Lennox AC (10ACB) TurnsON /no Blower working on Furnace.

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  #1  
Old 08-22-14, 06:24 PM
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Lennox AC (10ACB) TurnsON /no Blower working on Furnace.

Lennox 10ACB36-5P (1997)
Furnace is Coleman Evcon Model BGU10016A
Thermostat Hunter Air Temp Plus Model 44422

I just turned my AC on for the first time in a year. The Lennox AC seems to be working fine outside the house. The fan on top of the AC is running smoothly and the unit seems to be running at normal speed. Inside, the ducts on the furnace are getting cold but the blower in the furnace to blow the cold air throughout the house is not working. I've left it on for an hour, no luck. Now, If I turn the furnace on to heat... the blower works blowing, heat throughou the house. Just the AC can't get the blower to work in the furnace. Any help would be appreciated. I have all the manuals for the Lennox and my logic leads me to believe it might be the Start Capacitor C7, or the Potential Start Relay K31.

I'm a newbie here and hopefully I can get help and give it in the future.
 
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Old 08-22-14, 06:52 PM
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I've seen this before but I am only going by memory. In heat mode the fan is started by the heat sequencer. In cooling mode the fan is started by the green wire from stat. This pulls in the blower relay. So it could be a bad relay or the stat is not working correctly.
 

Last edited by skaggsje; 08-22-14 at 07:07 PM.
  #3  
Old 08-22-14, 06:53 PM
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Sounds like the control board in the gas furnace to me.
Bet you can bypass the board and run the cooling speed of the blower.
The back side of the control board probably looks burned behind the small black relay soldered onto the board.

This diagram shows a gas furnace.
http://www.searspartsdirect.com/part...&prst=&shdMod=

I would price check Amazon if you can prove the board has failed.
Post some pics...
www.photobucket.com
 
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Old 08-22-14, 07:41 PM
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If it is the board I don't think I can test it. By looking at the parts list from sears it looks like I would need #13 Furnace Control Board... Correct? If I had to call a furnace man they would charge $80 to come out and then the price of the board with some extra built in. I know I could probably replace the furnace control board without any problems by myself. Everything is original since 1997.
 
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Old 08-22-14, 07:59 PM
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\

I usually unplug the black wire to the fan and plug it to the L1 terminal along with the black wire providing power to the board using a Y connector.

You have not posted a picture of your control board or of your diagram so I cannot say with any certainty that your high speed fan wire is black or that your power terminal is labeled L1.

Jumping R to G as Skaggsje has posted to prove that your control board is even getting the signal would be an advisable first test.
 
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Old 08-22-14, 08:15 PM
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Ok I've attached the photo... Did it work?
 
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Old 08-22-14, 08:52 PM
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You should be able to trace power from the door switch (highlighted red)to L1.
You should be able to trace the fan motor wire (green box) to the cool speed tap.

The large relay highlighted yellow is probably burned on the backside of the board.
 
  #8  
Old 08-22-14, 08:53 PM
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Ok I did something and this seemed to work.

Ok... I'm getting somewhere. I turned the tstat from auto to fan. The fan worked. Then I turned on the AC. The AC is working and pumping air through the registers. Now I turned the fan only to AUTO... and the air is still on and the blower is working. I then turned off the AC totally. Switched the fan to AUTO and turn on the Air Again. Its working.

What does that mean? Do I need a new Thermostat?
 
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Old 08-22-14, 09:34 PM
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It sounds like the AUTO / FAN ON switch may be corroded or intermittent.
Could be time for a new stat.
 
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Old 08-26-14, 04:24 PM
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I want to change the thermostat. I contacted Honeywell about their Wi Fi Thermostats. Two of them...

Honeywell Wi-Fi Smart Thermostat with Voice Control
Honeywell Wi-Fi Smart Thermostat with Voice Control - Programmable Household Thermostats - Amazon.com
Honeywell Wi-Fi Smart Thermostat
Robot Check

I sent them the pic below and this was the response I received from them. I guess I didn't get a positive answer... and I don't know really how to identify his answer. Any suggestions?

