Load error (WP20 and WP25) and load out of range (WP50) are the same condition: the weight signal reaching the processor is faulty, or the load on the sensors is beyond what they can take. Unlike most Tecweigh messages, it usually means real hardware, not a setting. Prove whether the load count still responds before anyone unbolts a load cell or orders a part.
We’re an independent service company, not a Tecweigh dealer or agent. For bookings and parts, see Tecweigh belt weigher and WP-series servicing. For the other messages, see what the messages on a Tecweigh WP50 mean and Tecweigh WP20 and WP25 fault codes and calibration.
What does load error or load out of range mean?
On the load cell frames (WY15 and HY15 with two cells, WY25 and HY25 with four), it means the signal from a load cell is faulty, or the weight on the cells is beyond their capacity. The WP50 states it as a measurement: the signal has gone below 0 mV or above 15 mV. Those point different ways. A negative signal points at wiring or orientation; a high one at an overloaded, jammed or damaged cell.
The judgement is made at the scale card at the frame, not in the processor. On the displacement frames (WY10 with two LVDTs, WY20 with four), the same message means a faulty LVDT signal, so the frame plate tells you which sensor you’re chasing.
What’s the one check before anything is unbolted?
All three manuals start with it. Watch the raw load count and lower the calibration weight onto the frame. Weight down, count up. With the belt stopped, the count should be higher with the weight down than up, steady, and never negative.
If it doesn’t, the problem is in the load cells, LVDTs or scale card, not the processor, and calibrating is pointless: a zero and span is just maths on the numbers the sensors hand over.
Which messages point at the load sensing?
| Message | What we check first | When to call us |
|---|---|---|
| Load error (WP20, WP25) or load out of range (WP50) | Load count with the weight up and down, then orientation, wiring, terminals and jammed material at each cell. | If the count won’t respond, or the message comes and goes. |
| Zero counts low (WP50) | Shipping stops still fitted, a blocked weigh frame, then a damaged cell or scale card load input. | If the frame is free and the count is still low. |
| Span counts low (WP50) | Was the weight lowered? Does the count rise when it is? | If the count doesn’t rise with the weight down. |
| Span below zero (WP50) | The weight the wrong way round for the zero or span. | If the sequence was right. A cell fitted or wired backwards can do the same. |
A weak sensor can look plausible at running load and only show up when a calibration asks for a known change. On a scale that has never worked properly since installation, check the shipping stops first: a frame still carrying them can’t float. See why a Tecweigh won’t finish its zero or span.
Why does a resistance check pass a failing load cell?
Work on or near a conveyor, or inside an electrical enclosure, needs isolation under your site’s procedures and trained, authorised people. If that’s not you, stop and call us on 1300 101 666.
Because resistance only finds gross failures; the manuals call the millivolt output the best check of a cell’s condition. A drifting cell can hold a respectable resistance and still stop the scale holding a span. The live test is done on a powered scale card, with the belt isolated, while someone raises and lowers the calibration weight:
- Measure the excitation to the cell. On the current scale card it’s 5 V DC.
- Read the mV/V rating off the cell’s label. Most Tecweigh scales use 2 mV/V cells, but the label settles it.
- Record the signal with the weight raised, noting the polarity.
- Lower the weight and record it again.
- Confirm it rose, in the same direction, by a sensible margin.
Replace the cell if the signal is negative at any point, or above about 10 mV: 5 V into a 2 mV/V cell gives about 10 mV at most in normal running. A different rating means a different ceiling.
The older Australian WP20 manual tests by resistance only (more than about 10% from the expected reading for that cell model condemns it). Work only from that book and a degraded cell can pass and sit behind a drift complaint for a year. See why a belt weigher’s zero drifts and belt weigher load cells.
How do you find the bad cell on a two or four cell frame?
By elimination. Disconnect one cell at a time at the scale card and watch the load count and rate. If disconnecting a cell changes nothing, that cell or its cable was already contributing nothing. Confirm it with the millivolt test on that cell alone.
