The 1 A.M. Call That Wasn’t an ABB VFD Failure: A Distributor’s Multimeter Story

In March 2024, I got a phone call at 1:17 a.m. The plant manager on the other end was calm, but I could hear a line going quiet in the background. “The ABB drive is lit up but the motor won’t run,” he said. “No fault code. Can you come?”

My company is not the largest ABB VFD distributor in the region, but we do stock the common ACS355 and ACS880 units, and I handle after-hours troubleshooting for a few local plants. In eight years I’ve handled more than 200 rush calls, and almost none of them needed the component the customer thought they needed. That night was no exception.

The line was a dairy filler, which sounds simple until you realize it runs 24 hours. Every hour down was roughly $12,000 in lost production, and a supermarket truck was scheduled for pickup at 6 a.m. The pressure was real.

Everything Pointed to the Drive

When I walked in, the ACS355 was powered up and showing 0.0 Hz. No alarm history was visible. I switched the keypad to hand control and tried a run command. The drive accelerated to 10 Hz, reported no current, and then stopped when the motor didn’t move.

The drive wasn’t in a fault state—or rather, it wasn’t reporting a fault. That’s an important distinction. A VFD can be perfectly healthy and still not drive the motor if something in the output circuit is open.

There is a motor contactor between the VFD output and the 15 kW motor on that filler. It acts like a starter solenoid: when the PLC sends a run signal, the coil pulls in, the main contacts close, and the drive output reaches the motor. If that contactor doesn’t close, the drive is just humming into thin air.

What the Multimeter Said

I’ve been burned before by guessing. So I got my manual ranging multimeter from the truck and started checking the control circuit. If you are not sure about the AC voltage symbol on a multimeter, it is the V with a wavy line above it (~). The straight line is DC. Because this was a 230 V coil, I selected the 750 V AC range first. I have seen people try to use the 200 V range to read 230 V and think the meter is broken when the display shows a “1”.

Here is how to test a starter solenoid with a multimeter the right way: check resistance first, then voltage under load. After locking out the control circuit and verifying zero voltage, I set the meter to ohms. I checked across the contactor coil terminals—A1 and A2. The reading was around 126 ohms, if memory serves. That meant the coil wasn’t open or shorted; the solenoid itself was electrically healthy.

Then I re-energized the control panel and set the meter back to AC voltage. With the PLC calling for the contactor to close, I measured zero volts at the coil. That was the clue. I moved my probes back to the PLC output relay and saw 230 V. The relay was fine. The wire between the relay and the contactor was supposed to carry that voltage, but it wasn’t arriving.

It took about twenty minutes to find the break. The wire wasn’t snapped. The terminal block screw was tight on the outside, but underneath the ring terminal there was corrosion—green dust that should have been copper. I brushed the terminal, made a fresh connection, and closed the panel. The contactor pulled in, the ACS355 showed a few amps, and the motor was running at 45 Hz. The entire repair cost zero dollars in parts.

(Should mention: I chased one wrong wire before that. I thought the issue was the neutral side because the voltage reading was zero, and I spent several minutes checking grounds. The real fault was on the switched side.)

The Pricing Lesson That Comes After the Fix

While we were washing up, the plant manager asked the usual question: “Can you get me a spare ACS355? I’ll pay whatever it takes.”

This is where it gets tempting. As an ABB VFD distributor, I could have written a sales order right then. In a panic, people will pay extra for overnight shipping and a priority handling fee. But I’ve learned that the emergency parts sale either builds trust or destroys it.

I quoted him a number that included the drive list price, the overnight freight cost, a fixed 15% after-hours handling fee, and a note that the total would not change after the PO. It wasn’t the lowest quote he could get by shopping around. But it was every cost I knew about, listed before he gave me the order. The next morning, when another distributor called with a lower price and no delivery date, he stayed with us because no one wants hidden fees in the middle of a crisis. That’s the transparency principle, though I wouldn’t have used that term at 4 a.m.

I should add: transparent pricing doesn’t mean cheap. It means the price you see is the price you pay. I’ve learned to ask what’s NOT included before asking what’s included. The vendor who puts all fees on the first line, even if it looks higher, is usually the one who costs less in the end.

From Emergency Call to Training Day

A few weeks later, the same manager called back. The line hadn’t failed since, but he realized something: his maintenance crew didn’t trust the VFD because they didn’t understand it. He asked if we offered ABB VFD drive training.

We spent a day in their conference room and on the plant floor. I walked them through the ACS355 keypad settings, how to read the fault history, and why the “no motor current” screen can point outside the drive. Honestly, the training was more valuable than any spare part I could sell them. It was also a reminder that a VFD distributor’s real product is knowledge, not just hardware.

The Repeating Lesson

That night changed how I approach no-start calls. The event was trivial—a corroded terminal—but the temptation to blame the expensive component was real. From the outside, it looks like the ABB drive failed because it has a screen and fancy buttons. What people don’t see is that a VFD is only one link in a chain. If a motor starter or solenoid doesn’t close, the drive can’t do its job.

I didn’t fully understand how often that happens until I watched a plant almost pay thousands of dollars for a replacement drive they didn’t need. Now, if a drive reports healthy but the motor doesn’t move, I check the starter solenoid first. You can do it with any multimeter that measures ohms and AC volts, though I prefer a manual ranging model because it makes me stop and think about which scale I am using.

One caveat: this diagnostic path only works if your motor is wired through an output contactor or starter. If your VFD is connected directly to the motor, a no-start has a different list of causes. And if the contactor closes but the drive trips on overcurrent, the solenoid test won’t help. Context matters.

That dairy plant still runs the same ACS355. We stocked a spare at their request, but I never had to deliver it as an emergency. Sometimes the best emergency call is the one where the repair costs nothing—and the best sales call is the one where you don’t take advantage of panic.