembly.

Inspection should start with a careful examination of the surfaces. Look for signs of abrasion, cracks or cuts. If any inner insulated wires are visible, discard the cable. The sun's ultraviolet rays attack rubber and polymer coatings. Better quality cables have more UV stabilizers, but eventually they will be affected. Signs of UV damage are fading, hairline cracks and a brittle feeling. A coiled cable assembly should not show any sag along its length.

Check connector terminals for dirt and corrosion. If found, clean them with a wire brush and a corrosion cleaner. Otherwise, use water, but be sure to thoroughly dry everything. Use a hair dryer or heat gun. Special 7-pin plus and socket wire brush tools are available at parts stores and dealers. Never use pressure washers on unprotected electrical wiring. They can force moisture, salts and corrosion further into the wiring where they will generate more corrosion.

Once the assembly is thoroughly dry, apply a light coat of dielectric grease to protect metals and seal water out.

If the assembly uses split pins, make sure there is contact between pins and sockets. If not, gently insert a screwdriver in the split and carefully open the gap, a little at a time, until there is good contact. Too much force will break the pins. You can see the contact area by the amount of grease wiped off the pins.

You should check the assembly at every oil change or three months, whichever comes first. When you do, trade ends to promote even wear. Don't forget to re-grease the fittings, but go lightly on the grease. Use just enough to coat, not fill, the holes.

A few months ago, I blew a steer tire. The closest truck stop sent a local tire service company. They found a large nail in the shoulder area. Since the tires had only 6/32 of tread left, I kept the good one for a spare and replaced both. Lately I developed a wobble in my steering. It just felt weird. I took the truck to my regular dealer, and they wanted to replace my front wheels and all the front studs and hardware. Is this legitimate? What caused this? How can I avoid it?

First of all, be sure to have road service done by a well-known company with its own road service trucks. They generally follow approved procedures like those in the Technology and Maintenance Council's recommended practices. It is very important to make sure wheel fasteners are of good quality and torque limits are not exceeded.

Wheels are held in place by the clamping forces between the studs and wheel nuts. Under proper torque, the studs are stretched within their elastic load limit. Like a rubber band that is stretched, the steel stud wants to spring back to its original length, clamping the wheel in place. Too much torque, especially on substandard studs, stretches them beyond their elastic limits, destroying their ability to spring back and hold clamping force. The wheels loosen, holes are worn out-of-round, and you get the wobbling effect you experienced. Your dealer is probably right. The only corrective action after damage has occurred is replacement.

To avoid future damage, wheel mounting should be done manually with a torque wrench. Far too many studs and wheels have been ruined by mechanics with air-powered wrenches, especially those out of calibration. They figure, if a little clamping is good, a lot must be better. Not so with wheels.

You will also want to make sure to be aware of the shop's policies and recommendations on retorquing lug nuts after a tire service is completed. Warranties are often voided if you do not have the lug nuts retorqued within a specified number of miles. LL