# Carrier Infinity Thermostat lost power - won't power up



## Plumber101

Remove the thermostat from its base.

Using a volt meter measure voltage between Terminal R and C.

Should have 24 vac


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## how

Are you saying the thermostat lost power so nothing is reading on the thermostat or are you saying you are not getting any heat?

Does your thermostat have low or dead batterys? Replace them if so.

If the batterys are good and you don't have an electrical meter, you can remove the thermostat sub base and jumper the R & W for temporary heat and to check if those thermostat wires & connections are good.
Let us know what happens


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## The Raddish

I'm saying the thermostat is completely turned off. No display, no LEDS, nothing on the screen. I'll check for voltage in a bit and report back.

I don't need heat, but tomorrow is going to be 85 and humid. So I have time.


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## Plumber101

If you don't have 24 vac across R and C then jump R to G to see if the fan come on.

If the fan comes on then you have 24vac to the stat and lost the connection between the stat and furnace on the wire connecting the C

If the fan doesn't come on then check voltage at the furnace between R and C if you have 24 vac then you lost the connection between the furnace and stat on the R connection

IF you don't get 24 vac at the furnace double check the fuse. If the fuse is ok you may have a transformer out or control board


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## The Raddish

Okay, I got the thermostat off. I have four wires:

A - green
B - yellow
C - white
D - red

My volt meter is at work (the one time I forget to bring it home).


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## Plumber101

Jumper Red and Green should turn on fan


Makes no sence though. Only four wires should have 5 for a ground

Red - 24 vac
green - fan
yellow - a/c
white - heat


Sure your stat doesn't need new batteries?


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## hvac benny

C (common) and D (hot)are where you want to check for 24 volts. Doubly check that the wires are inserted correctly into the t-stat as well as the green connector on the other end.


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## hvac benny

Plumber101 said:


> Jumper Red and Green should turn on fan
> 
> 
> Makes no sence though. Only four wires should have 5 for a ground
> 
> Red - 24 vac
> green - fan
> yellow - a/c
> white - heat
> 
> 
> Sure your stat doesn't need new batteries?


The Infinity stat is Carrier's communicating stat: A and B are data, C is common and D is hot. It could be that the stat or it's screen have died, I've had a few of those.


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## The Raddish

Jumping red to any of the others does not produce any action.

Back in the attic, if I remove the fuse then no LEDS light when power is applied and the interlock held down. If I insert the fuse, I get a green LED for about a half second, then instead I get the amber LED. This tells me the fuse is not the problem.

The wires in the thermostat are tight in the jumper block.


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## The Raddish

hvac benny said:


> The Infinity stat is Carrier's communicating stat: A and B are data, C is common and D is hot. It could be that the stat or it's screen have died, I've had a few of those.


It's not just the screen. None of the LEDs are lit either, and the HVAC unit doesn't run at all.


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## hvac benny

The Raddish said:


> Jumping red to any of the others does not produce any action.
> 
> Back in the attic, if I remove the fuse then no LEDS light when power is applied and the interlock held down. If I insert the fuse, I get a green LED for about a half second, then instead I get the amber LED. This tells me the fuse is not the problem.
> 
> The wires in the thermostat are tight in the jumper block.


DO NOT jump the wires in that stat, it does not work the same way that a conventional stat does. You need to measure if you are getting 24 volts between C and D. Is it a furnace or fan coil that you have? You can try jumping R and W in the furnace, disconnecting the green bus connection.


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## The Raddish

It's a 16.8 SEER split system, that acts like a heat pump when only mild heating is needed, and uses gas when it gets cold. The compressor is a multi-stage compressor. It is four years old next month.


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## kilosos2

That really sounds like either your control board is bad. Or for sure your thermostat is out. If you have the led light on even though its amber color then you have some sort of 24 vac coming into the control board. Although it still could be the transformer isn't producing enough 24 volts to power up the control board, that is possible also. Amber led may indicate just that the unit is off. Kinda like in your computer when it goes into sleep mode. Let us know what you find. Try what hvac benny is saying to do.


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## The Raddish

Turns out the limit switch turned off the system because the top drain pan wasn't draining. Cleaned out the drains and vacuumed out the drain pan. System turned on, working just fine.


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## The Raddish

Well hell, now the air coming out of the unit is mildly cool, not cold as it has been. Did the system lose its mind and do I need to go back into the advanced settings to turn on the 'cold' air somehow?

