AC issues

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Old 07-04-14, 11:08 AM
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AC issues

Hello,

I have a 2006 Carrier AC/Furnace. Model # on outside unit is 24ABR330A310.

The AC has not worked this season. It would not turn on when it got hot and we attempted to use it. Using the thermostat, I can get the fan and furnace (heat) to run. I have changed the filter and confirmed that the condensate pump works.

After reviewing this troubleshooting article:

DIY Air Conditioner Repair: The Family Handyman

I confirmed power (240) at the outside box, confirmed that the fuses in the box are good, replaced the capacitor (3 pronged type) and the contactor. The AC is still not working.

Not sure what to try next before calling a repair man. Not sure how to test if the fan motor is the problem, but when the thermostat is set to cool I also do not hear anything (fan does not spin and compressor does not hum) at the outside unit.

Consider myself a novice, but avid DIYer. Any suggestions are much appreciated. Thanks.
 
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Old 07-04-14, 11:21 AM
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That's a poor article. The only electrical testing they did was for the fuses. You have 240 at the outside box, thats good. So is the contactor being activated when it calls for cool? If not, you need to see if you are getting low voltage power to it. It will be 24vac on the smaller wires attached to the contactor.
 

Last edited by PJmax; 07-04-14 at 11:34 AM. Reason: what's a few volts amoung friends.
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Old 07-04-14, 11:27 AM
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U don't do troubleshooting by replacing components; you test & confirm what is causing the problem!

With 240-volt power OFF at the breaker box or the disconnect...
You need a low cost multitester to test if there is 24 volts to the contactor coil.
If the fan will run the Transformer is okay so there would be a problem with getting voltage to the contactor coil.
 
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Old 07-04-14, 11:29 AM
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I think gunguy meant 24 VAC.
 
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Old 07-04-14, 11:32 AM
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Oops...I always make that mistake because I think solenoid=DC (like all the ones in cars).
 
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Old 07-04-14, 11:34 AM
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Thanks. I now realize that maybe it was not the best article. The article did suggest replacing the parts to rule out some of the simpler fixes, but I know that this can lead to replacing multiple parts (including good ones).

I did use the multimeter and checked the ground coming in and each of the wires attached to the contactor. Each time I did this I had 120 volts.
 
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Old 07-04-14, 11:39 AM
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Those are the big 240V leads. Did you just check the input or the output as well when calling for cool?

The low voltage is the small wires...normally on the sides of the contactor. If you swapped contactors, you'll know the ones I mean.

Simple check is turn stat to off. Wait 5 min and while watching/listening the contactor, have someone turn the stat to cool. It should click and the contacts should pull in.
 
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Old 07-04-14, 11:44 AM
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If you got 120V on all four terminals that means the contactor is pulled in. Take a look at the capacitor and see if the top looks bulged out.
 
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Old 07-04-14, 12:03 PM
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skaggsje - I replaced the capacitor. The old one was not bulged out or leaking, but I read that sometimes they do not do so.

Gunguy45 - I will check the side wires; I know which ones you mean.
Also, the neutral (white) wire coming into the unit (that attaches to the bottom of the contactor) originally looked charred (black and green/corroded). The screw that held this wire was the only screw that was rusted on the old contactor. Does this mean anything? When these contactors go bad can they "fry" the compressor? I did clean up the wire, and confirm 240 going into the contactor.

Also, what does it mean if the new contactor does not click, like you suggested?

Thanks again for the help. I really appreciate it.
 
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Old 07-04-14, 12:10 PM
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If it doesn't click or pull in, it means you aren't getting the low voltage somehow or the new contactor is bad (unlikely).

Btw...on a straight 240V circuit, there isn't a neutral. If the wire was blackened, it could have been from a bad connection producing more heat. Likely that's what it was since the same amount of current is flowing through both hot leads.
 
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Old 07-04-14, 12:19 PM
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Got it. Thanks! Can that extra heat fry something other than the contactor, like the compressor?

Also, the unit had been on at the thermostat, but not running as we had tried to turn the AC on a week ago. When I discharged the capacitor nothing happened (no spark, etc.).

I realize like HVAC RETIRED posted that parts should not just be replaced. However, the article made it sound that those parts often fail, that they should be replaced to rule them out as the problem, and they were relatively inexpensive.

Thanks again. I will check the lower voltage and complete your "click test".
 
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Old 07-04-14, 12:24 PM
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Also, if the button on the contactor does not pull in with the AC set to cool - is it okay to push it in to see if the unit will then run? Is this an okay way to check to see if the issue is actually at the thermostat?
 
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Old 07-04-14, 12:30 PM
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For a short time, yes. Use an insulated screwdriver or similar. The issue may not be the stat. More often it's a broken wire somewhere or bad transformer. As HVAC said, since the blower is working in heat, it's likely not the transformer (which is located with the furnace/airhandler).

