Help troubleshoot my phone jack replacement

June 2, 2004 7:58 PM

I'm replacing a phone jack. Or rather, I'm trying to replace one. I've done same before, but this time I can't get it working and I think some troubleshooting is required. There are more details, and too many wires, inside.

First off, this particular jack didn't work when I bought my condo three years ago. I removed the old jack sometime back and have made periodic attempts to install a new plate and get it working, with the help of Google. The problem could therefore simply be improper installation or something more serious for which I will need a technician.

About the installation. Now, I know there are usually four wires in a phone jack, that they should be matched to the corresponding coloured wires on the plate, and that the red and green wires usually "do the work". But in this case there are two sets of four wires, and the two green wires and two red wires are spliced together in two little plastic thingies. Could this be why I can't get it working? If not, how should I hook up the plate given that I have two black wires and two yellow wires to work with?

posted by orange swan to computers & internet (5 comments total)

The non-functioning jack is evidently in the middle of a circuit, thus the additional wires are to serve the outlets further down the line. Your first troubleshooting then is to make sure all of the other circuits in the condo are working. If they are, then the problem is in the outlet you are working on; if not, then the wiring needs troubleshooting. You are correct that only two of the four wires are typically used in a phone circuit; the other two were originally used to deliver current for lighting the dial on early princess phones and such so are usually unused with modern equipment. This is not always true, however; before I had cable out here in the boondocks I got a second line for my dialup internet, and the installer used the second set of wires rather than running new wiring through my house. From your description, it seems that undoing the splice on the red and green wires (plastic thingies=wire nuts?) and tapping in there should work. If not, this google search gives a lot of info.
posted by TedW at 8:47 PM on June 2, 2004

The inside pair carry your primary line. You can see the colours in the phone plug. I don't believe it matters which way 'round the pair go, but if it does, simple enough to flip 'em.

You can tie the same-colour wires together if this is a middle box.

So if it's white-green/white-red as the middle pair in the phone plug, connect those colours to the yellow and black tie-down.

IMO&IME, YMMV.
posted by five fresh fish at 11:02 PM on June 2, 2004

There's various ways of wiring things. The easiest to deal with would be "home run" where everything goes back to a punchdown block or the telco point of presence. If you have access to the floor's/building's telephone closet, if there is one, you could see if that's likely. Other wise the various jacks in your apartment are probably inter-connected in some more hidden fashion in junction boxes that may now be buried behind drywall.

Multiple pairs are there as spares, in case one goes bad, or for second (or more) phone lines, extra bells etc. I think most modern cabling tends to be CAT3/5 four pair, just like computer cabling, older cabling may have fewer pairs. Princess phones did indeed use one of the pairs for dial/button lighting, though often with a brick power supply and a special jack adapter, so there is unlikely to be low voltage lighting power on any of the wires. Old touch-tone phones (Princesses etc.) care about polarity, but pulse dial and modern phones don't mind if you get it backwards.

My first suggestion would be to try all the pairs to see if there is dial tone on any of them. You don't need to attach them to do this, just touch them each in turn to the terminals attached to the middle pair on the jack. After that check out the wiring closet/POP as there may be another pair that could be connected and work.

If none of this gets you any further, there are tone generators used for tracing cabling (an example -- not an endorsement just the first I found when doing a search, you should probably shop around). You attach it to a pair in the cable in question to trace it back to its source (if there is one and it doesn't just stop somewhere in the middle of a wall), or use it to identify unlabeled pairs at a punchdown block.

I'm not a cabling expert, but I have dealt with quite a lot of voice and data cabling one way and another, including pretty much the same situation that you are describing: I was adding a second line in a condo built in the 70s. I got most jacks to work after a little poking around, but there was one I could never find the connection to.

Don't forget there are wireless phone jacks for about the same price or less than the tone generator -- they definitely have draw backs, but they would be easier than hacking through drywall, or paying someone to pull new cable.
posted by Quinbus Flestrin at 11:35 PM on June 2, 2004

I'm happy to report that the phone jack is working now and it was actually pretty simple!

I took TedW's advice and snipped off the plastic thingies/wire nuts. I then spent awhile experimenting with wire connection. Turned out that the second set of coloured wires worked when connected to the jack plate.

Thanks all - you've saved me the bother and expense of hiring someone to install the plate. And when I called around the lowest estimate was $50.
posted by orange swan at 6:46 AM on June 3, 2004

I'm going to add a postscript here, just for the sake of having a complete solution.

A few days later I discovered that the phone jack in the next room wasn't working. Then I thought, hmm, it did work when the other phone jack had its red and green wires spliced together. Perhaps it would work again if I restored those connections, while maintaining the connections to the new plate. So I took off the plate and connected the second set of red and green wires to the red and green wires already wired to the plate.

Bingo. Both jacks are working now.
posted by orange swan at 4:05 AM on June 5, 2004