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Good afternoon,

Thank you for sending in the photos. There is one wire missing that I'm not able to see from the photo if you have or not, and that would be a wire on the "C" terminal, it could also be labeled "24v" or "com". This wire is a requirement for the WiFi thermostats. But if you have this wire then yes you have everything you would need for your thermostat.
I hope this information was useful to you, if you have any other questions or concerns or I can be of any further assistance please let me know.
Thank you and have a great day,
 
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Old 08-26-14, 04:40 PM
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From the photos, it appears that you don't have a common wire being used. However, if you have any unused wires in the thermostat wire bundle, you could add one, all you would need to do is to connect an unused wire to the air handler common. You need to strip back the outer jacket of the thermostat cable and see if there are any additional wires contained within the bundle. If there are, you're in luck. If there aren't any spare wires and you want a WiFi thermostat, you'll have to run an additional thermostat wire, or replace the existing thermostat cable with one with more conductors.
 
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Old 08-27-14, 11:40 AM
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Thanks so far... I'm almost there. Now Its obvious I don't have the 5th C wire. I want to add another wire from thermostat and run it to the furnace. I can't get a hold of Coleman (Seems they are on an Extended Lunch Hour). I've included a pic to help you help me do the right thing here. I've traced everything correctly in showing the Thermostat and the AC wire. Tried my best in filling in all the blanks with the illustrations. Next to the 1-5 screws I have showed the color of the wire that is attached to each screw from the thermostat. Where should I attach the C wire that I am going to add to the new thermostat? What type of wire/guage should I get from Home Depot?

1=White/Gray
2=Green
3
4=Red
5=Blue


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Thanks again for everyones help here in the forum?
 
  #13  
Old 08-27-14, 12:20 PM
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If you can find the 24VAC transformer, the common is one side of the transformer output, the other side should go to the Red thermostat lead. The transformer supplies the 24VAC power for the thermostat and the control lines (heat, cool, blower). Usually, the common is tied to the metal frame/chassis of the furnace/air handler. To confirm this, take your voltmeter and try reading AC volts from the red thermostat wire to the chassis. If you read ~24VAC, then the common is tied to the chassis. If this is the case, you can attach the common wire to anywhere on the metal chassis. There is relatively little current required by the thermostat. 22 gauge or heavier wire is sufficient.
 
  #14  
Old 08-27-14, 12:25 PM
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The terminal that you have marked as #5 is the common.
 
  #15  
Old 08-27-14, 01:01 PM
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Slowly things are making sense... but I see the wiring diagram on the furnace lid. Heres what it looks like.

@skaggsje... The wiring diagram shows C(3) not 5 as the common. If so, is 3 the common?

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  #16  
Old 08-27-14, 01:42 PM
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Looking at the wiring diagram, it appears to me that terminal #3 (C) is the common. The two wires going to the outside unit should connect to terminals #3 (C) and terminal #5 (Y). To run a Common wire to the thermostat, connect it to terminal #3.
 
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Old 08-27-14, 01:46 PM
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If the diagram you posted is accurate then terminal 3 is the common. The common wire comes directly from the low voltage side of your transformer and then to the control board and eventually goes to your condenser outside. The diagram shows it as a gray wire but if the transformer has ever been replaced the wire color will more than likely be different. It is important to follow the low voltage wires coming out of the low voltage side of the transformer to see where they are connected.. One of these wires is the common (C) and is the one you need to determine where it connects. I used red on your diagram because gray doesn't show up too good. You can use a multimeter to test between the R and C terminals on the control board to see if you get 24V between them. You should definitely be able to use that C terminal to send to your new thermostat. If the control board was ever replaced then the terminal designation may have changed from the diagram you posted. The control boards normally have letter designations such as C, R, Y, G and etc to identify their function. When tracing, removing or installing wires make sure you turn off power to the unit. Do you have the model number for the control board currently installed?
 
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  #18  
Old 08-27-14, 03:10 PM
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According to the module the 5 should be the common. But yes the drawing shows 3 as common. Look just to left of terminals on the module to see the letters R, G, C, W and Y.
 

