Wiring Nightmares Can Be Avoided

by Andrea L. Algar
Motorheads Performance

In recent A/C work on a 1971 Chevy Chevelle SS, it became apparent that there were many issues with the wiring. The owner had body and paint work performed elsewhere, and had been talked into having this shop perform some interior upgrades. Unfortunately, the body shop had taken shortcuts, incorrectly installed, and used inferior products for which top dollar was paid when performing work on the interior, and when installing a new sound system. What Guy Algar, found when the car came in for repair was a mess of wires under the dash, some of which were cut and left hanging unattached to anything. It was small wonder why the parking lights and interior courtesy lights were not working properly! There was also a big ugly ball of wires which had been fed up the center of the car along the transmission tunnel, and came right up through the new carpeting in a very obvious position from the shifter up to the underdash!



1971 Chevelle SS incorrectly wired
with wiring coming up through carpet
at top of transmission tunnel and
anchored to the floor shift brackets.

 It is very disheartening to see the lack of workmanship that occurs much too frequently. This clearly demonstrates a lack of understanding of the electrical system, but also in proper installation of the interior components. Guy explains, "I value a shop that has a specialty and sticks to that particular area of knowledge and expertise. Far too many people get wrapped up in wanting to 'do it all', and neglect the very basics of doing the job well, and doing it correctly the first time!"



Chevelle SS being rewired 

in side panels and along
floor to front 

 Guy did correct the wiring mess, and everything works right on the beautiful SS. Wiring is difficult enough without having to undo a mess that someone else has created. It's sometimes difficult to understand another person's logic, and this is especially true when trying to make sense of a bad wiring job! Guy warns, "I hope that when you have need for wiring work on your classic car or truck, you check out your mechanic's experience with electrical systems, and get options for solving your problem. If you're considering the job yourself, make sure you're prepared for what may be in store for you. The vehicle's wiring schematic is highly recommended."

Sometimes a repair of the existing wiring is the easiest and best fix, but other times replacement of the entire wiring harness is a less expensive option! Guy relays, "I've seen some wiring harnesses come in to my shop with so many splices, wrong lugs or connectors, and incorrectly wired sections that they were beyond safe repair. Tracing each problem can take hours, and with multiple problems, it adds up quickly to an expensive repair. And, some electrical problems can be very elusive."



Incorrect Front Speaker Installation



Most wiring harnesses get messed up when newer sound systems and gadgets are installed. This was where the problems with the Chevelle SS started. The sound system was installed by the paint and body shop that sold the owner on a new stereo system. Remember, the person who may be great at fixing your transmission or doing your new paint job may not have too much experience with wiring or electrical issues, or in working with an older car or truck. Guy advises, "Unless you know how to read a wiring schematic and have the correct schematic for your specific car, it is best not to attempt a fix. Even a professional can make errors if they're not experienced with wiring."



Incorrect Rear Speaker Installation



If you have no other choice but to do the job yourself, it may be best to consider the expense of purchasing a pre-made wiring harness like those from Painless Wiring that are more or less "plus-n-play" installation. These companies provide harnesses which are configured exactly to  your specific car's year, make and model. And, you can add on for stereos and other options so that your harness comes with plenty of connections which are already correctly wired, the right length for installation in the correct place, and with the right type of connectors.



Guy cautions about installing components to your classic car yourself if you do not have wiring experience or knowledge. Incorrectly installed systems can wreak havoc on your battery, and even affect other components running off the power source. Guy sees far too many vehicles come in with shoddy splices, incorrect or absent grounds, and even use of incorrect power sources. Lights that do not come on, flicker, or work only intermittently are indications that something is wrong. Again, this Chevelle was having problems with its dash instruments, and we were asked to take a look. Guy found that what appeared to be a used instrument circuit board had been installed, but the technician had attempted to repair a broken circuit with a jumper (photo on left). It was not making a good connection, and was replaced with a new board (photo on right). Note that the new board leaves no exposed wires, as the wiring is all enclosed in the panel itself.



Replacement of new circuit board
was needed in order to complete
repairs to the dash instrument panel.



Another incorrect fix - with a jumper
being made on instrument cluster circuit board
to "fix" broken circuit to amp gauge.







 

Installing stereos and other components in cars prior to the 1980's was a relatively easy thing to do with a little understanding of wiring and taking the time to do the job right. Guy warns, "It should be noted that for newer cars, installing add-on components such as stereos is very difficult because of the computers they use for everything. Feedback from incorrectly wired components can fry your ECM, BCM or other computer systems which are very expensive to replace! ECM's can cost $500, $900, to $1600 or more depending on the type of car." Bottom line is to exercise caution when dealing with wiring issues. Take the time to check your technician's experience and ask for all your options so you can make a wise decision.

ABOUT THE AUTHOR:
Andrea L. Algar is co-owner of a classic car performance and restoration design shop in Leesville, Texas. Motorheads Performance specializes in repairs, maintenance, performance upgrades and restorative work on cars and trucks from the 1920’s through 1970’s. Her husband Guy L. Algar is a Mechanical Engineer with over 25 years experience. He holds 5 ASE Certifications from the National Institute for Automotive Service Excellence and has been working on old cars and trucks for over 37 years. Together they share their passion for old cars and trucks with other enthusiasts from around the country.