Wiring problems and oil extenders

February 2020

Paul Abelson


Q. I’ve been having problems with my trailer lights for years. I check the wiring, replace connectors, change bulbs, and every few months I have more lighting problems. With trucks getting more and more electronic, I worry about what’s going to happen to my next truck.

A. The objective of checking wiring is to ensure that electrical continuity will be maintained between the source (battery, alternator or, now, solar panel) and the point of use (lamp, electric motor, data processor, etc.). To accomplish this, connectors and terminals must be secure, wiring must be flexible, well insulated and undamaged, and circuits must be protected from moisture and corrosive road salts and their vapors.

Start at the battery. Make sure there is ample capacity for your needs. Cables should be properly sized for the current they will carry, including hotel and starter loads, and they need proper insulation. Grade SGX may be adequate for cars, but TMC RP 166 recommends Grade SGR. It has a thicker, more robust insulation.

Alternator output affects batteries when accessories are used. For example, most trucks come standard with 160-amp alternators, but if you’ve added hotel loads (TV, refrigerator, cook top or microwave, etc.), TMC RP 178 recommends at least 185 amps, and probably 210 amps.

Since tractor wiring is well protected, we’ll assume your problems are with your trailer. If possible, replace discrete (point-to-point) wiring with a sealed wiring harness. Modular harnesses are available from your trailer builder and most lighting suppliers.

If that is not practical, discrete wiring must be examined. If sections must be changed, get the right gauge and grade. Grade TXL is good for household wiring, where there is no vibration or great temperature variations.

For trucks, TMC recommends grade GXL with stronger, thicker, more flexible insulation. It won’t harden and crack in truck use.

The way wiring is attached and the attachment mechanisms have major effects on electrical performance. Once again, avoid plain spade or loop terminals from hardware stores. While good for indoor use, they do not offer corrosion protection. The best terminals have heat-sensitive polymer coverings that, when properly crimped and subjected to heat from a heat gun or even a hair dryer, provide a waterproof seal all around the wire and the connector. The best have sleeves around the male connector that surround the female socket to protect it from moisture.

Even ring terminals are available with heat-sealing insulation. If these terminals are unavailable, or if you want to assure dry splices, cover splices with heat-shrink tubing. Before making a splice, slide a section of tubing long enough to extend beyond the terminals by about one inch on each side, usually about 3 to 4 inches total.

After completing the crimp and heating it to set its sealing material, slide the tubing over the splice and heat it until it conforms to the wires and terminals. That will provide the best seal. Proper crimping is essential. TMC references ratcheting crimping tools. They are sized to mate both the wire and insulation with the appropriate sections of the terminal. They exert the proper crimping force to both gripping surfaces. The tool won’t release until the crimp is correct.

When connecting to a battery, lamp, device or anything that is too bulky to be covered with heat-shrink, use a dielectric grease, available from all major lighting makers. Do not over apply. A little goes a long way. TMC RP 155 covers corrosion-protecting materials and the negative effects of over application.

One of my favorite corrosion protection and repair tools is liquid vinyl, sometimes called “electrical tape in a jar.” I keep it in my toolbox and have used it over terminals and to repair chaffed wire.

When checking wiring continuity and voltage drop, never probe into insulation. Even the slightest pinhole will allow corrosive salt vapors to enter the wiring and corrode the copper. Protect the integrity of the wire.

Q. The other day I came across an ad for what they call an “oil extender.” They claim that oil never wears out, just the additives do. Their stuff replenishes the worn-out additives, they say, and if you use the product you never have to change oil again. Is there any truth to this, or is it just another snake oil scam?

A. I’m not familiar with this product, but some of my contacts from TMC are lubrication engineers, so I checked with them. There is some validity to extending oil life by replenishing or fortifying oil with specific additives, but my friends all advise against any “never change oil again” product. These products may work in industrial gears that are in factories and not subject to the temperature variations and combustion byproducts engine oils are.

Additives that increase extreme pressure performance, minimize wear, minimize foaming and protect from oxidation and rust formation are consumed in use but can be fortified with oil conditioners for a short while.

Others, such as detergent and dispersants, isolate and remove soot, deposits and particulate matter by filtering them out of oil. Temperature fluctuations have a great effect on engine oils, especially on the oil’s viscosity. Viscosity improvers help, but eventually engine operations will break down oils, consume some additives and affect oils’ lubricating abilities.

If you choose to use engine oil conditioners, a practice that major oil suppliers discourage, change oil filters at regular intervals to remove particulates and suspended wear metals. Have an independent oil analysis lab test for any incompatibilities and use oil analysis regularly. That will tell you about the performance of your oil and when it will need changing. LL

For more Maintenance Q&A with Paul Abelson, click here.




Paul Abelson, senior technical consultant, is a longtime contributor to Land Line. He’s a member of the Society of Automotive Engineers and a member of the Technology and Maintenance Council. In 1995, TMC awarded him its Silver Spark Plug award. In 2006, he received the Lifetime Achievement Award from the Truck Writers of North America. Although he’s “retired,” he still makes a popular contribution to Land Line readers with “Maintenance Q and A.”