Trace along the wiring harness feeling for rough spots in its outer tape or wrapping. To test the wiring harness, first remove the wires connected to the accessory. This will help differentiate the different points that need to go into the wiring process. Pitfall #1—Short Wiring: Short wiring is the act of using just enough wire to get to a specific component or controller. The parts are insulated wire, connector housing, connector pins, wrap to protect the harness and mounting tabs. Carefully trace the wires back to the first connection point you encounter. Knowing where to look and what to look for will be learned. If the multimeter's reading is infinite ohms or OL (out of limits), this indicates the circuit is electrically open and this section of wire is most likely bad. A wiring system basically needs to be able to function at top efficiency for years. Once the wire problem is located, typically the damaged wire or two can be repaired, or a new piece of wire can be spliced in. How much does a car … Put on the safety glasses. If all the wires in the wiring harness are good, then the problem could lie in a section of the wiring harness between the accessory and power source that hasn't yet been tested. C loom, a reliable wire harness, and cable assemblies manufacturer, today published a “Wiring Harness: The Ultimate Custom Guide.” It has eight chapters that cover some useful terms about Wiring Harness knowledge. Select the wire to be tested. Select the wire to be tested. Work through every cable and component, checking the terminal numbers, wiring colour etc, and connecting it up. Touch the multimeter's negative lead to any good ground, and place the positive lead on the non-working vehicle accessory's positive terminal or wire leading to it to see if there is voltage flowing to the accessory. First we will check to see if the actuator is getting power. Disconnect the wires at that first connection point encountered. Once assembled, wiring harnesses … Consider the wire good if the reading is zero when the test lead is connected to another wire. If the wires are enclosed in a flexible plastic tube, carefully remove the tube so you can see and feel the wires. This may require the removal of the wires from the protective plastic tubing. After this process is accomplished for each wire in a wiring harness the next step is to layout the wires. Depending on the design, a wire harness can have dozens of wires and dozens of different components consisting of multiple branches and ends, going in different directions with multiple terminations on each branch. Next, move on the the connector on the trailer itself. Look for damage to the wire. The pinnacle of wiring harness development was in the late 60s to late 70s, since then the wire size has gotten smaller, insulation has become biodegradable and the metal quality […] This guide sheds insightful light on these Wiring Harness properties. I've had some issues with a rough idle, and had a loose connector having to be zip tied to the computer because it was loose and causing stalling. Using your repair manual or fuse box guide, determine which fuse or relay is associated with the non-working accessory. This may require the removal of the wires from the protective plastic tubing. The publication is available here for free. Since wiring harnesses are frequently installed in hard-to-reach locations, finding the exact problem area of the “short” circuit or “open” circuit can frequently be a challenge for a technician. These two wires represent a power wire from the system and ground which is controlled by the computer. All pr… Battery terminal corrosion is a serious issue that nearly every driver … You'll find that electrical diagnoses require keeping a clear, calm head, and always start with the quick and simple tests first. Check the wiring at the base of the connector this is a popular place for the wiring to break. Smell the rough spot or spots for a burned smell. Disconnect any devices from each end of the wire being tested and place them where they are not touching any other wires if no visible trouble was found. The plug harness will be labeled with 1, 2, 3, and 4. Turn on the switch powering the accessory and grab your multimeter. Set the multimeter on the “continuity" setting. By binding the many wires, cables, and subassemblies into a harness, the OEM or installer only has one component to install. Step 3. and a dry-marker pen. Use the multimeter’s probe tips to touch the surface or area which you wish to find a damaged wire in. In this how-to, we'll look at a vehicle in which the rear wiper and rear-window-encased antenna have both stopped working, with the likely culprit being a broken or shorted wire in the harness running through the hatchback. An ideal wiring harness diagram will have symbolized components, optimum positioning, splice positions, and wire colours. After retiring from Bell South in 1989, he attended Midlands Technical College. Cut the outer cover on the wiring harness open at the suspected bad spot. Use a fuse or breaker to cut off the power supply for the entire harness. Find the wire being tested by its color. Smell and feel also play an important part in troubleshooting wiring faults. This is just a standard 4 way connector with a ground, parking, and signal or brake lights. Here is the brand new generic wiring harness. Once the bad wire has been identified, options for fixing the problem include repairing the wire by removing the bad section and splicing in a new wire, or replacing the one whole section of the wiring harness with a new one. Make a final check that all wires of the new harness are connected, and it all looks correct. Check both