In our experience a bad cell is obvious on a two cell frame, because it takes the scale out. On a four cell frame the other three partly cover for a lazy one, so the scale still calibrates and repeats but reads wrong. If a four cell frame has an unexplained accuracy complaint, run the isolation test anyway.
What causes a load error you can find without a meter?
The manufacturer’s named causes on a load cell frame:
- a cell fitted with its arrow pointing up instead of down
- a cell wired against the colour code
- a damaged or broken cell wire, or a loose terminal strip or screw
- a physically damaged or overstressed cell
- material jammed near a cell
The first two are workmanship, and both survive a glance at a tidy frame. If the message started after someone worked on the scale, check them first. The older Australian WP20 book doesn’t list them; check them anyway. The WP25 adds a blown load cell fuse (not in scale card mode) and attached devices, such as a chart recorder, drawing more than 1 A in total. Surge and lightning also overstress cells: see protecting belt weigher electronics.
On displacement frames the list adds a misaligned LVDT, a broken or off centre spring, a stuck plunger and a pit worn in the deflection arm. Photograph a pitted arm: it explains a scale that has been getting worse for months. For the cable and junction box side, see is it the load cell, the cable or the junction box?
What has to go back the right way when a sensor is replaced?
On a load cell frame, everything goes back the way it came apart: the cell’s arrow pointing down, the spherical washers with contoured faces together and flat faces top and bottom, and every shim cleaned and refitted. A shipping bracket removed for the work stays out.
A replacement LVDT has to be aligned and the scale recalibrated. Keep its wiring clear of the deflection arm. LVDTs allow a wider resistance spread than load cells, so the load cell rule condemns good LVDTs.
Recalibrate after any sensor change and record the as-left figures, including the excitation and signal readings. Two readings a year apart show a cell going long before it fails, so we keep them in AIMM, our asset management system.
We supply parts for Tecweigh and the other major belt weigher brands: a genuine part where it’s available, or a suitable alternative, with compatibility confirmed and the part identified on the quote.
Does the control room know about it?
Not always. The Australian WP20 manual has no fault output among its relay functions. The US WP20 edition and the WP50 have an error function that operates on a scale data error, a load error or low power, so check what’s set up on your unit. Without it, the message can sit in a field enclosure while the rate and total look normal in the control room. See getting Tecweigh WP50 faults into the PLC.
The manuals don’t say the scale stops totalising during a load error. Treat every total recorded while it showed as suspect until the sensing is proved and the scale recalibrated, and reconcile against a weighbridge if you have one. See why a belt weigher doesn’t match the weighbridge.
Need a manual for your equipment?
A Tecweigh scale has a processor manual and a separate frame manual, and the sensor tests are in the processor manual. Note the processor model, the frame plate (load cell or displacement frame) and the load cell label, because the test and the expected figures change with all three.
Talk to us about manuals for your equipment. Send the make, model, serial number and software version (a photo of the label is fine) and we’ll help you find the right document.
When should you call us rather than swap another cell?
Call when the message survives the free checks (orientation, wiring, terminals, jammed material), when the load count won’t respond at all, or when the message comes and goes. Intermittent usually means a cable, a terminal or moisture, and a part swap that lands in a quiet week looks like a fix when it isn’t. If a cell has failed, we’ll tell you straight whether to repair it or replace it. Call 1300 101 666 or email admin@accurateindustries.com.au. See what happens during a calibration visit.
Frequently asked questions
Is load out of range the same thing as load error?
Yes. It’s the same condition in WP50 wording. The WP50 also tells you whether the signal went negative or too high, which points at wiring or at an overloaded cell.
Can a load error be cleared without replacing a load cell?
Often. Jammed material, a loose terminal, a damaged wire, a cell fitted upside down or wired to the wrong colours don’t need a new cell. Prove the cell with the millivolt test before buying one.
Does a load error mean our tonnes are wrong?
Assume so until the sensing is proved. Treat the totals from while it showed as suspect and reconcile them once the scale is right.