Automatic Door Keeps Reopening or Stops Halfway? 9 Causes

An automatic door has a harder job than it looks. It has to open for someone approaching, stay open while they pass, close without touching anyone, and stop instantly if it meets resistance. When one of those judgements goes wrong, the door does something visible and annoying: it reopens for nobody, it stops halfway across the opening, or it swings too far and bangs into the floor stop.

Almost none of those are a dead operator. In Saskatoon and Regina the fault is usually a sensor seeing something it should not, or a door that has quietly become hard to move. The operator is doing exactly what it was designed to do — it is just being told the wrong thing.

Here are the nine causes we find, roughly in the order we check them.

First, which kind of door is it?

The answer changes with the type, so identify it before anything else:

• Low-energy swing operator. Opens slowly and with limited force, usually triggered by a push plate, a wave sensor or an access reader. This is the standard accessible entrance at an office, clinic, school or washroom.
• Full-energy swing or sliding door. Moves faster, so it needs overhead motion and presence sensors watching the opening the whole time. This is the grocery-store and lobby entrance.
• A manual door with a closer, that people call automatic. It is not powered at all. If yours has no push plate and no sensor, the problems in our post on why a commercial door is hard to open are the ones to read.

Our automatic door operators page covers what each type is used for.

1. A sensor is seeing something that is not there

This is the most common cause by a wide margin, and it is the reason a door reopens with nobody near it.

Motion and presence sensors respond to movement and to changes in what they see. Any of these will set one off: a hanging sign or banner moving in the draft from the door itself, a plant, a flag, a mat edge that has curled up, a floor buffer left parked in the opening, heavy rain, and — the Saskatchewan speciality — blowing snow crossing the sensor field.

Reflections do it too. A wet floor, fresh polish, a glass display case or a parked vehicle’s windscreen can bounce a beam back into the sensor. Low winter sun through a south-facing entrance is bright enough to confuse some infrared sensors outright.

Move the object, and the door usually settles down the same day.

2. The sensor is dirty, fogged or knocked out of aim

Sensor heads live on the header, where they collect dust, salt spray and cobwebs, and where a ladder or a delivery cart eventually clips one. A sensor that has been nudged a few degrees now covers the wrong patch of floor: too much of the approach, so it triggers on passers-by, or too little of the doorway, so the door starts closing on someone still in it.

On sliding doors, the door-mounted presence sensors ride with the panel and take the most abuse. Condensation inside a lens is also common on a cold entrance and looks exactly like a failed sensor.

Cleaning and re-aiming are routine. Re-ranging — telling the sensor how far out to look — is the part that needs the setup tool.

3. The door has become hard to move, and the operator reads that as a person

This is the cause behind most doors that stop halfway, and it is the one building owners rarely guess.

An operator monitors how much force the door is taking. If the door meets more resistance than expected, the operator assumes a person is in the way and stops or reverses. That is the safety system working correctly. The problem is that a dragging sweep, a sagging hinge, a binding latch, a stiff closer or debris in a slider track all feel identical to a person.

So the fault is often not in the operator at all. It is in the door, and it has usually been building for months. We check the door by hand with the operator disconnected first, for exactly this reason: if it is heavy to swing by hand, no amount of adjusting the operator will fix it honestly. The same underlying problems show up in why a commercial door will not close or latch, and the hinges, sweeps and closers behind them are ordinary door hardware service.

4. Cold

Winter makes cause 3 worse on a schedule. Fluid in the closer and the operator thickens, weatherstripping goes stiff and grabs, snow and grit compact into a slider track or a floor guide, and frost heave lifts a threshold into the bottom of the door.

A door that worked all summer at one force setting now needs noticeably more, and the operator starts reading normal winter drag as an obstruction. This is why we suggest a seasonal check here rather than a purely annual one — the same door genuinely behaves differently at −30 than it did in July. Our winter-proofing guide for commercial doors covers the rest of the entrance.

5. The operator has lost its learned settings

Operators learn their door during a setup cycle: where the open position is, how fast to move, how much force is normal. That profile lives in the controller.

A power outage, a brownout, a replaced board or a well-meaning reset can wipe or corrupt it. The door then opens too far, stops short, moves at the wrong speed, or hunts. If the misbehaviour started abruptly on a particular day rather than creeping in, ask what happened to the power that day.

Re-running setup is quick work, but it has to be done to the door as it is now, which is why we fix any mechanical drag first.

6. Something keeps activating it

If the door cycles open again and again with nobody there, and the sensors check out, follow the activation devices instead.

A push plate with a stuck or water-damaged switch holds the circuit closed and the door never gets to rest. Wireless push plates and fobs have batteries, and a dying transmitter can chatter. Damaged wiring in a bollard, where a snowplough or a shopping cart has caught it, will short intermittently in the cold and come good in the warmth. An access reader wired to the operator can also release repeatedly if its own power is unstable.

7. The opening limit is wrong, or the floor stop has moved

A swing door that bangs into the floor stop at the end of every cycle is either opening further than it should, or the stop has been moved, loosened or removed.

Do not leave this one. Every cycle is a hard impact through the arm and into the operator’s gearbox, and it will eventually cost an operator rather than a stop. If someone has taken the stop out because it was a trip hazard, the opening limit has to be reset to match, not simply left.

8. Wind and building air pressure

Saskatchewan wind and stack effect in a tall or tightly sealed building both push on a door with real force. On an exposed entrance the operator can be fighting a pressure difference the whole way open, which it may read as an obstruction, or being helped so hard on the way closed that it overshoots.

Vestibules exist largely for this reason. Where there is no vestibule, this becomes a setup problem: the door has to be tuned for the conditions it actually faces, not the ones in the manual.

9. Mechanical wear

Last on the list because it is the least common, but real: worn rollers and a scored track on a slider, a loose or bent arm on a swing door, a slipping belt, worn bushings in the operator itself. These usually announce themselves with noise and with behaviour that is rough rather than random.

At this point the question becomes repair or replace, and it turns on parts availability and the age of the unit — the same trade-off as elsewhere on the building, discussed in rekey or replace for locks. Current operators are on our automatic door operators product page.

What not to do

• Do not tape, cover or unplug a safety sensor. It is the reason the door is allowed to move near people.
• Do not force a powered door open or closed by hand repeatedly. Some operators have a manual or break-out mode and many do not, and you can damage the gearbox.
• Do not leave the operator switched off as a workaround. If the door is the accessible entrance, switching it off closes that entrance for the people who need it most, and the door usually has no closer strong enough to work well on its own.
• Do not keep cycling the power hoping it clears. If a fault clears on a power cycle and returns, that is information for the technician — tell them, rather than hiding it.

When to call

Book service when the door reopens or reverses without a reason you can see, when it stops partway, when it hits the stop hard, or when it has started needing a shove. Tell us the door type, when it started, and whether it is worse in the cold — that trio decides what we bring.

We service automatic operators, closers and the doors underneath them across Saskatoon, Regina and the surrounding Saskatchewan communities. If the entrance is the accessible one for your building, treat it as a priority repair rather than a maintenance item. Contact us or book a service call.