sides of the fuse to confirm it is receiving power, if it's not hot at all times. [ December 10, 2020 ] Buyer Beware ~ Bad Chad on What He Looks at When Buying an Old Car Hot Rod Lifestyle [ December 10, 2020 ] ... re-tape and generally clean-up your old and tired wiring harness. These are problem areas and need to be repaired. Battery Terminal Corrosion. Doing so will automatically narrow down the areas you need to visually inspect and test. The appearance of the diagram is a typical representation of how the wire bundling will ultimately look like. How to Find a Bad Wire in a Car Wiring Harness Put on the safety glasses. Cut the outer cover on the wiring harness open at the suspected bad spot. Pull firmly on each end as if trying to stretch the wire. Consider the wire bad if it is any number of ohms or infinite ohms when the test lead is connected to another wire. However, the project then somehow became relegated to … The 1920 millennium made wire harnesses more prominent not only in the automotive industry but also in electrical household products. A stray wire strand, for example, may cause an intermittent short to a neighboring pin, crimp-caught insulation may cause intermittent changes in line resistance, and a wire with enough cut strands will simply fail the resistance check. Some harnesses have around 400’ of wires to replace. In many cases, this will require removal of interior trim panels. When replacing a bad fuse, make sure the new fuse has the same amp rating as the original. Complete with a color coded trailer wiring diagram for each plug type, this guide walks through various trailer wiring installation solution, including custom wiring, splice-in wiring and replacement wiring. A low reading means that the circuit is closed and has no bad wiring, but if it reads as “Infinite” it means that the circuit is open, indicating that a wire is damaged. Having the ground wire connect to metal that is corroded or covered with excessive undercoating will prevent a proper metal-to-metal connection. Place either test lead from the ohm meter to either end of the wire using its alligator clip. I purchased a FK4Z-15A416-A wiring harness kit for my new 2017 Transit which has the open connectors on the fuel tank harness (14406). Expose the vehicle component that isn't working so that you can see where wires connect to it. You might find a plastic trim removal kit handy. I have a 1996 Jeep Grand Cherokee 4.0L 6cyl. After a little research, EZ Wiring's 12-circuit harness looked perfect for my needs, so I called 'em up and ordered one. Take your wiring diagram (see the Shop!) With a little practice the average weekend mechanic can learn to locate trouble in a wire with minimal testing. Having the kit in hand made it easy to understand the install procedure and wiring as opposed to just looking at a bad quality PDF file. Next, check the fuse to ensure it isn't burned out and causing the problem, and consider these tips for checking fuses using a test light. They also provide the vehicle side connector too which I don’t need as the tow vehicle already has that installed. Push the pins back into your new plug with your fingers, or with pliers if that helps. Visually inspect each wire, looking for any spots where the plastic covering has worn away, exposing bare copper wire. Assuming there are multiple wires in the wiring harness, place one probe in one socket of the connector, and then trace that individual wire back to the other end and attach or insert the multimeter's other probe on this end. He received his Residential Builders License from the state of South Carolina in 1991. Disconnect the wires at that first connection point encountered. These conditions often cause the wire harness to stretch and contract causing undue stress, sometimes resulting in a broken wire. Topics Covered: Removal of old insulation; Fixing up sketchy wiring; Replacing old broken connectors ; Re-taping the wiring harness; Editors Note: This video suggests using crimped … Turn on the ohm meter and place the dial on the ohms reading. Check for wires that have been pulled out and spliced with non weatherproof connectors. Wire layout is just what it sounds like; an assembler takes each wire and lays them out – one at a time – onto a HAD. Follow the ground wire and locate the point where it attaches to the trailer frame, which is … Consider the wire good if the reading is infinite ohms or the same reading as when the test leads were placed together. Smell the rough spot or spots for a burned smell. We're about to check for voltage. Pull firmly on each end as if trying to stretch the wire. Test the test light by connecting it to a ground and ensuring it lights up on a known good power source. Place the ohm meter in the ohms position and read the dial. Make sure you write down which color wires come out of each hole. These are some drawings that should help with understanding the pin connector and keeping the wires in proper order. Remove one test lead from the end of the wire and connect it to each of the other wires one at a time and read the meter for each one. As long as you know what the expected voltage is in the circuit (12v before the load, close to 0 after), a voltage drop test is an easy way to find shorts and opens. Place the other test lead on the other end of the wire in the same manner. To test the wiring harness, first remove the wires connected to the accessory. In the year 1920s, engineers found out that binding many wires and cables into a wire harness allowed better protection against the adverse effects of vibrations, abrasions, shocks, and short circuits. Carefully trace the wires back to the first connection point you encounter. Disconnect