No display on thermostat but air is blowing

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  #1  
Old 11-07-12, 12:36 PM
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No display on thermostat but air is blowing

I have a York unit outside and it is blowing but it doesn't feel like warm air and the thermostat is blank. It is a Honeywell T8400C (no batteries needed) and sliding the controls to Cool/Off/Heat changes nothing, air still blows. I pulled it off the wall and air still blows. I turned off the breaker marked "Heat" in my breaker box (it was not tripped) and back on, no change. Turned the breaker off outside that goes to the York and it stopped blowing but when I flipped the breaker on it immediately started blowing again.

I have a multimeter and tried to test the power to the thermostat. From what I read it should have 24v power coming from the transformer, right? Not sure how to use this multimeter but I set the dial to 20 Vdc and bridged the red and green wires and got a reading of 0.19--I have no idea what that means. Even with the thermostat removed from the wall, the blower is on.

Other than calling someone, I don't know what to do. I just bought a new HVAC for the upstairs last week, I'm out $5k and now this...really really bad timing. Any advice is much appreciated.
 
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  #2  
Old 11-07-12, 12:38 PM
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Take the cover off the burner compartment of the furnace. Obtain the make and model of the furnace off the rating plate in the burner compartment and post it here.

Observe the sequence of events that occurs at the furnace when you turn up the thermostat and post that sequence of events in order and in detail.
 
  #3  
Old 11-07-12, 12:40 PM
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Forgot to mention, if it matters...the thermostat was set to Cool and was working yesterday. This morning my wife switched it to Heat and I'm not sure if it ever actually switched to heat, but it was some time after that when I noticed the display was blank.

Take the cover off the burner compartment of the furnace. Obtain the make and model of the furnace off the rating plate in the burner compartment and post it here.

Observe the sequence of events that occurs at the furnace when you turn up the thermostat and post that sequence of events in order and in detail.

I'll try to find wherever the cover is supposed to come off, although I am so out of my element at this sort of thing. However, I can't turn up the thermostat--it is digital and there is no display and the system is not responding to the switches at all.
 
  #4  
Old 11-07-12, 01:56 PM
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If there is a door on the unit, I can't tell where it is, but the model is York D1NA024N03606C. As I said, I can't make the thermostat do anything, but I turned off the breaker for the York for fifteen minutes then turned it back on. When I did that, I heard a hum followed immediately by a click, then five seconds later the blower came on. The air blowing through the vents is cold, but it is about 45 degrees today so I don't know if the unit is on Cold or if it is on Heat but just not heating or if it is just broke and blowing outside air around the house.
 
  #5  
Old 11-07-12, 01:58 PM
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The manual on your thermostat can be found at:

https://customer.honeywell.com/resou...0s/69-1480.pdf



Set your multimeter to the next voltage setting above 20 VAC.

Locate the electrical connection strip on your furnace that the thermostat wires connect.

Coonect one lead from your multimeter to the C terminal or to the furnace sheet metal (ground). Measure the voltage to the R terminal and the W terminal and report that here.


The R terminal is the point of origin for voltage to turn the furnace burners on using the thermostat. When the thermostat switches voltage on to the W terminal, the furnace should start.

You can jumper the R and W terminals with a piece of wire which should cause the furnace to switch on.
 
  #6  
Old 11-07-12, 02:27 PM
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I already looked through the manual for the thermostat, but I don't understand how that is relevant if I'm supposed to be working outside on the furnace...is that what you mean? Or do you mean take the thermostat off the wall and test the wires there?

I'm sorry but you may have to talk down to me.
 
  #7  
Old 11-07-12, 02:45 PM
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With the thermostat removed, I have a wiring panel. Measuring there with the multimeter on 200 Vdc (the next setting above 20), G to R is 00.1 and G to W is 00.0. Bridging R and W did not seem to have any effect--the air coming out of the register is still cold.

Why is it still blowing even with the thermostat removed?
 
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Old 11-07-12, 03:13 PM
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Locate the electrical connection strip on your furnace that the thermostat wires connect.


