I have 5 detectors in the house: 1 in the basement, 1 in the MBR on the first floor, and 3 upstairs in the bedroom.

The detector in the basemet has a Green LED on. I am assuming it is the first detector in that circuit coming from the breaker box.

Inside the basement detector are 4 other wires nutted together -- the basement lights are wired on the same circuit.

What is odd is that the other 4 detectors do not have the green led on. Additionally, when I test the one in the basement, none of the other ones go off.

When I test one upstairs, the others do go off, except for the basement.

When I swap detectors between locations, regardless of which one I put where, the basement location has a green led, and the upstairs do not (and they are the same models).

Is it safe to assume that the 4 other detectors are not getting 110V power, are running off battery, but still can talk because their interconnect wire is working?

So, to fix this, is my best guess to re-nut the connections in the basement detector, with the hope that something is loose in the 14/3 wire that sends it up to the rest of the house?

If the connections are secure in that detector, and that is not the problem, what else could be causing this?

Thanks in advance!

Your diagnosis of the condition and solution is exactly correct.

If the wiring is not loose ,then you will need trace out the wiring looking for a miswire.

Ughh... well, in the process of wiring in 2 new detectors in the basement, I retied everything together in the 1st detector in the series.

My 2 new ones that branch of the 1st one work fine -- green LED.

However, the rest of the house is still not powered :(

Next step: hope that one of the connections at the other ones is lose, thus killing the circuit. However, for that to be the case, it could only happen at the next one in the series, right?

My biggest fear is that I am going to reconnect at the connections, and they still will not work.