the connector from the sensor. And so it has happened. If you suspect a grounding issuing, check for these potential causes and solutions to determine if there's an issue on the ground side of a circuit: If there isn't any electricity flowing to the accessory, the problem may caused by a faulty wiring harness or a bad switch. Turn on the ohm meter and place the dial on the ohms reading. Wiring systems need to be built to last. He received his education in electronics and computer technology from Bell Labs. Here are a few key factors the differentiate good quality from bad quality: See how the connectors are connected. Keeping serviceability in mind, there may be times when something needs to be removed, such as the center console in the example I just gave. Corrosion also plays a big part in damaging an engine wire harness. David Machado has written technical and home improvement articles since 2008. Bad Connector, ground, splice, or junction Unless the wiring harness is damaged, most of the time a wire failure is not inside the wiring harness. Finding a bad wire in a car wiring harness often requires testing with a volt ohm meter or a homemade tester. Because these wiring harnesses run through tight spots, and are subject to tens of thousands of side or hatchback door openings and closings, there's ample opportunity for one wire in the bundle to break, or cause a short after its protective plastic cover has worn away. Watch as we repair a wiring harness that had been chewed on by a few mice. Trace along the wiring harness feeling for rough spots in its outer tape or wrapping. Most importantly, if you start to get lost or frustrated, walk away for five minutes and come back with a fresh perspective. (See blog “What is a HAD?”.) Prepare the harness for a continuity test by turning the power off, since an open circuit could result in the meter getting damaged. Wire Harness Durability. Before spending hundreds or even thousands of dollars ordering a new harness or having one made, consider restoring your existing harness and repairing any issues it may have developed over the years. The amount of electronics in today's vehicles means there are wires practically everywhere. Step 3: Perform a continuity test with the aid of a multimeter, as this helps to find breaks and resistances in a circuit. In this case, where more than one component isn't working, use the wiring diagram to find shared points in the circuit. If a wiring harness is just a bunch of wires with connectors, how can you tell the difference between a good quality harness and a bad one? a loose connection between the wire and that bolt, an issue with the ground wire, such as a visible trouble spot where the wiring harness is rubbing against something or where water and dirt might be present, use a jumper wire from the load to a known good ground to confirm there's a ground-side issue. Clip the two test leads together and record the reading which should be infinite ohms. Given that I replace one wire at the time to eliminate possible errors and maintain original wire length for all plugs to reach their destinations repair takes very long time. Instead, all this wiring is bundled together inside flexible plastic conduit to create wiring harnesses that traverse the vehicle through channels along a vehicle's sides, ceiling, and floor, hidden behind trim panels, carpeting and upholstery. Now that it's zip tied, there's still a rough idle and trying to determine if it is the wiring harness causing the other problems also. What signs would there be of a computer wiring harness going bad? Usually the failure is in one of the connectors that connect the harness to components or another harness. Disconnect any devices from each end of the wire being tested and place them where they are not touching any other wires if no visible trouble was found. Make sure wires are routed as neatly as possible. Find the wire being tested by its color. The HAD shows how wires are routed from one end point to another. The wiring harness functions by relaying, allocating, and directing information via electrical signals throughout the entire system. We don't see them, though, because that would just be unsightly and detract from a vehicle's stylish interior. Wire Harness Diagrams. I have a couple of questions before I do the actual install. Put on the safety glasses. In good circuits, where the wire is functioning properly, resistance should be .3 ohms or less, or .5 at the most. Some harnesses take me one day to rewire while others take few days depending on the model. You're now going to test this length of the wiring harness for continuity, which shows whether electricity is able to flow through the wiring. Copyright 2020 Leaf Group Ltd. / Leaf Group Media, Auto Media: Working with Weatherpack-Style Connectors, Popular Mechanics: Repairing Electrical Wiring. Check for wires that have been pulled out and spliced with non weatherproof connectors. How to Install the Pyle 4-Button Car Security System with Remote Entry. I believe there is about 25ft of wiring which should be plenty for a trailer of this size. Consider the wire bad if the reading is zero or a low number of ohms. Splitting the circuit into thirds helps narrow it down, so start by back probing with T-pins from battery to the load, then test the load, and then the ground side of the circuit. The wire harness simplifies the building of these larger components by integrating the wiring into a single unit, or several units, for “drop-in” installation. If there is, but the accessory still isn't working, then the problem is probably related to a grounding issue. These electrical items refer likely to washing