Mustang Restoration Electrical Trouble Shooting Tips

There are far too many variations among the different models of early Mustangs to cover each one in detail, but I can provide some insight into problems that seem to have plagued multiple versions. There can be some significant hardware changes in a relatively short period of time, and I show how these affect the repair process.

The source of more common problems has more to do with the location of the components in the car and less to do with the design of the components. Therefore, exposure to the elements, chemicals, and excessive temperatures can cause the failure of many electrical components. Such is the case in the few examples I illustrate.

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This Tech Tip is From the Full Book, HOW TO RESTORE YOUR MUSTANG 1964 1/2-1973. For a comprehensive guide on this entire subject you can visit this link:

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Starting System

The starting system generally suffers from few problems if it is properly maintained. Other than for the battery, there should really be no need to replace any of the major components on a regular basis. If anything needs to be replaced, however, the parts are often available at local parts stores for relatively modest prices. Those needing exact authenticity for a show car should go elsewhere and may pay more. Whatever the type of project, the key to a trouble-free starting system is regular maintenance.

Charging System

As with the starting system, there is seldom need to replace the components in the charging system if it is properly maintained. The most common problem other than failure of the alternator or regulator is poor grounds and/or connections. These can cause improper charging and inaccurate gauge readings. These should be repaired, as previously described. A more recent issue is the lack of output of the factory alternator when modern equipment such as upgraded audio systems and electric cooling fans are added. I show how this can be easily addressed with only a slight change in the underhood appearance of the vehicle, if total authenticity is not necessary.

 

This graph shows the improvement in available spark energy of the Pertronix ignition versus breaker points. The benefit of doing this alone is considerable, especially at lower RPM. When combined with a more optimally matched, high-output coil, the results are even more impressive. More spark energy usually means better starting, faster acceleration, and improved overall performance including higher mpg.

 

A very common upgrade for early Mustangs is to convert the standard sealed beam headlamps to more modern H4 lamps. These Hella units give the higher light output inherent in the H4 technology and have a more sophisticated lens design that gives a sharper light pattern.

Ignition System

The ignition system of these vehicles is not so much prone to failure as much as it is prone to wear. Rarely does an ignition-system component completely fail. Rather, the performance gradually deteriorates to the point where the vehicle no longer runs acceptably. The primary reasons for this phenomenon are the ignition breaker points and the spark plug wires. While most people are aware of the need to periodically change the spark plug wires, distributor cap, and rotor, they neglect the need to maintain these even-more-critical parts. I show how to eliminate the need for any maintenance other than a periodic inspection for the ignition-triggering system and the spark plug wires. I also comment on choosing the cap, rotor, and spark plugs.

 

When installing higher-output H4 headlamps, it may be necessary to install a headlamp relay kit to get the highest output and avoid any problems with the stock wiring being unable to handle the extra current of the new lights.

 

Internal lights, such as this one on one of the rear seat trim panels, have bulbs that are easy to change. These can often be replaced with LED bulbs that cost more but are brighter and likely won’t need replacing.

 

 

After breaker points, factory spark plug wires are another source of frequent problems, especially for higher mileage vehicles. Over time, the internal resistance of most factory wires increases and reduces the spark energy available at the spark plug. This hurts performance and can even get to the point where misfires occur. The solution is to measure the resistance per foot of each plug wire and ensure it is within specification. If not, replace the wire(s). Even if the factory wires are okay, it’s still best to replace them with high-performance wires that use a spiral-wound metal conductor. These provide far greater energy to the spark plugs while also being more reliable and still preventing ignition noise from being heard on the radio. Highperformance spiral-wound spark plug wires are available in custom-fitted kits that are cut to the correct lengths for specific vehicles; they also look just like the factory wires in terms of color, diameter, and boot style. We used wires from Pertronix, which were a direct fit for our 302 “J code” V-8. They had much lower resistance than our factory wires and look great.

 

Our stock AM/FM radio was a very rare option, which, thankfully, was in great shape other than missing a pushbutton. Had we needed any repairs we would have surely left these to a professional. Unless your car has a rare/valuable setup, such as this, you can usually benefit from an aftermarket unit.

Lighting Systems

The various lighting subsystems on the car are some of the simplest and yet most critical systems from a safety perspective. Failures of various switches are common, but these are simple (if often tedious) and relatively inexpensive to replace. Bulb replacement is a common and affordable exercise and accessing the bulb typically determines difficulty. This may not always be the case, however. When water seeps through the gasket behind the plastic lens in the tail lamps, the bulb socket may become so corroded and/or loose due to contact with water that it needs to be replaced. New housings are easy, if not always inexpensive to come by.

 

This Custom Autosound radio looks just like the original 19641⁄2 to 1966 Mustang radio, yet it provides significantly upgraded capabilities— more power, a front/rear fader, and four speaker pre-outputs. It delivers vastly improved sound, can control a 10-disc CD changer, and has an auxiliary input to allow connection of and iPod or similar external devices.

 

The key is to use a new rubber gasket under the lens and to make sure it is properly seated to prevent the problem from reoccurring. Poor light output from any of the external lights is often due to poor grounds and/or other connections. Up to 1968 models, for example, the parking lights and turn signals share a ground wire. If the wiring is not connected properly the parking lights are overly bright while the turn signals are too dim. The connectors for the external lights in particular are prone to corrosion and should be checked/ cleaned regularly. I show how you can greatly improve the output of the stock headlights for relatively modest cost and effort.

 

Custom Autosound also offers radios with more features and power if you don’t mind a slightly less-factory look. This one also includes LCD display for song titles/station numbers, full electronic tuning, control of a power antenna, a digital clock, and 16 memory presets.

Audio System

As hard as it may be to believe, when most early Mustangs were sold they came with little more than a simple AM radio and a single, dash-mounted speaker. Very few people chose the more elaborate optional audio systems. In fact, the factory AM/FM radio in the 1968 fastback we used for much of this book was one of the main things that made the car a rare “1 of 1” vehicle according to its Marti Report.

 

Several kits, such as this one, are available to upgrade original Mustangs from manual windows and locks to powered systems that duplicate the function of the factory parts.

 

Our radio only needed minor repairs (replace a missing push button) and a mild cleanup. But had we needed to repair it, we would surely have sent it out to a professional. Other than for a show car and/or in a case like ours in which the radio is a rare option, there really isn’t much reason to keep the factory radio these days. Far superior options are available that bring modern capabilities and technologies to your early car while still retaining the factory look. The same applies for the speakers. If you decide to upgrade your factory radio, you may also want to consider upgrades to the antenna and the speaker wiring so you’ll get the most from your new unit.

Written by Frank Bohanan and Republished with Permission of CarTech Inc