Failure rate of window / door magnetic sensors

Yes, that is a common occurrence with lightning strikes. Go ahead and replace all the contacts. You will find that all the contacts that share the same zone are all damaged. Yet other isolated zones are fine. This all depends on the path the lightning strike took.

Jim Rojas

snipped-for-privacy@hboi.edu wrote:

Funny we were just having a discussion about that here. According to one gentleman posting here, all of your contacts should be bad, but I see you report different contacts failing with different modes of failure. That what I typically see after a lightning strike. The simple explanation is that the contacts stuck closed were heated during the lightning strike event enough to "weld" the metal in the reed switch in the contact together. The dangerous cheapskate solution is to take the battery from the alarm panel, hook it to the contact for a second or two, and rap the contact with the end of a screwdriver. That is reheating the contact and unfreezing the "weld". This is the repair technique of the dreaded trunk slammer and should never be done in my opinion. The others that were burnt "open" when the reed switch was damaged to the point where there was no current flow possible anymore. If you have a meter I would check each switch by itself, even the ones that seem to work properly. If you find a switch showing anything greater than one (1) Ohm I would consider it suspect and replace it along with the rest of the bad contacts.

sounds like you might have a grounding problem.

It happens, usually it welds the switches closed, which is why we always recommend the homeowner test all openings at least once a year but definitely after a major lightning storm nearby. I've never found one go open though.

Thanks for all the replies. I did go around and check each switch with a meter. And I ordered all new contacts - about $150 worth.

As for a grounding problem, I have the control panel grounded to the ground rod out by my meter. This was a pretty bad strike, as I lost lots of things. The control panel had two traces actually melted on zones 5 and 6. I jumpered over them to repair that. No fuses blew????

Anyway, thanks again for the quick replies.

snipped-for-privacy@hboi.edu wrote in news:1191252145.605749.66590 @d55g2000hsg.googlegroups.com:

You should still replace the control board. You never know what might be fried in the electronics, even if the panel seems to work correctly.

A replacement control panel is not very expensive.

What kind of panel is it?

All contacts on the affected loop were ruined. One froze open the rest froze closed. Replace them all. Magnetic contacts are cheap.

I've seen them go open or closed (mostly closed). We usually replaced everything on the affected loop. Since I always ran motion and glass breaks on individual zones it only affected the cost of replacing a few extra contacts.

It will be if he gets it from the same source as the contacts.

I made a mistake on my total. I only spent $90 on contacts. The mini stick on cost about $3 each, the door ones are $5-6. The other $60 was from an irrigation timer I also bought that was blown.

The control panel is an old Radio Shack but works for our needs. I've checked out all the curcuits and the unit is fine. But if I need to replace it, I'll be posting on here for suggestions.

A bit OT, but has anyone found the wireless systems reliable? I originally installed an X-10 wireless system, but it kept going off from stray signals or would continually report sensors that did not respond. It was a big PITA. I have had no problems with the wired system for 8 years until this lightning strike.

I'd say a single $90 repair in 8 years isn't doing too badly... you'd probably spend more than that on batteries for a wireless system in that time.

Granted, welding shut seems to be the more common failure mode. But sometimes, they do go open. I think what happens is that the heat causes the glass tube to crack where the metal reed goes through the glass, causing it to lose its support and the spring tension that tends to keep the switch closed. Back in the old days, some manufacturers used gold to plate the contacts of their reed switches. Bad idea.

Actually your quite correct...I do remember one house that none of the switches worked about a week after I put them it...after calming down a pissed off client, come to find out ADT installer was there "testing" all of my switches with a 12v 7amp battery and a siren. Duh. Homeowner wanted me to replace all the switches...idiot. Told him sorry...outta warranty have ADT fix what the exploded. He just smoked dem contacts till they blew open and stayed open.

musta been some wimpy contacts. :) shoulda used a piezo. ;)

Why did the client have ADT come in? Sounds like the customer got taken in by ADT.

They were Sentrols.

Yep. The problem was it was a builder system and ADT can hit the homeowners faster than we could even though we were the builder's low voltage contractor. ADT get's info from closing reports, we can't afford that...and somehow they were also getting phone numbers before they were even listed...dunno how, maybe they bribed the sales people.

On this particular one it didn't matter, because after all the brew-ha-ha blew over the homeowner realized what idiots they were and I got the sale anyway. ADT never got to install anything...because they weren't "allowed to" ! According to them WE were suppposed to go and fix it before they would install (the homeowner thought this was dumb too). If they were smart they would have installed their equipment and waited a couple of days to go back and fix the switches, but they didn't...so we got it.

I've got an old kids walkie talkie set that has a button on it to send morse code. I have shorted the button so it sends the tone all the time. I put 2 alligator clips on one side of the battery lead. I use it sometimes to test switches. Basically I run the 9v battery on the transmitter through the alarm circuit. As I open and close windows the receiver beeps when loop is closed and is silent when loop is open. Don't use it much but every now and then is comes in handy on someone else prewire.