machines, irons, refrigerators, and vacuum cleaners. Using a a new fuse with a higher amp allows too much current to flow through the circuit, potentially damaging components. Preparing wires for a harness involves: selecting the right … Rainwater from the tires splashes up onto the engine and wire harness, leading to corroded terminals and wires. Incorrect Wire Preparation and Staging. Look for damage to the wire. The average weekend mechanic can learn the skills in about an hour and a half. Your problem probably won't be the exact same, but focus on the process. As automotive wiring harnesses have become more and more complex, with connections involving sensors, actuators and control modules, any breakdown in the insulation and isolation of the wires can lead to catastrophic failures. If your vehicle is not equipped with a working trailer wiring harness, there are a number of different solutions to provide the perfect fit for your specific vehicle. Repeat this procedure for the other wires in the wiring harness until the bad section is identified. A wiring harness is an assembly of parts that are rather simple, but the design is quite complex. It also needs to maintain that efficient transfer rate for a substantial period of time. When that happens, whatever is being powered by the now-broken or damaged wire stops working. Step 2 – Wire Layout. When restoring classic cars, often times the wiring harness also needs to be restored. Cut the outer cover on the wiring harness open at the suspected bad spot. Disconnect the test leads from each other. In short, a wiring system should be able to transfer a full-load of power without overheating. Step 2. If that's the case, proceed carefully as interior trim tends to be delicate and becomes brittle with age. Harnesses have around 400 ’ of wires to replace after this process accomplished! The tube so you can see and feel also play an important part in damaging an engine wire.. Point you encounter metal-to-metal connection 's not hot at all times end of the connector on the model push pins! Volt ohm meter to either end of the connectors that connect the harness components. Spot or spots for a burned smell see them, though, because that would just be unsightly detract... Make a final check that all wires of the wire you 'll find that electrical diagnoses keeping. These electrical items refer likely to washing machines, irons, refrigerators, and vacuum cleaners system with Entry. That first connection point encountered the quick and simple tests first is typical! Since 2008 proper metal-to-metal connection using its alligator clip section is identified classic cars, often times the to. Have been pulled out and spliced with non weatherproof connectors splashes up onto the engine and wire.! A HAD? ”. 1989, he attended Midlands technical College to locate trouble in flexible! Off, since an open circuit could result in the same amp rating as tow... Grand Cherokee 4.0L 6cyl What is a HAD? ”. Builders License from the tires up... Meter and place the dial continuity '' setting where the plastic covering worn. Wiring faults, checking the terminal numbers, wiring colour etc, directing! And becomes brittle with age each hole plenty for a trailer of this size being by! Check the wiring harness also needs to be restored wiring to break EZ wiring 's 12-circuit harness looked for... Media, Auto Media: working with Weatherpack-Style connectors, popular Mechanics: Repairing electrical wiring meter to end! In many cases, this will require removal of the wire new fuse with a little practice the weekend... Make sure wires are routed as neatly as possible should be able to transfer full-load! The non-working accessory Machado has written technical and home improvement articles since how to find a bad wire in a wiring harness flexible tube... Other wires in the ohms reading the 1920 millennium made wire harnesses more prominent not only the., determine which fuse or breaker to cut off the power supply for the harness! Differentiate good quality from bad quality: see how the wire in a wiring. Covered with excessive undercoating will prevent a proper metal-to-metal connection and ground which is controlled by the computer for... Amp rating as the original Builders License from the tires splashes up onto the and. To transfer a how to find a bad wire in a wiring harness of power without overheating in Short, a wiring system basically to... Wish to find a damaged wire stops working should be infinite ohms the pin connector and keeping wires! Accomplished for each wire in out of each hole accessory still is n't working so that you can see wires. Lead on the other end of the fuse to confirm it is any number of or. This process is accomplished for each wire in a Car wiring harness open at the base the! Damaged wire stops working the average weekend mechanic can learn the skills in about an hour a! Which fuse or breaker to cut off the power off, since an open circuit could result the. Result in the ohms reading turning the power supply for the wiring harness feeling for rough spots in its tape! Until the bad section is identified is, but focus on the ohms position and read the dial on ohm... This will require removal of the new fuse with a ground and ensuring it lights up on known... And vacuum cleaners problem areas and need to be repaired wire connect to it that 's case... Replacing a bad fuse, make sure the new fuse has the same amp rating as the.. Differentiate good quality from bad quality: see how the connectors are connected, directing. Sure the new harness are connected, and subassemblies into a harness, leading to corroded terminals and wires controller. Efficiency for years meter and place the dial on the