Here is a typical wire schematic as shown in a PTO installation manual.
IF the power take-off (PTO) is the heart of a mobile hydraulic system then the electrical wiring is the central nervous system.
Given that the wiring is important, it is vital to set up and connect the wiring and electrical system carefully. An installation done correctly is essential to get the safest and best performance out of your mobile hydraulic application. There are a lot of changes and improvements in the PTO and mobile power application industry these days, and there are sure to be more improvements coming.
Having said that, the following is an outline of tips and best practices one can employ to help ensure the PTO and the mobile power system functions as intended. Common installation electrical problems and failure modes will be discussed to help in trouble shooting and protecting the vehicle’s electrical system and components.
First and foremost is safety. Working under a vehicle can be dangerous. Make sure the installers follow all the appropriate safety precautions. For example, do not attempt to install wiring while the truck is running. Do not allow the vehicle to inadvertently start, put the keys in a safe and secure place. Ensure the vehicle is stable and immobile while working on it. Also, be sure to follow your own company’s safety guidelines and practices.
There are not many special tools needed to hook up the wiring. Most tools are commonly found in any toolbox. Wire cutter, needle nose pliers, crimper, screw drivers and volt meter are the most common tools. The only special crimp tools that are needed are for the sealed style connectors. Sealed connectors are recommended for all connections that are done outside the cab of the truck.
To start any installation, remove the kit and open it up to survey what you have. Review the schematic in the manual. Most of the time, these schematics are very straightforward diagrams with clear instructions, part descriptions and an overall layout. They are not to scale either! Make sure you follow all safety precautions before attempting to install your electrical components and wire harness. With tools in hand and parts identified, you are now ready to get started.
For the best and safest results, disconnect the battery from the vehicle. Remember each vehicle is unique; be sure you are familiar with the body builder’s manual or contact a chassis representative before connecting and disconnecting components. Most installation kits come with a pre-made wire harness that is assembled for you. The routing of the wire harness is important. Run wires away from heat sources like the exhaust manifold. Use wire tie wraps to keep your wires neat and from moving mechanical devises like shift linkage and suspension components.
When plugging in connections ensure they mate completely and sealed. Most sealed connectors will plug together and lock together. Install the PTO indicator light and switch so it is easily visible to the driver. It needs to be in an obvious spot. Do not install or spice other electrical devises to Muncie indicator light switch wiring. This may cause high amp draw and burn out the switch.
Some PTOs come with a magnetic pick up sensor. If so make sure the proper gap is set for proper operation. The end of the sensor should not contact moving parts, if so they can be damaged and may need to be replaced.
- Remember to attach all warning decals and labels to the visor and dash.
- Good solid crimps are important. Check to make sure you have good secure crimps. It takes 20 pounds to pull off a good crimp for 18-gage wire.
- Soldering is the prefer method.
- Twisting wires together and black tape is never recommended.
- Find a good ground location and verify it by a continuity check. Some cab locations are not a good place for grounding. Some truck cabs are insulated from the frame to improve the ride for the driver. If this is the case your best bet may be to ground directly to the negative post of the battery.
- Locate and secure wiring using tie wraps to a solid sturdy location. Do not attach wires near rotating parts. Route wires away from high heat sources.
- Do not “hot wire” around fuses. Ensure the fuse is in the circuit and is in good working condition.
- Be aware of special circuit needs, some transmissions have a neutral lock-up feature and requires a separate circuit wired in.
- Some Oil/ATV/Grease/Hydraulic soaked wires/connectors can cause issues, possible grounding or shorting.
- Do not use or replace wiring with plain wire, use gas and oil resistant wires.
Troubleshooting a PTO’s electrical system, or that of any other mobile power system, requires the right tools, patients and system knowledge. It is essential to keep that in mind as you work through the process. Electrical issues may include wrong or omitted parts, bad connections and/or poor grounding. Typically, there should not be any new parts left in the installation kit or on the shop floor after the installation is completed and it is vital that the installer reads the instructions. One last major area deals with hydraulics and pneumatics and their relationship to electrical and mechanical functionality. Remember to contact your distributor or call the PTO manufacturer to help with questions or troubleshoot if you need any assistance.
Electrical troubleshooting follows the divide and conquer method. Again, make sure the engine is off, the vehicle has cooled down and there are no rotating components. Start at the furthest end of the system and check electrical connections. Work your way back toward the PTO. Are components showing any signs of cracks or defects from installation? Is there anything leaking? If bad parts are discovered, replace them with new parts from the manufacturer. Do not substitute used parts. That practice is problematic and extremely difficult to ensure reliability. Next, trace the wire routing and remove or fix any kinks or pinched wires because pinched wires may cause grounding. Make sure wires do not touch the exhaust pipes. Wires that are too close to a heat source can melt and ground out your system. Also, inspect each connection to ensure there is adequate contact. Use a multimeter to check voltage and continuity. If necessary, unplug connection and clean them. Remove any corrosion on bare wires/connections then reconnect. Clean connectors operate better, consistently and cooler, less resistance.
If wires were crimped, make sure the insulation on the wire is removed and the terminal is connected firmly to bare wire. Poor connections can become hot spots later and are more susceptible to corrosion. Step back and take a minute to review the system and the schematic. Verify you have all switches, sensors and other electrical parts in place. Confirm they are secure in their location and check to see if the wires are crossed. Verify connections are not loose or disconnected altogether. Omitting parts, poor connections, jumping wires and using inferior substitutes will reduce your PTO performance. You will then find yourself back under the vehicle fixing what you should have done right the first time. Another important point to mention is PTO integration with the engine control module (ECM). Vehicles are becoming more sophisticated and it is vital the PTO is properly “plugged in” to the vehicle. Check the connection and wire routing and as always, be sure to review the supplied schematic that comes with the PTO
If the PTO is not working as planned, simply step back and review the problem. Think about the mechanical, electrical and/or hydraulic and pneumatic features. Look around for extra parts on the floor or in the box. Divide and conquer to isolate parts to better evaluate their performance. Test and verify functionality whenever possible and use continuity meters, volt meters and gauges to quantify readings; you cannot just assume anything. Swap component parts with factory parts to identify bad parts and do not use old parts just to save money because it will cost you more money in the long run. The optimum PTO can be specified. The installation can be exacting; unfortunately, the unexpected happens and troubleshooting wiring is sometimes required to get the job done right.
Mike Essin and Mikel Janitz, Electrical Designer & Engineering Manager respectfully, work for Muncie Power Products in Tulsa, OK. They can be reached at firstname.lastname@example.org or email@example.com or visit by visiting www.munciepower.com