HVAC help

[Reit38]

This winter I moves my thermostat and ran new wire to the furnace. Didnt have a problem all winter. . . Now we are to AC we have a problem and Air conditioner wont run. Worked fine before I reran wire. Assuming I'm missing something obvious



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[mrobins297aaa]

with the thermostat set on cooling see if you have 24 volt between Y and C at the furnace, if you do check the 240 volt fuses at the disconnect outside

the wiring looks correct

 

[Reit38]

Well scratch that I switched it over to heat and thats not working either
We ran the heat not me then 2 weeks ago and worked fine then



I have fan set to 'on' and that is not doing anything.
I can hear a slight hum from furnace that I always hear

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[mrobins297aaa]

did you check the switch on the side of the furnace? is it on?
do you have the blower door off? furnace won't run with that off

 

[Reit38]

Switch is on


I held in safety switch on blower door when I had the door off

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[mrobins297aaa]

well see if you have 24 volts between r and c (with the switch closed)

 

[Reit38]

Showing 0 as far as I can tell

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[mrobins297aaa]

the 120 volt breaker isn't off in the panel is it?
if your not sure on the 24 v hold a jumper between r and g and see if the blower starts (door switch closed)

 

[Reit38]

Nope. I even flipped it off and back on to make sure

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[Reit38]

Use jumper on R & G . . . Or R & C

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[acmikee]

jumper on R & G will bring on the fan.....R & C will blow the fuse or transformer
with 0v at R & C your fuse or trans is blown or you don't have 120V
check your fuse and your line voltage

 

[The Cobbler]

can't comment on the problem , but I sure would shorten up those long stripped wires going into the terminal block.

 

[Jim greengo]

C&eck the 3a fuse on board in furnace

 

[Reit38]

Not getting anything with the jumper wire

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[mrobins297aaa]

check the 3a fuse as Jim said, if it's good than check to make sure you have 120v to the transformer/board if you have 120v to the transformer than you need to replace the transformer.

edit, if you have 120v to the transformer before you get another transformer make sure you don't have 24v on the other side of the transformer because I guess the transformer could be good and something is wrong with the board.

 

[bonneyman]

Sure sounds like a wire is broken somewhere - or maybe one of the wire connecting posts on the board has a cold solder joint?

Jump R to G on the furnace control board. Blower should come on. Tell us what happens.

 

[Reit38]

3amp fuse was blown. Got to run to town to get a new one.... what would cause it to blow

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[brewchief]

Look at the wire going to the A/C very carefully, sometimes critters will chew them outside and the will short out. Bad contactor is also a possibility but not as likely. I would verify the wires condition before replacing the fuse and powering it up.

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[Reit38]

Replaced the 3amp fuse. Blower kicked on, furnace kicked on. AC did nothing when I switched over to cooling.

I ran jumper after that from r and g and blew the 3amp fuse again

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[mrobins297aaa]

are you sure your not jumping r to c?,

Did you ever check the 240 disconnect outside to see if you have fuses in there and that they are good? It's possible that the ac didn't come on after you changed the 3a fused because you may have a blown 240 fuse outside by the unit.

How about trying this , check for fuses outside, do like brewchief said and take a close look at that 2 wire going to the ac unit outside.

if you don't find any problems then

don't jumper anymore wires, disconnect the two wires (y and c) at the furnace coming from the ac unit and just see if you can get the heat to work properly.

then we can go from there


I hope you bought a box of fuses

 

[Jim greengo]

Are there any splices in the wire between stat and furnace in the basement?
I wonder if the greens are spliced someplace above the furnace and they got switched up.
You could have the common from ac running up to the g on stat.

 

[acmikee]

disconnect the red wire on the Y. replace the fuse and turn on the ac if the fuse blows your stat is bad if it doesn't then check your wiring going to the condensing unit. disconnect the control wires at the contactor and cycle the ac if fuse blows bad wiring if not ohm out the contactor or replace it.

 

[MFolks]

Rats or mice chewed wiring,also?

 

[OccupantRJ]

Have you used a weed trimmer near the outside unit recently?

 

[bonneyman]

You've got a short somewhere, either in a wire or a component.

Go to the condensing unit, open the side panel (disconnect off), and pull one of the wires on the contactor off. Replace the fuse in the furnace, turn the AC on again. If it blows, that's a short in the wiring. If it doesn't blow, ohm out the coil on the contactor. If it's less the say 5 ohms, it's bad. Replace it. The newer Chines made components **** at QC.

If the short's in the wiring it'll be a bit more involved to find

 

[Reit38]

Thanks for all the replies guys. I am camping this weekend. Hope to try all this Sunday night when I get home. Wires from stat to furnace is one solid run of new wire. I looked before we left Friday and it looks like theres electric wire on the 2 wires outside going to the AC I'm gonna check out

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