AC outside unit not working intermittently

[Codyboy]

Twice now the o/s unit failed to come on. Tstat is calling for AC but I'm not sure if inside unit is blowing.
We had turned the AC up higher to 74 and come home to 77 degrees.
Both times I can reset the breaker for both in and out and the o/s unit will come on.
I will try and duplicate it tomorrow or at least check it during the day to see if its on when it says its on.
It is a 3 zoned system and all Tstats are calling .

 

[mm08822]

Check outside contactor has 24v when tstat is calling and set to ac.
Inside blower should be running too with fan set to auto.

 

[Codyboy]

Ok. My wife says it wasn't blowing inside, but not sure thats correct.
I hate when things happen late and no time to troubleshoot it.
Hopefully it will do it again tomorrow and I can check some voltages inside and outside.
It appears that resetting the control board causes it to send the 24v to the o/s unit. Rebooting the system basically.
Not sure if there are any codes it would display or not.
Will check in the attic tomorrow.

 

[Buckaroo5]

My first thought would be capacitor. Check it visually to see if it is bloated and test capacitance if you have that capability on your multimeter. When it should be running, give the fan a nudge and see if that gets it spinning.

 

[danski0224]

it wasn't blowing inside

If the indoor fan is "on" and there is no air coming out of the registers, that's a sure sign of a frozen indoor coil.

 

[mm08822]

If the indoor fan is "on" and there is no air coming out of the registers, that's a sure sign of a frozen indoor coil.

And could be due initially to dirty air filters progressively diminishing air flow.

For certain that would initiate a freeze up.

 

[fitter30]

If blower isn't running the condenser is running would be iced up from the evaporator to the condenser. By resetting the breaker if the unit tripped off on a safety will reset the fault. Another way is to turn system to off then back to cooling or heat. By resetting unit system by breaker our there is a fault code it's probably gone.
Turn the fan switch in the on position to see if it stops.

 

[Codyboy]

Check outside contactor has 24v when tstat is calling and set to ac.
Inside blower should be running too with fan set to auto.

It finally acted up again today so I could do so.e troubleshooting.
Inside unit was running but outside was not.
Pulled the cover outside and had 240 volts but no 24 volts coming in.
Pulled the cover on the 3 zone controller and had 24v on all 3 Tstats as the were calIing.
Pulled the cover on inside unit and had 24 volts on the green plug in block from blue common to the yellow. Traced the wire and yep that is the wire going to the outside unit.
Hmmm. I have it inside but not outside.
Well hell, while fiddling with the wires and moving them around there was a nick in red and blew the 3 amp fuse. Ugg.
Finally found that type fuse in my 93 F150. It's a 10 amp but whatever. Taped up the nick, plugged it all back in and noticed the blue common was loose on the green block connector . 24 volts on the block/board but the common wasn't making it to the outside unit.
Reterminate it and seems to be working now.

 

[mm08822]

Good! Now go get a 3 amp fuse.

 

[fitter30]

You knew how and why the fuse blew. IF ever you fine a blown or bad fuse on a circuit board NEVER put in a larger fuse or type unless your ready to buy a new board and maybe other parts. Don't just buy one fuse leave one or more in the control cabinet.