Allegiance 14 runs for 1-1.5 sec, stops for 3 secs, repeats

[N1755L]

Firstly, I'd like to offer a big Thank You to the individuals on here taking time to help others.

As the topic subject suggests, the unit starts and stops continuously, see here:  https://drive.google.com/open?id=1uJ6uensWvjAZgUGwVstodFVYk6ZrcFum

The background noise is the @#$@#&^&$$@ neighbour's A/C unit, I would have had to wait a long time to get a video without his background noise, but had to leave, so no time to get a better video.

It was working just fine last year, but now, when I switched the thermostat from Heat to Cool, walked outside, and saw what is on this video.  I of course switched the thermostat to Off.

Any suggestions as to what might be causing the unit to operate this way would be appreciated.  It doesn't sound like it's a problem with the start caps, sounds more like at the compressor?  Sounds as though it's firing up, but then, turns off 'cause of coolant problem?  Don't understand these systems enough to make a proper educated guess.

Thanks again.

[N1755L]

11 hours ago, N1755L said:

Firstly, I'd like to offer a big Thank You to the individuals on here taking time to help others.

As the topic subject suggests, the unit starts and stops continuously, see here:  https://drive.google.com/open?id=1uJ6uensWvjAZgUGwVstodFVYk6ZrcFum

The background noise is the @#$@#&^&$$@ neighbour's A/C unit, I would have had to wait a long time to get a video without his background noise, but had to leave, so no time to get a better video.

It was working just fine last year, but now, when I switched the thermostat from Heat to Cool, walked outside, and saw what is on this video.  I of course switched the thermostat to Off.

Any suggestions as to what might be causing the unit to operate this way would be appreciated.  It doesn't sound like it's a problem with the start caps, sounds more like at the compressor?  Sounds as though it's firing up, but then, turns off 'cause of coolant problem?  Don't understand these systems enough to make a proper educated guess.

Thanks again.

Alright, so let me put in the likely solution to this issue, in case someone later looks up a similar problem for their unit.

I had a technician over this afternoon, and so of course, the unit was working perfectly, as it's supposed to.  We tried turning it on and off and were never able to get the unit to misbehave the way it did previously.  Since there was nothing wrong with the unit, the only thing we could do is check the wiring, since the contactor on the unit seemed to be working flawlessly, the likely reason it would have been cycling as described would be as a result of a loss of the 24 volts to the contactor outside on the condenser unit (not sure if that's the right term/name for the unit, but basically, the same unit you see in the video above).

So why would there have been a loss of voltage to the contactor, and why was it not happening now?  Well since it wouldn't misbehave, what we did was re-do the Marrette joints (wire connector joints) at the unit, to make certain there wasn't a bad joint (when we took them apart, there was no evidence of damaged wires, or one of the wires slipping below the other when the Marrette -- wire connector -- was twisted onto the wires).   Next I checked and pulled and bent the low-voltage cable coming from the furnace to the outside A/C unit, just in case the cable had got damaged somewhere, either when originally being pulled, or maybe later, squirrels or rats chewing on it somewhere?  Cable all good, no sign of damage, and while pulling and bending it all along its length, never did the A/C unit ever cut out.  Doesn't appear to be a cable problem in any way.

Then all the connections and joints were checked at the furnace, because the furnace is part of the circuit, and the furnace is actually the originating source of the 120-24V transformer.  All was good at the furnace.

Then we went up to the thermostat, undid all of the wires to the thermostat, cut off 1/4 inch, stripped the wires anew, and reconnected them to the thermostat's terminal block.  But even before we got to this point, the technician had already asked about batteries in the thermostat, so he'd already suspected the thermostat, but this reconnecting of the wires was just a precautionary measure, since we'd as yet not found any smoking gun to indicate what the source of the cycling problem could have been.

So in the end, we never found the problem, but the thing that seems to be the only problem possible, is weak batteries in the thermostat.

In order to avoid potential problems as we've experienced here, I would suggest to everyone reading this to change their thermostat batteries every year (this is not my house, it's the wife's father's house, he's now passed away, so we had no idea that the thermostat had batteries, and we don't know how often he would have been changing the batteries), for the cost of a few dollars for two AA batteries, not worth the aggravation of potentially having the A/C or the heating malfunctioning.

While there's not way for me to say for certain, 100%, that it was a battery problem, it makes sense that it would have been the culprit.  We measured the voltage of the old batteries with the technician's multimeter, but these meters are calibrated for a certain percentage of accuracy more around the 100+ Volts range, not at lower ranges like 1 or so Volts, so the 1.3 Volts that we read with the multimeter could, given the error percentage, the actual voltage could have been more at around 1.2, or even 1.1 Volts?

I hadn't noticed it before, but after we installed new batteries in the thermostat and I switched it to On, I faintly heard a relay kick in, inside the thermostat.  So now the cycling makes sense, if the battery voltage was such that it was barely strong enough to activate the relay, and don't forget, it's not only a matter of activating the relay, it's not like only a signal being sent to the relay, when the relay is engaged, the batteries then have to continually hold that relay closed, the relay coil sucks up current, Amperage, in order to maintain that relay, in order to keep it closed. 

So again, if the batteries were only just barely strong enough to engage the relay, then after a second, the relay opens because there is not enough current in the coil for the relay to fight the pull of the spring, so the relay opens, and then the batteries, for those 3 seconds that the coil is disengaged, generates just enough charge to trigger the relay again, for another cycle of On and Off.

It seems to be the only thing that makes sense, that would explain the symptoms of that 1 second On and 3 seconds Off cycle.

That's my best guess, hope it can be of help to someone.

In case I'm wrong, and something else is found to have been the cause/source of the problem, I'll come back immediately and edit this reply.  Furthermore, let's say, in three months, I'll come back here to report that so far the A/C unit is working normally (if it still is), so that anyone experiencing a similar issue can get confirmation that this solution still stands as the likely reason for the problem as described.

And if you've read this far, I am open to suggestions from any technician who suspects another possible reason for the symptoms experienced here.  Thanks again.