End Of Line (EOL) Resisters


Old 07-11-15, 08:12 PM
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Join Date: Jul 2015
Posts: 3
End Of Line (EOL) Resisters


I've recently purchased a home that was built back in 97. The house was hard wired by ATD when built. The previous home owner had been using a wireless and alarm and took all the equipment with him. What I'm left with in a large hole in the sheet rock with tones of wires. I've started to identify and rearrange the zones so far.

Why question is when I use my volt meter it seems I get a common reading of about 15ohms give or take. Is it safe to assume ADT 15k resistors at the EOL?

Next question, if that is the case with the 15k resistors will that limit me to the panel I can purchase for my install? I'd hate to have to go in in change out all the resistors. The installer used 3/8" contacts through out the house and their embedded in the bottom of the window frames with some sort of clean epoxy.

Any thoughts or opinions on the Honeywell Vista 21iP? In all I'll have about 19 hard wired zones.

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Old 07-11-15, 09:45 PM
Join Date: Jun 2011
Location: USA
Posts: 293
If you are reading 15 ohms and not 15,000 ohms then you do not have 15k ohm resistors.... I personally have never seen higher than 6k used for alarms.

Sounds like there are probably no resistors installed and what you are reading is the wire and contact resistance by itself.

If you have multiple windows in the same area, are they each wired with home run to where the panel will be? If so, you can combine some of these in series to have less zones. Possibly not need zone expander from the 8 on board with vista panel.

As far as hardwired panels, nearly all should be compatible. Vista21iP is an excellent panel to work with and fairly easy to program basics, plenty of advanced options. Just be sure to get an alpha keypad like 6160 or equivalent for programming. Even if you go with a fancier touchscreen pad, the 6160 is well worth the investment.
Old 07-12-15, 06:34 AM
Join Date: Oct 2008
Posts: 1,312
I suggest you get a package of assorted resistors at Radio Shack, then learn how to read them with your multimeter. Search google.com for the words Resistor Color Code.

Also read various lengths of wire which is not connected to anything.

Once you have a good understanding of resistance and readings you would typically get with a length of wire, then MUCH easier to read the wires in your house and understand what is probably going on with them.

Also some multimeters have a beeper on them or you can make a beeper - circuit complete, it beeps. Then connect to one wire, go around and open/close windows doors, when beeping stops, that is at least one thing that wire goes to - label it.

Sometimes there will be one separate wire to each door / window. Other times one wire may go to say all upstairs windows. Or all windows in a particular room.
Old 07-13-15, 10:09 PM
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Join Date: Jul 2015
Posts: 3
Thanks for the help fellas and I've learned to read my multi meter (as far as reading resistance anyway).

I've ran across one window that has a bad 3/8" contact. I'd open the window and my reading would go from 15 to 30-50. Never reading the same number twice but in that range. After digging the contact out of the aluminum window frame and working with bare wire everything is checking out now. I've got two other windows that have contacts and are wired but opening the windows does nothing on my multimeter. This is the upstairs zone and I'm positive I have the right daisy chain of wires.

Could this be two more bad contacts? I've traced the wires from the panel into the wall and then through the attic to where they are ran into the wall. Both wires look good from what I can see. These windows are on different sides of the house for the upstairs zone and everything in between is checking out.

One last question, what adhesive or epoxy should I use to secure 3/8" contacts back into the window from? There is some sort of clear adhesive used now that seems to seal really well.

Once again thanks for the help guys!
Old 07-13-15, 11:31 PM
Join Date: Jun 2011
Location: USA
Posts: 293
Are you 100% sure you have the correct wires? What you are describing is two zones for upstairs? Not sure I follow correctly... Could the wire you follow go to an outside phone box?
Just a thought.

Another thing you could try taking those contacts out and either connect the wire ends together and check with meter. Could determine bad contact. Connect a 9V battery to the wires and check voltage on other end to verify wire is correct. It could be possible to have a bad wire as well.

I suggest clear silicone caulking. Small squeeze tube if you can find one. Dont take much
Old 07-13-15, 11:55 PM
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It is possible to have multiple shorted contacts especially if there was any nearby lightning.

What you are doing would be a cake job of you had a tone generator and tracer.

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