Work on the furnace, not the thermostat.
 
  #9  
Old 11-07-12, 03:18 PM
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I probably don't have the ability to do that...I don't even know how to open the thing. It is one of these big "package units" and I guess it's time to call someone I suppose.

I keep asking this but is it not unusual for it to be blowing air without the thermostat connected? No guesses as to what I'm looking at? I am pretty sure he will just tell me I need to buy a new unit, that it's not worth fixing a unit that is 10 years old...that's why I just bought a new unit for the upstairs.
 
  #10  
Old 11-07-12, 03:36 PM
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Is it safe for me to leave the unit blowing or should I turn it off at the breaker?
 
  #11  
Old 11-07-12, 03:44 PM
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<< I keep asking this but is it not unusual for it to be blowing air without the thermostat connected? No guesses as to what I'm looking at? I am pretty sure he will just tell me I need to buy a new unit, that it's not worth fixing a unit that is 10 years old...that's why I just bought a new unit for the upstairs.

Read more: http://www.doityourself.com/forum/ga...#ixzz2BaEEopKN
>>


My guess is you have a defective thermostat or bad wiring to the thermostat. But if you don't have the confidence to identify what's going on with the furnace, I can't help you.


If you can't trust your repairman to deal with you honestly, get a different repairman. There are all too many outfits where repairman get paid for telling people they need to buy new equipment rather than repair what they have.
 
  #12  
Old 11-07-12, 04:08 PM
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I wouldn't say it's a lack of confidence as much as a lack of knowing how to do it. I don't see a door, I can't find a manual for the unit. I see some pry marks on the top of this package unit which make me thing maybe I'm supposed to take the whole top off, but I just don't know how to proceed. Without that information, I don't want to do something stupid like making matters worse.

Should I leave the unit blowing or should I turn it off at the breaker?

It still amazes me that the unit is blowing without a thermostat connected. I thought the thermostat is where those connections were made, so without those connections, it seems like it shouldn't be doing anything.
 
  #13  
Old 11-07-12, 04:20 PM
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Just talked to a neighbor who says I've been asking the right question, just not getting an answer here. Says removing the thermostat should turn the package unit blower off, so it isn't simply a bad thermostat. Just mentioning it here in case anyone else in the future finds this thread.
 
  #14  
Old 11-07-12, 06:01 PM
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You can ask all the questions you like, but unless you start providing answers to questions already posed, it's not likely to do you much good.

Perhaps your neighbor can find the door to the burner compartment of the furnace for you.
 
  #15  
Old 11-07-12, 06:31 PM
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Perhaps he can.

No disrespect intended, but I've repeatedly asked questions you have refused to answer. Perhaps they are beneath you, but I know nothing about this stuff. I've provided all the information I can under the circumstances, and I can't figure out how to get inside the package unit, but I'll keep trying. In the meantime, could you please answer for me, if you know:

- Is it normal for the blower to come on with all wires disconnected from the thermostat?

- Should I leave the unit on and running? Could I be doing damage by leaving it running or should I shut it off (flipping the 25A breaker outside is the only way I can do that)?

And here is a new one:

- You keep calling it a furnace. Why is that? This is a package unit, and it's not putting out heat or cold, although it is blowing. Am I specifically looking for the furnace component of this unit?

I'll take another crack at opening the unit tomorrow, but if you could please answer my questions, even if they aren't relevant to you, they might help me keep things straight in my own mind. I am starting at zero, trying to come up to speed. Your patience is appreciated.
 
  #16  
Old 11-07-12, 08:38 PM
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Some pieces of equipment are designed to turn on the fan when a defect occurs. Others can switch on the fan in various ways.

The short answer is, without knowing more about the furnace I can't give you an answer.

Having the fan run all the time probably creates annoying drafts. You can turn off the power and shut off the fan that way if you wish. It will do no harm.

I call it a furnace because it's convenient, and because you are interested in using the furnace portion of the system. If you want to substitute "package unit" for "furnace," help yourself. Either term is fine.

