Hey All,

So about a week ago the power company came out to update our power meter, they shut off all power to the house for about 10-15 minutes, then supplied power to the house again. Well... Somehow, wether it was because of the power cycle or not, my a/c stopped working. I checked the fuse panel, good. Checked the switch in the basement attached to the furnace and blower and it was also on. I checked th compressor contactor and it seemed good. The a/c kicks on when a manually push down the contactor, but doesn't stay on when it go. (Don't try this at home) I taped the push button down to keep the a/c on, went to check the blower and it is still not running, no air supplied to the vents. I figured it could be the contactor so I ordered a new one, just installed it today (thanks to some pros on the DIY forums) and I am still getting the same results. So now I'm convinced it's not an issue with the contactor, it may be something more in depth. Does anyone out there have an idea of why I can get the a/c unit to turn on by pushing the button on the contactor, but why the blower and even the furnace seem to have no power supplied to them? I've tried everything that I know so far(not much) PLEASE HELP! Thanks-

 

First thing you should check is why the 24V is gone (that is why you have to tape the contactor button to get it started), so need to check if the transformer is still good and is still generate 24V ?.

 

Welcome to the forums.

Is this a furnace with A/C or heat pump ?

Clocert's recommendation in checking for 24vac is your first priority. It's highly likely the turn on surge opened the primary winding of the transformer. Many furnaces have a control board located in the blower section that may have a protection fuse on it.

If you don't know where to look..... post the make and model of the air handler or furnace.

 

Clocert -I checked as far down the line for power as I "safely" know how to. I checked the wiring, traced it back to the panel, and checked the actual breaker in the panel. Where is the transformer I should be checking?

Pj -the furnace is with A/C and there is a computer board attached to the blower as well, although I don't see any obvious fuse to check.
It's a Rheem Classic 90.

Also, another thing to note if I didn't previously, also attached to the blower is an AirCycler panel, which when the little deadman switch is pushed in, will be powered and it's not either. Thanks again for the help fellas and bear with me, new home owner...

 

Not your household 110/120 power, there should be a small device (transformer) near your furnace blower or control board. It has 2 small wires which connected to your control board, contactor, and/or your Thermostat. Check these 2 small wires, they should have 24V, if not, then the transformer may be bad.

 

If you have trouble finding the transformer, another way to check for voltage is to remove the thermostat from it's mounting plate. With your voltmeter set to AC volts, put one probe on the R terminal of the thermostat mounting plate, and the other probe on the G or Y terminal. You should read 24VAC. If you do, your transformer is good.

 

Alrighty, so I checked the voltage off of the thermostat, and I am definitely getting 0v. So judging by your guys comments it may be the transformer. Is the transformer the gray cylinder type deal I see in with the blower? Also, there is a similar piece out attached to the a/c unit as well. Would they show anything obvious telling me they are bad?

 

PJ- the model # I see is RGRJ-06EMAES hopefully that's what you need to see if this type has a protection fuse?

 

Most likely you are looking at the capacitors. The transformer should look something like this.

 

Perfect, I just happened to pull that part out from inside the unit, the white and black wires are soldered goin into it, and I've got red and yellow wires also soldered going out of it. The black and white are showing 12vac going in, and red and yellow have 0 coming out. Should be as simple as replacing this transformer?

 

You want 120 vac between black and white.

 

Sorry that was a typo, yes I have 120vac between the black and white wires

 

Replacing a transformer is not difficult.
If you decide to get a universal 40 VA transformer the color code can be different.

Yellow and blue are usually the low voltage wires. Yellow is 24vac common.

Black and white are for 120 volts, tape off red and orange individually.

 

Great! Just ordered up the new part, hopefully will have some good news to post in about 2 days. Thanks for all the help