Day & Night Carrier Package unit - Blower fan runs Continuously


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Old 09-11-13, 01:42 PM
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Day & Night Carrier Package unit - Blower fan runs Continuously

I have a Carrier model: package unit, 3.5 ton
model: 584AN042060AC
serial: 4991C20062 (yr 1991)

This is another one of those blower fan runs continuously, but with a twist.
We had hot weather the last week and the A/C has been running pretty heavily, but operating normal with the blower fan cycling off as you would expect. Now that the weather has cooled off at night, the blower comes on by itself early in the morning at say between 2:00 am - 4:00 am!
I am able to reset the system back to normal (by cycling cb and cycling cooling thermostat down and then back up).
This is an intermittant problem, but seems to occur almost every morning while we sleep.
Things I have tried are: replaced roll-out limit switch, checked transformer voltage (27v). I am good with a multimeter, is there another limit switch or other to check?
thanks, Greg R.
 
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Old 09-11-13, 04:24 PM
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Is it possible that you have a programmable thermostat that allows you to set up different operational programs based on your needs and it somehow got set to come on between 2:00 and 4:00 a.m. fan only?
 
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Old 09-11-13, 04:28 PM
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No, I don't think so. I have the programmable thermostat on "Hold" mode, so it should ignore all programs.
 
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Old 09-11-13, 04:54 PM
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That is an unusual problem since it only comes on by itself between 2:00 and 4:00 a.m. I have never run across that particular problem before! Even though you have the thermostat on "hold" mode I would go ahead and review the program setup(s) to verify there are no other programs that inadvertently were set to activate. Is the thermostat powered by the common wire from the transformer or is it battery activated? I have seen some strange things occur when the batteries on a battery only operated thermostat get low on charge. Have you noticed any water dripping on the control board?
 

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Old 09-12-13, 08:32 AM
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i studied the thermostat again and there is no fan-only mode, just the usual start, leave , return, etc. Also, indicates on HOLD mode. Battieries good.
The fan woke me up at approx 3:05 am this morning! I went on the roof and made the voltage readings across both limit switches. There is no open in the limit loop. All voltages 27v to ground.
I did notice it was damp on top of the unit and the roof a bit slippery from dew.
the cb is off right now.
I am starting to suspect a bad relay on control board...
 
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Old 09-12-13, 09:01 AM
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I am starting to suspect a bad relay on control board...
It very well could be the control board. Another possibility could be a low voltage wiring issue. Intermittent and "phantom" problems are the most difficult and frustrating issues to identify and correct. Was there any obvious moisture on the control board itself? The only other thing I can think of is that there is a condition that causes the fan control wire (connected to "G" in the air handler) to touch somewhere that causes the fan start to up. Possibly there is a spot on the wire where the insulation is missing and rubbing to turn it back off. Thinking of all possibilities, perhaps a breeze or quick gust of wind blows the wire just right to make contact and start the fan and then another breeze/gust comes along and moves it just enough to break the contact. I would inspect all of the wires on the control board and all of the wires where they are connected to the incoming thermostat cable wiring to ensure all of them are properly connected and are well separated so they will not touch each other.
 
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Old 09-12-13, 09:47 AM
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OK, in about 7 hrs I will be home to do as you suggest above. I want to eliminate the t-stat as the problem, so I will try removing the G wire at the control board. Also I will take photos of that control board area.
 
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Old 09-13-13, 11:38 AM
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getting closer

OK, here's an update:
I wanted to eliminate the t-stat as the problem, so I removed the G wire at the control board.
I Re-energized unit, and went to bed. At 5:30 am today (yes it cooled down to about 67 degrees) and the fan came on again, yikes!
I believe this eliminates the t-stat and associated wiring as the problem.
I never did find any moisture in the unit, never found any problem in the limit switches or wiring of the red and purple wires loop.
Also it was fairly clean!
This is a very intermittant problem, but I can rely on it happening once per day!
It seems to reset itself (fan off) if I open and reclose cb during the afternoon, however does NOT reset easily during early morning hours (fan keeps running).


The control board is: HH84AA017
Looks like I can easily find this on ebay or other part sites for about $110. See photos, do I need the control board or the piggy back smaller board?
For those who use JohnstoneSupply.com , it looks like they do not carry a replacement board??
Is there anything else I can check before I purchase the control board?
thanks in advance. Greg R



 
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Old 09-13-13, 01:21 PM
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do I need the control board or the piggy back smaller board?
That is hard to say since your problem is intermittent. The "piggy-backed" board appears to be a time delay board. Not sure how this operates on your unit but normally the purpose of the time delay relay is to start the blower a few seconds (something like 5-15) after the compressor starts and then continues to operate the blower depending on the selected setting up to maybe 90 seconds. I couldn't find a schematic for your unit. Hopefully one of the regulars here that is familiar with your system will come along and give you some good advice. If it was me, first I would remove the time delay relay and see if that corrects the issue you are having. If that didn't correct it, then I would look at the control board.
 
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Old 09-13-13, 01:27 PM
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schematic

I have the schematic.
I believe now, the piggy back pc2 board is for the small inducer motor IM, fan.

what do you guys think?
 
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Old 09-13-13, 02:01 PM
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Yes, the time delay and the inducer motor relay are actually the same part number. It looks like the p/n is HH84AA018. Some manufacturers call it by other part numbers and is listed by some as an inducer motor relay, others as a time delay relay. What I would suggest at this point is to look for corroded terminals on all of the connections. Turn the power off to the unit and verify it is off with your meter. Then systematically one by one pull each wire off the terminals and inspect it for corrosion. Being in a damp environment, the terminals/wires tend to build up corrosion and can cause intermittent problems. If that doesn't solve the problem I would say it is the control board. Also inspect the control board for any signs of burned looking/discolored areas. Sometimes parts will become "un-soldered" and cause problems. Some people choose to try and repair those areas if they have the knowledge/skills. I am a believer that it is a good sound practice to replace those types of components.
 

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Old 09-16-13, 09:39 AM
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I went ahead and ordered the fan control board HH84AA017
Friday night from Extreme Air Service (Miami). Of course, since then it got hot again and the AC is running every day, also, the symptom went away for now.

As I am replaceing the control board, I will check every 1/4" blade connection for corrosion.
 
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Old 09-16-13, 09:53 AM
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I was hoping you were going to check the control board for corrosion to see if that was the source of the issue before ordering a new board. But, hopefully it will solve your problem. Please let us know how it turns out.
 
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Old 09-16-13, 09:55 AM
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I was feeling the pressure from the wifey, so thought I'd speed things up a bit. I am really appreciating your help and will reply back after new board is in.
 
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Old 09-16-13, 10:03 AM
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I was feeling the pressure from the wifey
Understandable. Mama happy, everybody happy!
 
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Old 09-30-13, 11:22 AM
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Mission Complete

I am finally reporting back on this!
It took about 10 days for UPS to ship the new blower control board to me (Miami to Los Angeles ground).
Saturday morning I labelled all the existing wires and removed them. Then reinstalled the new control board and then mounted the PS2 daughter board on top also. All wires reattached to both boards.
Thank God the US Navy gave me excellent training as an electrician's mate (note: I was not an Aviation Electrician's Mate like the Navy Yard incident bad-guy).
Closed in the breaker and tested in A/C mode first, then tested the Heat mode this morning. Everything works perfectly!
thanks for all the help!
Greg
 
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Old 09-30-13, 11:30 AM
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Glad to hear you got it back up and runnin'. It feels great to accomplish something like that DIY. Thanks for updating us on the outcome.
 
 

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