You may see where the thermostat wires enter the furnace. That's what you want to uncover. Once the sheet metal cover is removed you will see a series of electrical connections to which the thermostat wires connect.

It may be that this isn't a task you are able or willing to perform. That's certainly fine ---- the first question any do it yourselfer needs to ask is "Is this a task I am interested in doing?" The answer for you may be "no." I have DIY tasks I don't do too.
 
  #17  
Old 11-11-12, 12:14 PM
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Set your multimeter to the next voltage setting above 20 VAC.

Locate the electrical connection strip on your furnace that the thermostat wires connect.

Coonect one lead from your multimeter to the C terminal or to the furnace sheet metal (ground). Measure the voltage to the R terminal and the W terminal and report that here.
The thermostat wires go directly into a wiring strip on a circuit board:

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Measuring there with the multimeter on 200 Vdc, C to W is 00.2 and C to R is 00.1.
 
  #18  
Old 11-11-12, 06:34 PM
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Did I post the right information? Should I have posted this issue in another forum?
 
  #19  
Old 11-11-12, 06:47 PM
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You did NOT follow seattle pioneer's instruction... Your furnace uses AC power not DC power.
 
  #20  
Old 11-11-12, 09:19 PM
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Ugh, I had to reread the entire thread several times before I caught my mistake. This is all new to me.

I measured it again with the multimeter on the right setting this time (I think)--200 Vac:

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You can see in the photo that there is one input for the red probe and two inputs for the black probe ("10A" and "COM"). I have the black probe connected to the input labeled "COM" in case that makes a difference.

With the black probe on C, C to W is 00.0 and C to R is 00.0. With the red probe on C, C to W is 00.2 and C to R is 00.0. (Since I wasn't sure which way to do it, I did it both ways.)
 

Last edited by Toddler; 11-11-12 at 09:41 PM.
  #21  
Old 11-11-12, 11:07 PM
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You can try disconnecting the green wire from the G terminal on the circuit board.

That might turn off the fan.


Also,

Please post the make and model of the circuit board, which should be printed on the circuit board..
 
  #22  
Old 11-12-12, 04:25 AM
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You have no secondary power at the terminal strip. Check the fuse on the control board. Beyond that you need to know why there is no power where there should be. This may be due to an open limit. Many integrated furnace controls turn on the blower when there is a problem within the system. It also looks like the blower wires on the control board may be burnt. They are red and blue and on terminals that say cool and heat. IF they are burnt you may want to shut off the power and remove the control board and look at the back of the board to see if you find anything burnt up.
 
  #23  
Old 11-12-12, 12:13 PM
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Thanks for all the advice, hopefully we are getting closer to narrowing things down.

The circuit board is a Honeywell Fan Control Board 1138-103. The fuse is good. I checked the terminals for the blower wires and the board on both sides and it looks fine, although I see there the terminals look a little discolored. Here are photos of the board:

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When I was done with this round of testing, I flipped everything back on and paid attention to what happened. It took about 60 seconds before anything happened at all, then I heard a couple of clicks and the blower started. Air is moving through the vents, but there is no heat, and there is no display on the thermostat--same as last week, so I took that as a sign that hopefully I haven't made matters any worse yet.

Forgive me for all the photos and details, I am just trying my best to make sure I give as much information as I can and that nothing gets lost in translation since this is unfamilar territory for me.
 
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Old 11-12-12, 02:18 PM
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Unfortunately, I'm not finding an operating manual for that circuit board.


I'd check to see if you have 24 VAC coming from the transformer.
 
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Old 11-12-12, 02:44 PM
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Here's the transformer, York 025-18452-700. With the multimeter set to 200 VAC, the transformer output measures 27.4 (measuring the red and green terminals on the 24V side, right?).

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  #26  
Old 11-12-12, 03:51 PM
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Yes, that's right.

Is there a circuit diagram on the furnace?