The day this thing quit working, it was spitting out very cold air. Now the air is only slightly cooler than ambient.


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## The Raddish

Alright, now I'm pissed.

So it turns out there is a leak in my coil in the attic. The company who sold me the unit wants $680 for labor to replace it, though the coil itself is still under warranty. I have to dig up the paperwork, but the smarmy sales guy who sold it to me said that it had a 10-year "bumper to bumper" warranty, including parts and labor.

The unit is only four years old.

Is $680 in labor unreasonable? They originally quoted me $1500 for labor but I pitched a royal fit. I paid nearly $10k for the system in 2008.


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## beenthere

680 sounds cheap.


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## Mamou

*Same issue with dead stat.*

I have the same problem with the dead thermostat. Happened 2 nights ago around 8 PM. Started troubleshooting and found no comm leds on any of the boards (outside, inside unit and baffle control boards). insdie unit board has amber led but no green comm. Checked and found 24vac getting to the board but not out to stat or outside board. Played around and started clicking the service disconnect switch on the inside unit and finally the comm led lite and everything worked fine for about 24 hours. Last night around 8 PM same thing. Did the same thing opened the inside unit up and after playing around for about 15 mins and clicking the cutoff swithc many times comm lit and woking fine. Also yes I checked the float cutoff and see not problems with them.

I did notice I have 24 vac on the D when it is not working if I ground my meter to the chassis but not to C. In other words when unit is goor I have 24 vac across C and D. when it is not I have 24 vac between chassis and D but not between C and D. All fuses are good or check good with a meter! any ideas? I am assuming the 8PM is just a coincidence? Any other checks I can make?

I did find this on this on the net. If or when it returns I will check some of that?? http://gpsinformation.info/joe/carrier/Infinity-Evolution Communication Faults-Troubleshooting.pdf

Any other suggestions? I guess the internal board could be bad??


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## Mamou

Also to original poster, concerning bad coil.

I had a bad coil as well. Original quote was for warranty coil changout about $750. I told them to order it but called around to 3 other dealers the next morning. All other quotes was for $400 to $480 max. Called my delaer back and raised a little and he did it for $500. I had one guy tell me Carrier had bought coils from India for a couple years and that was the junk coils that were failing. I wrote Carrier and they reimbursed me for the $500 it cost to replace the coil. I was impressed with Carrier for doing the right thing. My unit was installed around 2006 and coil went out around 2009 to 10 frame.


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## jagans

Thanks Mamou. To me its not the screw up, its the recovery. Carrier sounds like a decent company that stands behind their products.


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## Mamou

I guess their mistake was going with cheap copper from India (that I think they corrected). But the bright side is they made good on it for me at least.:thumbsup: I will buy Carrier again!:yes:

On the other note. I think I found the problem. Tonight at 6 PM the stat went dead. Started checking voltages and found I was not getting voltage through the 2 float switches on my unit. I have one in the pan(it was dry) and one in the discharge pipe. I pulled the little cap off and a little water spilled. It was full and plugged somewhere. I think before I was not noticing the unit was down until the water had a little while to drain then it would work again. Crossing my fingers but I think this was the problem.:thumbup:

Thanks to DIY for having this forum for us DIY guys. And thanks to the experts that come around to help!!


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## parki3n

I had this same issue with my Carrier Infinity system, which suddenly shut of one day. My situation turned out to be exactly the same as The Raddish's initially was, so thanks for posting about it. The emergency drain pan underneath the unit was full and had shut off the system. After removing the side panel and looking inside, the internal drain pan was full too and had clogged. Someone left the installation instruction sheet in there when the unit was put in and it had slowly collected enough dirt to stop the water from flowing at all.

I've never worked on an A/C system before, but this was really easy to open, clean, and get working again on my own.


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## sktn77a

The Raddish said:


> ........but the smarmy sales guy who sold it to me said that it had a 10-year "bumper to bumper" warranty, including parts and labor.
> 
> The unit is only four years old.


If you have a 10 year labor warranty (which most of the high-end Cariier Infinity dealers offer) then you shouldn't pay a penny. Do you have the original estimate/invoice/receipt with this stated on it? 

Failing that, $680-up to change out a coil is pretty typical (and $10,000 is fairly typical for the top of the line Infinity setup).


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## mattdon1

Replying to an older post, but I just want to say thank you! I followed the directions to change the fuse and I'm back up and running (for now anyway).


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