Need Help, my magnetic reed switches are working in reverse.


Old 06-27-19, 02:17 PM
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Question Need Help, my magnetic reed switches are working in reverse.

Hello, I installed two french doors and replaced the magnetic reed switches. I used Honeywell 951WG-WH Stubby Recessed Magnetic Contact Switch from Amazon (Link)

For some unknown reason, one door is in the closed position with the door closed and the other is closed with the door open (they are the same but working in reverse).

I don't know much about this kind of stuff, but I bought the switches together in a three pack. So, shouldn't they both be the same (NC with door closed), right?????? Or have I made a mistake.

[another strange thing is the closed door won't work with it's supplied magnet, I needed to use a stronger magnet (I just assumed it was too far away.... tho, the door that has a closed circuit with the door open works with the supplied magnet... They are both installed the same]

SO CONFUSED!! Please help.

Thanks - Rick
Old 06-27-19, 03:52 PM
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Are they on the same zone? If so, do the pairs of wires run back from the doors back to the panel, and are combined inside the control box, or are the contacts tied together within the door frame.

This sounds more like a wiring error of some sort.

Are the doors metal/metal framed? That can affect how well the magnets work; and some magnets do vary in strength, even when new.
Old 06-27-19, 03:55 PM
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Okay....this might be a bit of a stretch, but I can think of a configuration of switches and magnets that might give you this symptom. Can you post a picture of how your switches & magnet sets are mounted, relative to each other?

I'm guessing that the two sets, on French doors, might be right next to each other---which can be a problem if not accounted for.

The "WG" in your reed switches' nomenclature stands for "Wide Gap," and Wide Gap switches can be tricky when it comes to the magnetic fields that open and close them.
First, they're polarity-sensitive, meaning they only have that wide make-or-break gap when they're "feeling" the right end (N or S) of their magnet. If the magnet field is reversed, they have a shorter-than-normal gap.
Second, and possibly more relevant here, if the two sets of switch/magnets are installed close to each other, the two magnetic fields can interact with each other by combining and possibly partially "collapsing" the combined field. In that circumstance, one switch may be in a strong enough field to close, while the other isn't.
If magnets are installed right next to each other, close enough that they can "feel" each other, then they should be _pushing_ at each other rather than pulling. Be aware that in this configuration, the magnets will weaken each other over time; but it can be used for a temporary fix.

But that's all conjecture until we can see how your switch/magnet pairs are installed. Can you post a picture?

In the meantime, open the doors wide to get the installed magnets out of the way, and play with two hand-held magnets to see what it takes to close up the doors. I'm assuming you have a Chime feature at your Keypad. Be sure to orient the magnets so that you're always pointing the same polarity (North or South) at each switch. Unless you have a faulty switch, I'm guessing you can simulate a closed set of doors with hand-held magnets. Then see if the magnets in the doors are oriented differently.

Hope that's clear. Let me know if it's confusing.
Old 06-28-19, 07:43 AM
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If the magnetic switches have both a NO (normally open) and NC (normally closed) terminal, move the wire from one terminal to the other on the door with the incorrect position indication.
Old 06-28-19, 05:46 PM
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@beelzebob: Check the first post. OP named a Honeywell 951WG-WH switch, which is a closed-loop switch: "NC" in alarm jargon.
Old 06-29-19, 03:42 PM
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Sounds like it's the wrong switch; OP has a Normally Closed switch and a Normally Open switch is needed. Don't forget that National Electrical Manufacturer's Association definitions are likely used. Normal is with no external forces acting on the switch; like a magnet. That's why you use to see "Normally Closed - Open Circuit" and "Normally Open - Closed Circuit".

With no magnet the switch is closed and when the magnet is brought close, the switch opens.
Old 06-29-19, 11:19 PM
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A 951WG-WH switch is a closed-loop switch: "NC" in alarm jargon.

RickDel has the right switches, as far as "NO/NC" is concerned. I don't think there's a pro on this forum that hasn't used a 951WG in a standard d/w protection loop at some time.

I can remember that back in the mid/late 70's, alarm techs were confused about what was "Normally Open" or "Normally Closed"---because most alarm techs never had any formal electronics training. Ademco and the rest of the alarm device manufacturing companies went back and forth (as I recall) briefly but settled on catering to technical ignorance and starting calling switches "normally closed" in _Alarm Jargon_ when they indicated a closed door/window, even though that nomenclature was, _for that kind of switch_, the opposite of standard Electronic/Electrical nomenclature.

In short, the alarm industry has its own jargon that's sometimes at odds with standard electronics designations, and sometimes it causes confusion--but we're stuck with it. "Normal" in Alarm Jargon means the state of a switch that puts a protection loop in a "Happy State" (No Alarm or Trouble condition) when doors & windows are all closed and there's no movement around motions and no smoke or heat anomalies around fire sensors, etc, etc...
Sometimes that "Normal' state agrees with standard electronic designation, and sometimes it doesn't.

So nearly all door and window sensors are NC in Alarm Jargon and NO in standard electronics nomenclature. On open loops like smoke & heat sensors, Alarm Jargon and standard electronics nomenclature happen to coincide.
2john02458 voted this post useful.

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