Carrier central A/C Diagnostics


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Old 05-27-10, 12:07 PM
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Carrier central A/C Diagnostics

Hello,

I have High Efficiency Carrier A/C unit which is not functioning. Can anyone point me to a diagnostic/service guide or advise on how best to diagnose the problem. Here are the details:

1. Carrier 3PTA024300, Approximately 8 years old
2. Controlled by new Bryant Evolution control which also controls a new Bryant Furnace.
3. The large blower fan on the Carrier A/C is shutting on and off repeatedly. Its on for a few secs and then shuts off for a few secs. The process repeats.
4. Measurement of the control signal to the Carrier A/C (from the Bryant Evolution looks to be a steady DC signal.
5. All the wire inside look ok. No loose connections
6. Maybe a safety is being tripped?

Can anyone help? Thanks.
 
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Old 05-27-10, 07:26 PM
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Push and hold "Advanced" for 10 seconds or untill the screen changes.

Scroll down to "Checkout" using the silver scroll bar.

Select "Last 10 System Faults".

What does it display?
 
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Old 05-27-10, 09:05 PM
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Hi Houston204,

Thanks for your reply. I've provided detailed information below for you plus other information that might be helpful. The original installer told me about the advanced computer control and diagnostic system in the unit but I forgot all about it. Wow. Pretty neat.

1. "Last 10 System Faults"
- This was in the diagnostic menu and under the "Service" selection (and not the "Checkout" selection)
- There was one entry but it was from March as follows:

"FN 3/8/2010 10:36PM F
41 - Blower Motor
Fault
1 - Event

F=Failure"

- This seams to indicate another (unrelated) problem back in March with the Furnace motor?


2. "AC Cycle Counter"
- This was in the diagnostic menu under the "Checkout" selection and then "Run/Fault History" and then "AC Cycle Counter."
- Screen reads the following:

" AC Cycles
Power 14
Cool Stage 9

3. "AC Lifetime hours"
- This was in the diagnostic menu under the "Checkout" selection and then "Run/Fault History" and then "AC Run time"

" AC Lifetime hours
Power 2828
Control Stage 2"


4 "AC Check"
- This was in the diagnostic menu under the "Checkout" selection and then "AC Check"
- It was set to run for 5mins but I ran it for less than 60sec
- The screen read as follows

"AC: Cool
Airflow CFM: 700
Outdoor Temp: 21
Blower RPM: 640
Static Press: 0.35"

- During the time that the AC Check was being run, I ran outside to see what was happening with the Carrier AC unit. It was doing exactly as earlier describe: The fan would spin up and the relay would click off (I can hear it) and then it would spin up again. The process would repeat itself.
- I'm assuming that the above measurements are from within the furnace and blower in my basement and not with the Carrier AC unit?


Does the above provide any clues? I can do more checks if it will help.

Thanks in advance.
 
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Old 05-27-10, 09:08 PM
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Hi Houston204,


I forgot to clarify in my original posting. The new Bryant Evolution Control and Bryant HE furnace was installed in January 2010 during the winter. The HE Carrier A/C unit appears to be about 8 years old. The A/C was working last year and this is the first time we've tried it with the new Bryant system.


Thanks again.
 
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Old 05-29-10, 10:29 AM
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For some reason, I cannot login to Carriers site today. I'm not familiar with your Carrier model number. (Usually starts with 38 and I'd have guessed 38TDB)
Does the stat display your outdoor unit model number in "advanced options" "model and serial numbers"?

Does the outdoor unit have a blinking LED with a reference chart on the control panel?

I was checking a Carrier Infinity control yesterday and saw that Last 10 system faults is in Service as you have posted
 
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Old 05-29-10, 11:29 AM
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I get nothing at Carrier with that model either. Recheck.

As far as age. Look at the serial number. If it's like 1088G, this would have been built in the 10th week of 1988.
 
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Old 05-29-10, 07:06 PM
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Hi everyone,

Thanks again for your efforts. You guys are definitely on the ball. I've made a typo in my original posting and missed an "8". It should have read as follows:

1. Carrier 38PTA024300, Approximately 8 years old

Thanks again
 
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Old 05-30-10, 08:04 AM
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That works. Nothing fancy there. I suspect the fan is shutting off on internal over load. Could be the capacitor or the motor itself. Look at the cap, is it buldged out, leaking? Cap is 20 bucks, motor is $100 if DIY.

38TPA is an 11 SEER unit. Production from 2001 - 2003, thereabouts.
 
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Old 05-30-10, 09:12 AM
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Hi Jarredsdad,

Thank you for your experienced insight. I've briefly took off the side panel on the unit to have a look just before posting my original posting. There's a printed wiring diagram just on the inside. Before I progress further to check the possible cap/motor that you mentioned, is there a service manual/disassembly manual for the unit that one can get? I tried to look for one on Carrier's website but couldn't find one.

I'm mechanically/technically inclinded as well as having a general idea of how an AC system works (I've even fixed my own fridge before) but this would be my first HVAC unit. I know at least to shut off the 240V going to it before dismantling but a service manual would be useful.

Thanks.



Jean
 
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Old 05-30-10, 10:26 AM
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http://www.docs.hvacpartners.com/idc...it/38-11sm.pdf

Page 14 figure 14 is your capacitor.

Capacitors can hold a charge for a few minutes after removiing power


This condenser would not recieve DC voltage for a control signal.
 
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Old 05-30-10, 09:44 PM
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Hi Houston204,

Thanks and thanks also for the warning. I'll ensure that I discharge it before touching it...else you'll know why I don't respond back.

I'll reply back either way on progress to help close to loop to help others in my situation on this forum.

Thanks.
 
 

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