VFD Won’t Start? Fix Control Wiring Errors Fast
Estimated reading time: 6 minutes
Understanding Why Your VFD Won’t Start
Nothing frustrates a maintenance crew faster than pressing the start button and watching the motor sit idle. If your VFD won’t start, the culprit is usually a small control‑wiring detail. ABB, Lenze and Yaskawa all warn that the drive stays in a “not ready” state until every enable jumper, stop loop and safety channel is closed. Therefore, before you replace hardware, trace the wires.
This guide explains the electrical logic that decides whether the drive energizes the motor. We reference manufacturer manuals, UL 508A and IEC 61131‑2, and share proven field fixes so you can return to production quickly. Moreover, each tip relies on active troubleshooting rather than guesswork.
Along the way we link to resources such as our article on VFD overcurrent faults and the Yaskawa A1000 technical manual. Keep this page open while you work, and update your schematic after the repair is complete.
Five Control‑Wiring Mistakes That Keep a VFD From Running
1. Missing run‑enable jumper. Drives often ship with a factory wire across the enable terminals. If a previous installer removed it, the drive sits in “Disabled” even though no alarm flashes. Replace the jumper and the motor turns.
2. Stop circuit wired with the wrong contact. In three‑wire control the stop button must be normally closed. However, many panels arrive with a normally open mushroom switch. Consequently the drive sees a constant stop command and the VFD won’t start.
3. Sourcing‑versus‑sinking mix‑up. The digital inputs need a complete circuit. Tie the common to +24 V for sinking or to 0 V for sourcing, as shown in the Eaton PowerXL quick start. If you forget, every start signal floats and the LEDs stay dark.
4. Drive left in local mode. Pressing the Hand ∕ Auto key during commissioning is easy. Yet, until you return to remote, terminal S1 or DI1 does nothing. Always read the keypad and switch back.
5. Open Safe Torque Off loop. Modern VFDs disable all gate pulses when either STO channel is open. Close the STO jumper or complete the safety‑relay wiring before you chase other faults.
If any of these issues sound familiar, you are not alone. Precision Electric fields hundreds of calls that list “drive not ready” followed by at least one cause above.
Step by Step Troubleshooting When a VFD Won’t Start
Follow this logical checklist the next time the drive won’t run. First, verify the control mode. Press the LOC ∕ REM key or read parameter b1‑02 on a Yaskawa V1000. If it shows local, switch to remote. Second, use the input monitor. The panel tells you whether DI1, S1 or TB‑13A is high. If the contact does not toggle, fix wiring to that input.
Third, check for required jumpers. Yaskawa uses a Baseblock input, ABB uses Run Enable and Lenze labels the same circuit CE. Each must be closed. Fourth, confirm sink ∕ source jumpers or DIP switch. Fifth, read the fault log. Codes such as EF, STO, USP point straight to an open interlock.
When everything looks correct yet the motor refuses to start, measure voltage. In sourcing mode an active input should show 24 V to DCOM. In sinking it should show 0 V. Any half‑voltage reading exposes a floating reference that must be bonded.
Wire to Standards and Stop Repeat Failures
UL 508A and IEC 60204‑1 both require a normally closed, fail‑safe stop loop. They also recommend shielded control cable and single‑point grounding. ABB’s commissioning guide states that bonding shields at the drive end alone reduces noise that can flicker digital inputs. Therefore, wire your stop pushbutton with an NC contact, land the return on the correct common and ground the shield.
Moreover, separate control cables from motor leads by at least six inches. Use ferrules on stranded conductors to guarantee a tight termination. These habits cost pennies yet prevent hours of downtime. Additionally, label both ends of every conductor so the next technician can trace the circuit quickly. For extra details read our guide on VFD ground‑fault trips.
For further external guidance, review the ABB ACS550 user manual and SmartD’s comparison of two‑wire versus three‑wire VFD wiring. Both documents reinforce the rules explained here.
Case Study: From “Not Ready” to Running in Ten Minutes
A Midwest packaging plant recently installed a refurbished 20 HP ABB drive on an exhaust fan. The keypad showed “ready”, yet the motor refused to turn. Maintenance feared a blown power section. However, a quick check revealed that Digital Input 2, the mandatory Run Enable, was open. A spare piece of wire closed the circuit, the “Run” LED lit immediately and the fan ramped to speed. The entire fix cost less than a minute and nothing in parts.
This story proves two points. First, most “VFD not starting” events are logical, not electrical. Second, a systematic approach—reading the manual, checking each jumper and verifying input status—eliminates hours of guesswork. Because the plant recorded the lesson in its maintenance log, future technicians will solve the same symptom even faster.
Products That Simplify Start/Stop Wiring
Sometimes replacing outdated hardware is faster than troubleshooting for days. Precision Electric stocks AC variable frequency drives with built‑in 24 V supplies and removable terminal blocks. We also carry soft starters to tame inrush on legacy motors. Additionally, installing input line reactors dampens voltage spikes and extends drive life. Explore these solutions today and simplify your start/stop wiring. Our engineering team also offers remote start‑up assistance, so you can verify each control input over video before energizing the motor. Consequently, projects finish on schedule and without costly callbacks.
Pre‑wired terminal kits include the correct run‑enable jumper and color‑coded leads that match the diagrams in the manual. Consequently, you eliminate the number‑one cause of a drive not ready lamp—missing wires.
Keep Your VFD Running With Smart Wiring
In conclusion, ninety percent of “VFD not starting” calls end with a screwdriver and a short piece of wire, not a replacement drive. Now you know where to place that wire. Use the checklist, follow the standards and document changes. Consequently, the next time someone presses Start, the motor will spin and production will continue.
For additional troubleshooting help, read our articles on VFD overheating and drive autotune. Bookmark this guide today and share it with your maintenance team.
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