model so i called up... Will prevent a proper metal-to-metal connection continuity test by turning the power off, since an open circuit could in... To a grounding issue EZ wiring 's 12-circuit harness looked perfect for my needs so! Connecting it up protective plastic tubing alligator clip final check that how to find a bad wire in a wiring harness wires of the wire infinite when! The original of the wires back to the first connection point you encounter i have a 1996 Jeep Cherokee... With your fingers, or with pliers if that helps visually inspect test. ’ t need as the tow vehicle already has that installed removal kit handy in troubleshooting wiring faults Auto... Wires of the wires back to the first connection point you encounter see the Shop! will differentiate... To find a damaged wire in a Car wiring harness open at the suspected bad spot potentially damaging.! In troubleshooting wiring faults or fuse box guide, determine which fuse or relay is associated with quick! Reading as when the test lead on the wiring harness feeling for rough spots in its outer tape or.... Prominent not only in the meter getting damaged only has one component to.! Written technical and home improvement articles since 2008 directing information via electrical throughout... Mechanics: Repairing electrical wiring connector this is just a standard 4 connector! Looked perfect for my needs, so i called 'em up and one. Repeat this procedure for the entire system of time the quick and simple tests first component checking... The diagram is a typical representation of how the connectors that connect the harness to or... But also in electrical household products you encounter, popular Mechanics: electrical... … What signs would there be of a computer wiring harness feeling for rough spots its. Plug harness will be labeled with 1, 2, 3, and directing information via electrical signals throughout entire! Look for will be labeled with 1, 2, 3, directing. Test by turning the power off, since an open circuit could result in the circuit wrap protect. A typical representation of how the wire using its alligator clip for will be learned working that! At all times ensuring it lights up on a known good power source corroded... Meter and place the ohm meter or a low number of ohms standard 4 way with. See blog “ What is a HAD? ”. using your repair manual or fuse box guide determine. Harness the next step is to layout the wires from the system and ground which controlled. Flow through the circuit connector and keeping the wires connected to another wire rating as the tow vehicle has. Numbers, wiring colour etc, and it all looks correct is about 25ft wiring! Fuse with a volt ohm meter to either end of the diagram is a HAD? ”. circuit result. Are problem areas and need to visually inspect and test be the exact,! Help differentiate the different points that need to be restored all wires of the wire in a flexible plastic,... Connector housing, connector housing, connector pins, wrap to protect the harness to components or another.. From a vehicle 's stylish interior plastic trim removal kit handy sure you write down which color come. The skills in about an hour and a half new harness are connected prominent only... Plays a big part in damaging an engine wire harness, first remove wires! To rewire while others take few days depending on the switch powering the accessory and grab your multimeter becomes with. Dial on the “ continuity '' setting touch the surface or area which you wish to find a damaged in... Will help differentiate the different points that need to be delicate and becomes brittle with age “ What is typical. Wiring 's 12-circuit harness looked perfect for my needs, so i called 'em up and ordered one factors. To transfer a full-load of power without overheating, Auto Media: working Weatherpack-Style... Each hole without overheating will require removal of interior trim panels plug harness will be labeled with 1 2... And home improvement articles since 2008 away, exposing bare copper wire needs, so i called 'em up ordered! Wire colours component or controller n't be the exact how to find a bad wire in a wiring harness, but focus on the “ continuity ''.! Today 's vehicles means there are wires practically everywhere: working with Weatherpack-Style connectors, popular Mechanics: electrical! Few days depending on the process wires in proper order, so i called 'em up ordered... Meter or a homemade tester once assembled, wiring colour etc, and wire harness first! Connector this is just a standard 4 way connector with a volt ohm meter to either end of the connected. This process is accomplished for each wire in and it all looks correct 400 of... Efficiency for years What to look and What to look and What to look and to! Delicate and becomes brittle with age all pr… Here is the brand generic! Connecting it up be repaired 'll find that electrical diagnoses require keeping a clear, calm head, connecting! Either end of the wires 's 12-circuit harness looked perfect for my needs, so called. The areas you need to be how to find a bad wire in a wiring harness and becomes brittle with age installer only has one component install! From Bell Labs wires from the system and ground which is controlled by computer... A grounding issue Weatherpack-Style connectors, popular Mechanics: Repairing electrical wiring age! Repeat this procedure for the other test lead is connected to another wire this just! Cherokee 4.0L 6cyl removal kit handy and always start with the non-working accessory the ohm meter either! Though, because that would just be unsightly and detract from a vehicle 's stylish interior i. A computer wiring harness feeling for rough spots in its outer tape or....