See if you can identify any parts connected between the transformer secondary (the 24 VAC) and the "R" terminal of the circuit board. Something has got to be preventing the voltage from getting between those two connections.

If you can post a good picture of the circuit diagram, that would be very helpful.
 
  #27  
Old 11-26-12, 01:54 PM
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I found the diagram. I'll attach photos at the end of this post.

The wire from the transformer secondary goes down a hole into a deeper part of the unit I haven't tried to access, but I am guessing I have to remove the entire top of the unit to do that. I would love to have confirmation that's the proper next step before I try, though.

Hopefully the diagram will help. I know they came out a little dark. I can correct them in Photoshop and email them if that would help.

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  #29  
Old 11-26-12, 02:13 PM
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Old 11-26-12, 02:21 PM
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Page 16...

Check
. Line voltage power Check
. Low voltage transformer Check
. Main limit
(Auto reset)
. Rollout limit
(Manual reset)
. Auxilary limit
(Manual reset)
. Thermostat
. Wiring
. Air proving switch on
combustion air
blower system
. Vent damper (if used)
is open and end switch
made
 
  #31  
Old 11-26-12, 03:32 PM
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Hmm, so reset the rollout limit and auxiliary limit? I'm trying to find where those would be. I'm looking for RS and LS on the diagrams, right? I see them but I have no idea what to look for or even where to look in the unit itself. Would those be in the gas/electrc service area or in the blower service area?
 
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Old 11-26-12, 03:47 PM
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When you find and reset them try to determine which one tripped and then refer to SeattlePioneer's first post...


Observe the sequence of events that occurs at the furnace when you turn up the thermostat and post that sequence of events in order and in detail.
The rollout should be at the burners..
 
  #33  
Old 11-30-12, 10:30 AM
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Paid a tech $82 to come diagnose the problem. Bypassing the rollout switch got the unit running again, but he said the CO levels were causing it to trip (440ppm). Said codes require him to shut the unit down due to safety reasons (200ppm is the limit for codes). Found a crack in the heat exchanger, and the cost for the part is about $3700, total repair would be $4200. So that ends my attempt at a repair.

A new Amana unit with 10 yr parts/10 yr labor/20 yr heat exchanger will run $5300 installed, so that's the new plan.

Thanks for all of the advice and guidance.
 
  #34  
Old 11-30-12, 11:31 AM
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Final question, I hope. I've been calling around, and here are my current options:

Broan R6GD (13 SEER) for $3800
Broan R6GF (15 SEER) for $4500
Rheem RRNL Classic 13 SEER for $5200
Amana APG13M (13 SEER) for $5300 (includes 10 year labor warranty, unlike the other units)

Any advice is appreciated.
 
  #35  
Old 11-30-12, 01:17 PM
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Unless someone here gives me reason for concern, I have decided to go with the Rheem RRNL Classic 13 SEER. Some price haggling brought it down to $4500.
 
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Old 11-30-12, 06:21 PM
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Rheem is a good product.
Impressive negotiating skills.

Does this unit have a service disconnect switch?
 
  #37  
Old 11-30-12, 10:54 PM
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If that's something I should have installed, now is the time.

Is a service disconnect switch the same as a breaker box? I've got the package unit for downstairs and a split unit for upstairs. Power to both is supplied by a breaker box attached to the house with separate breakers for each unit.

I just had the split system replaced in October. The installers got all the necessary work permits, and the city codes inspector came out and signed off on the job when it was through. Is a service disconnect switch a codes thing?
 
  #38  
Old 12-01-12, 05:49 AM
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Yes, a switch to turn off power and service the unit within a short distance from the unit is required by code in most places.

It can also save you the trouble of disposing of a toasted AC serviceman some day.
 
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Old 12-01-12, 06:31 AM
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A service disconnect for the gas unit may be as simple as a toggle switch within sight of the unit.
 
  #40  
Old 12-01-12, 11:25 PM
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Yes, I think both those things are installed. There's a toggle on the gas line and a breaker for the power. I've used these installers before, and they seem to do things almost excessively by the book.
 
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