Work in this order: check the power, check the safety sensors, check the emergency release trolley, then test the door balance by hand. That sequence separates the free fixes from the real repairs and tells you whether the problem is the opener or the door.
A garage door that will not open is either a five minute free fix or a four hundred dollar repair, and the difference is usually identifiable in about ten minutes.
Work through this in order. Do not skip ahead, because the later tests only mean something once the earlier ones have passed.
Step 1: does the opener have power?
- Is the opener light on, or does the wall button do anything at all? If nothing, this is electrical, not mechanical.
- Check the outlet the opener is plugged into. Many garage outlets are GFCI protected and a tripped GFCI is a very common cause.
- Check the breaker for the garage circuit.
- If the outlet is dead and the breaker is on, the GFCI may be on a different outlet elsewhere, sometimes in a bathroom or outdoors.
- If the opener has battery backup and the power is out, check the backup is charged and engaged.
Step 2: is it the safety sensors?
If the opener runs on the wall button when opening but refuses to close, and the opener light flashes or the unit beeps, this is the photo-eye safety sensors and it is the single most common garage door call there is. The two sensors sit near the floor on either side of the opening and they must see each other. Look at both indicator lights: both should be solid, and a flashing or dark light means that sensor is not aligned or not receiving. Wipe both lenses, because cobwebs and road grit genuinely cause this. Check nothing is in the beam, including a bin, a bike wheel, a coiled hose or a snow shovel leaning against the wall. Check neither bracket has been knocked by a car door. If a sensor has simply been nudged out of line, gently bend it back until both lights are solid. This costs nothing and fixes a large share of calls.
Step 3: is the trolley disconnected?
If the motor runs, you can hear it working, and the door does not move at all, pull on the emergency release cord and look at the trolley, which is the carriage the rail arm attaches to. If somebody pulled the release at some point, perhaps during a power cut, and never re-engaged it, the opener is running with nothing attached to the door. Re-engaging is usually a matter of pulling the cord toward the door, or in some models pushing the release lever back, and then running the opener once so the trolley re-latches. This is free and it is more common than people expect. If the motor runs and you hear grinding rather than smooth operation, the plastic drive gear has stripped instead, and that is a $180 to $320 repair.
Step 4: test the door itself
This is the test that tells you whether you have an opener problem or a door problem, and it is the one most people skip. With the door fully closed and the opener disconnected via the emergency release, lift the door by hand. A properly balanced door should lift with moderate effort, roughly the weight of a heavy suitcase, and should stay put when you stop it halfway. If it is extremely heavy, will not lift at all, or slams back down when released, the springs have failed and the opener was never the problem. Look above the door for a visible gap of an inch or two in the torsion spring coil, which confirms it. Do not keep pressing the opener button to force a door with a broken spring, because that is how you strip the opener gear and turn one repair into two.
What each outcome means
| Finding | Cause | Fix | Cost |
|---|---|---|---|
| Nothing at all, no lights | Power or GFCI | Reset outlet or breaker | Free |
| Opens but will not close, light flashing | Safety sensors | Align or clean | Free to $250 |
| Motor runs, door still | Trolley disconnected | Re-engage the release | Free |
| Motor runs, grinding noise | Stripped drive gear | Gear kit | $180 to $320 |
| Door very heavy by hand | Broken spring | Spring replacement | $350 to $550 |
| Visible gap in the spring coil | Broken spring, confirmed | Spring replacement | $350 to $550 |
| Door crooked in the opening | Broken cable | Cable replacement | $180 to $350 |
| Remote only fails, wall button fine | Battery, or LED interference | Battery or bulb swap | Free to $15 |
Ranges reflect typical Capital Region projects and are for planning only. Every Sundog quote is written, itemized, and free.
Frequently asked questions
Why will my garage door not close?
Almost always the photo-eye safety sensors near the floor. Check that both indicator lights are solid rather than flashing, wipe both lenses, and clear anything from the beam path. A sensor knocked out of alignment by a car door or a shovel is the usual cause and realigning it costs nothing.
The motor runs but the door does not move. What is wrong?
Either the emergency release trolley has been pulled and never re-engaged, which is free to fix, or the plastic drive gear has stripped, which you can normally hear as grinding. Check the trolley first because it costs nothing. A gear kit runs $180 to $320.
How do I know if my garage door spring is broken?
Disconnect the opener with the emergency release and lift the door by hand. A door with good springs lifts with moderate effort and stays put halfway. A door with a broken spring feels enormously heavy or will not lift at all. Then look above the door for a visible gap of an inch or two in the spring coil.
Should I keep pressing the button if the door will not open?
No. If the door is stuck because a spring has broken, repeatedly running the opener against the full weight of the door is how you also strip the opener gear. That turns one repair into two. Stop, disconnect the opener, and diagnose by hand.
My remote stopped working but the wall button is fine. Why?
Try the remote battery first, which is the most common cause. If that is not it, an underrated cause is LED bulbs: some emit radio interference that dramatically cuts remote range, so swapping the opener bulb for one rated for garage door openers sometimes fixes it outright.
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