As to the bad connection....well, I don't really know but I doubt it. If it were really poor I guess it could cause the compressor to pull more amps but I'm not sure. Probably see other issues first.
 
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Old 07-04-14, 12:50 PM
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If you got 120V on all four terminals that means the contactor is pulled in. Take a look at the capacitor and see if the top looks bulged out.
That is not correct. If that is a single pole contactor all four terminals will show 120vac to ground

You need to see 240vac on the line (L1+L2) terminals and then 240vac on the T1+T2 terminals. Seeing 120vac tells you nothing.
 
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Old 07-04-14, 12:57 PM
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You need to check the thermostat wiring where it enters the compressor unit. You may have to remove an access panel to see the wire nutted connections. You need to verify 24vac to those two wirenutted connections. If you have 24vac there and not at the contactor then most likely your are low on refrigerant and the low pressure switch is open.
 
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Old 07-04-14, 01:12 PM
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Are you saying that a 1 pole contactor (denergized) will show 120 to ground on all four terminals?
 
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Old 07-04-14, 01:21 PM
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Yep I get that....it flows across the non switched side, though the compressor windings.
 
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Old 07-04-14, 01:44 PM
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Thanks gunguy I rarely run across 1 pole contractors.
 
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Old 07-04-14, 01:57 PM
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I pole contactors are actually more common than the two pole type.
I doubt it would have any thing to do with cost.
 
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Old 07-04-14, 05:14 PM
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Thanks pj ,even at my age I'm still learning.
 
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Old 07-05-14, 01:26 PM
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Update:

Tested the wires on the sides of the contactor for 24 VAC. Less than 0.01 VAC is present there.

240 at the bottom of the contactor. 240 on the left side (top to bottom). Minimal voltage (0.03) across the top and on the right side (top to bottom).

Pushed in the button on the contactor; AC unit started up.

Checked the wires coming in that connect to the wires that are on the side of the contactor. One is red and one is white (and I believe someone said these are the thermostat wires coming into the outside unit). They seem fine (not broken). Someone mentioned checking for 24 VAC there; do I have to remove the wires nuts to do so? Should there be 24 VAC between these two connections with the wires nuts on them?

Troubleshooting thus far leads me to believe that something (thermostat?) is not telling the AC unit/contactor to turn on - as I was able to manual turn on the unit by depressing the contactor button.

Can the thermostat be bad even if it will turn on the inside fan and furnace, but not the outside AC unit? If so, does the thermostat "face" get replaced (the part that comes off the wall and has the "board" in it)?

Thanks a lot.
 
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Old 07-05-14, 01:58 PM
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There are pressure switches and delay relays in line between the wires coming from the house and the contactor, so just checking at the contactor isn't reliable to check for available control voltage. You need to disconnect from the wire nuts, then have the stat call for cool, now you should read 24VAC. If not, it's a problem inside the house.
 
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Old 07-05-14, 04:38 PM
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Thanks.

I should disconnect the wire nuts (to stop any "input" from the house) and should check for 24 VAC when testing both wires that come out from the left and right sides of the contactor. Correct?
 
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Old 07-05-14, 06:22 PM
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NO...... the house wiring can stay connected to the A/C unit. Either push the probes inside the wirenuts or remove the wirenuts but leave the wires connected.
 
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Old 07-05-14, 06:31 PM
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The problem is if the wirenuts are put on hard, you may not be able to get a good reading.

The "input from the house" is what you are looking for.
 
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Old 07-06-14, 09:26 AM
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Thanks.

I tested the two sets of wires on the left in this picture. I have a fraction of 1 VAC with the thermostat set to cool in the house. Does this mean there is an issue between this point and the input from the house? Could the issue be the thermostat itself? Or, one of the relays/switches that you mentioned earlier?

Thanks again.
 
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Old 07-06-14, 09:38 AM
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AFAIK, the relays and pressure switches are after that point in the outside unit. Now that we have a good pic, the Pro's will be able to help better I think. They know the color codes and where you should check next better than I.

I don't like the look of that blackened wire.
 
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Old 07-06-14, 12:03 PM
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Ok. Thanks.

That bottom white wire actually looked worse; the exposed part had to be sanded to return to the copper you see. As I mentioned in an earlier post:

"Also, the neutral (white) wire coming into the unit (that attaches to the bottom of the contactor) originally looked charred (black and green/corroded). The screw that held this wire was the only screw that was rusted on the old contactor." Note - I now know that this is not a neutral wire.

The condition of this wire (albeit wrongly) led me to believe the contactor may have been bad. Now, I understand I should have done further testing before assuming such. In fact, just to see I put the old contactor back in. Pushing in the button on the contactor did the same thing - the unit activated (fan and compressor).

Gunguy45 - I really appreciate the assistance and help!

I can also post more pics if this will be helpful.
 
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