Photo eyes & sensors

How does a garage door actually hold its own weight?

A garage door is not lifted by the opener — it is lifted by the spring, and the opener only guides it. A residential door weighs 85 to 400 pounds, and the counterbalance holds that weight so the motor only has to overcome friction. That is why springs and cables are professional work while sensors and remotes are not: one group holds the stored energy and the other does not.

Garage door safety covers the balance test and what an unbalanced door does to an opener.

How do I confirm the photo eyes are the problem?

Hold the wall button down continuously. If the door closes while you hold it and refuses to close any other way, the photo eyes are the fault and the opener is fine — most openers allow a constant-pressure close specifically so you can make that distinction.

Then read the indicator lights. Under 16 CFR 1211.10(a)(5) any alignment-dependent sensor must carry a means of showing proper alignment, which is what those small LEDs are. A steady light on both units usually means they are seeing each other. A flickering, dim or dark light on the receiving side usually means they are not. Which colour means which varies by manufacturer, so check the sticker on the bracket rather than a general rule.

Three causes account for most of it: a lens filmed over with dust or a cobweb, a bracket knocked out of line by a bike or a bin, and late afternoon sun landing directly in the receiving eye. All three are free to rule out and take under five minutes.

If the lights are steady and clean and the door still will not close, stop looking at the sensors. Watch when it reverses: a door that reverses after touching the floor is usually a travel limit, not a beam.

What does federal law actually require here?

Every residential opener manufactured since January 1, 1993 for US sale must meet 16 CFR 1211: a closing door must begin reversing within 2 seconds of hitting an obstruction, a second independent protection system must exist, and the manual release must be red. §1211.16(b) also fixes the exact words your manual carries — among them “Have a qualified service person make repairs to cables, spring assemblies and other hardware.” — which is why this page's verdict is not our opinion.

What UL 325 and 16 CFR 1211 require covers the full standard.

What is the one-minute test everyone should be doing?

The reversal test, monthly, with a 2x4 laid flat in the door's path: it must reverse on contact. If it does not, stop using the opener until it is adjusted, repaired or replaced. It matters because this system fails silently — a door whose reversal has stopped working looks and sounds exactly like one that still does. CPSC recommends inspecting the door and opener every 30 days.

Children, pets and the garage door covers why the standard exists.

At what point should I stop and call someone?

• The door is very heavy by hand with the opener disconnected. The counterbalance has failed.
• You can see a gap in the spring coil, or a cable that is frayed, slack, or off its drum.
• The door sits crooked, higher on one side, or has come off its track. It is still under full tension.
• The door does not reverse on the board test. The entrapment protection is not working.

None of those is calling too early, and the rule worth teaching at home comes from that same federal text: “NEVER GO UNDER A STOPPED PARTIALLY OPEN DOOR.”

Questions that come up next

Does a door that reverses mean something is broken?

No — the opposite. A door that stops and goes back up when it touches something is the entrapment protection doing exactly what 16 CFR 1211 requires. The fault worth investigating is a door that fails to reverse.

Can I disable the photo eyes to get the door closed?

No. That removes the external entrapment protection required since 1993, and it is the protection that exists because of the CPSC child fatality record. If a sensor is genuinely faulty, replace it — it is among the cheapest parts on the door.

Is it safe to use the emergency release with the door open?

The federally required manual text says to use it only when the door is closed wherever possible, because weak or broken springs may allow the door to fall rapidly. A great deal of DIY content advises the opposite.

Should I replace one spring or both?

If the door has two, quote both. The second is the same age and has taken the same number of cycles, so it is next. This is one of the few upsells in the trade that is genuinely honest.