The passage of time affects any vehicle. How much (as well as how) the car was used and maintained plus the environment it was used in are the primary factors in how much wear and tear any vehicle has. While we can’t undo what was done, we can certainly compensate for it as the need arises. Since I generally discourage purchasing a vehicle that’s in really bad shape, I don’t need to list the types of things that are usually only found in such basket cases. Instead, I stick to the more common types of problems that most people might run into in a decent vehicle, whether it’s been stored for years or regularly used.
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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Faulty grounds are perhaps the most common category of electrical problem. This can mean anything from a missing or disconnected wire to a problem caused by rust or corrosion where the ground is connected. Obviously, if a wire is missing or disconnected, it needs to be fixed, assuming there is no other underlying issue that needs to be corrected first, such as a short circuit. A wiring diagram tells you what grounds need to be present and where they need to be.
Wherever ground wires are connected, good metal-to-metal, rust-free contact is crucial. Use a wire brush, steel wool, sandpaper, or other suitable abrasive to remove any contamination from where the ground wire meets the body or component. Make sure the fastener is tight and doesn’t strip out when turned, thus creating a loose and intermittent connection. It’s often helpful to add extra ground wires, especially when an upgraded audio system or other electrical upgrades such as gauges, ignition, or lighting are added (I cover some of these upgrades later in this chapter).
Because all Mustangs are unibody construction, there is no need to electrically connect the body to the frame; they are already a single unit. However, it is still a good idea to run a relatively thick ground strap from the engine to the body, and another from the inner support of the instrument panel to the same point on the body. This helps ensurethere is a good ground for the ignition, gauges, and switches. It can also improve the performance of the radio and lights, in some cases.
The next consideration is the condition of the many electrical connections on the car. As with the grounds, any connection should be tight and free of rust or corrosion. It should be appropriately cleaned and/or tightened. For direct, visible connections this is usually fairly obvious. The bigger problems come from hidden connections in plastic or rubber housings or in the wiring harnesses. Even though older cars have far fewer wires than new ones, there are still hidden connections that can sometimes cause a problem.
Similarly, harnesses can sometimes get pulled from their clips or otherwise be stretched so connections become open or intermittent without being obvious. Water or other liquids can get into connectors and corrode the internal terminals until resistance increases to the point where the circuit becomes open or intermittent. The only way to resolve these issues is to carefully inspect the whole harness and look for any external signs of damage, leakage, or separation. Pull connectors apart to make sure the terminals are clean, and to the extent practical and/or necessary, test the continuity of individual wires/circuits with a test light or a digital volt/ohm meter.
There are no short cuts here. If the harness and/or connectors have a problem, you must carefully and methodically track it down. After you’ve fixed a current problem, take steps to prevent them from reoccurring. Make sure the harness is properly wrapped with tape or another suitable form of insulation, and that the connections are clean and tight. Use electrical grease or other suitable sealants to prevent new corrosion.
Except for shorts caused by component failure, most short circuits are the result of wear and/or failure of the insulation around the wires. This is often a result of the wire’s insulation cracking as it ages, so the conductor inside can then ground out somehow. Shorts can also often be the result of the wire rubbing against something such as a sharp edge until the insulation wears out. This is especially common where a wire goes through a metal panel or has been tied down too tightly and rubs. The repairs for both conditions are simple, if sometimes tedious.
The individual wires simply get replaced, ideally with wire of the same gauge and color(s), using the same type of termination. When whole sections of a harness need to be replaced, it’s often better to just get a replacement harness instead of trying to fix each wire individually. Well-known companies, such as Painless Performance, offer complete replacement harnesses that feature all the correct factory connectors. Some harnesses have additional features to accommodate various modifications and upgrades. However, for the wires and/or harness that are repaired, you must also make sure you used the proper grommets, wire guides, and other items, so the wires/harness are properly located and kept away from moving parts, excessive heat, and moisture. If you use zip-ties to secure the wires and/or harnesses at various points, make sure these are not too tight and cause wear or cause the wire(s)/harness to press against something that will cause wear.
Written by Frank Bohanan and Republished with Permission of CarTech Inc