Last edited by skaggsje; 08-27-14 at 03:18 PM. Reason: correction
  #19  
Old 08-27-14, 03:34 PM
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Ok This is what I think is the serial number of the motherboard.

PC-A-P86A-94V0


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Heres the pic. Its on the bottom right corner of the board, opposite the Tstat Screws.
 
  #20  
Old 08-27-14, 03:35 PM
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I understand what you are saying. The questions that still remain: 1. Is the control board installed now the original or a replacement 2. Is the diagram you have posted the correct one for the control board that is installed now or 3, Is it the original wiring diagram that shows wiring for the original. The control board installed now has the correct terminal designations and is what should be followed. Of course, a person would use the original wiring diagram to properly install a replacement control board (if it was in fact ever replaced). I hope I didn't confuse you on what I am trying to say.
 
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Old 08-27-14, 03:43 PM
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The motherboard has never been switched out. Its about 15 years old. I'm Original owner. The only difference I see is that the builder used a blue wire rather than a yellow wire in his installation. I haven't ever had any problems with this before, just changing out the humidifier filter a couple years ago that was causing the furnace to shut off before the blower kicked in (blocked airflow). There is a General Power humidifier on this too.
 
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Old 08-27-14, 03:57 PM
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I believe the number you provided, PC-A-P86A-94V0, is the number for a circuit board part number and not the part number for the actual control board. If you get a chance please look for other numbers. Knowing that is the original board will help in identifying the terminals.
 
  #23  
Old 08-27-14, 04:09 PM
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Where would you find this number. I looked all around and couldn't find anything else that I would think it would be. If its on the other side, then I haven't taken it out.
 
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Old 08-27-14, 04:20 PM
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This is the only thing I could find on the bottom of the board.

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Old 08-27-14, 04:38 PM
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I did some research and believe I have found the answer for you. While I was searching, you posted the correct number of the board. I found two photos of boards with part number 2702-310 that shows the middle terminal is indeed the C terminal. I have attached the two photos. Based on these photos and your wiring diagram I believe the middle terminal marked C in the two photos attached is the one you will want to run your wire to from your new thermostat.
 
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Old 08-27-14, 04:55 PM
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Thank you... The board below the top one (less focused pic) is the board I have simply by the arrangement of the TSTAT screws. I'll go out and get a 24v wire from Home depot and do what I have to do. Is there a color I should look for? I was just thinking a single black one. If I do decide to get a 5 wire strand (Might be simpler to pull through wall aattached to the old one), what colors or type should I get?

Also I couldn't find anywhere near the screws the lettering for colors. Its just not there.
 
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Old 08-27-14, 05:13 PM
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I always advise to get more conductor wires in a thermostat cable than you actually have a need for at the moment. That is so you will have some extra wires for future use and in case a problem develops such as a nail or screw damaging one of them. Yes, if the original thermostat cable is not stapled to the house framing you can tape the new one to the old and pull it through. As far as wire colors, I would try and use the colors shown in the wiring diagram you posted as much as possible. The most common thermostat cable wire colors are red, green, yellow, blue, black, brown. I usually use blue for the common wire.

For you information: while researching your control board I found some other part numbers for the control board. ICM Controls ICM2801 and York Evcon Coleman Furnace Control Board 7990-319P. These numbers may be of benefit to you in the future.
 
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Old 08-27-14, 06:04 PM
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Thanks again everybody for your long patience with me. I thank you all for the input. I'm pretty sure everything will work out thanks to you guys.
 
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Old 08-27-14, 06:43 PM
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Please let us know the outcome as it may help others in the future. Good luck!
 
  #30  
Old 08-29-14, 11:10 AM
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Hi I believe that I have this same exact circuit board and need to have mine replaced. I am trying to order a replacement but there are (3) EVCON part numbers listed on the board and I can't determine which one to use. The numbers are:
* 2702-310/A (green)
* 7956-319 (blue)
* 7990-319 (red)

Can someone tell me which number I should use to order my replacement board?

Thanks,
Dave
 
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Old 08-29-14, 11:17 AM
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It is always best to find the actual number on the board and then match it exactly, if possible. Are you saying the board you need to replace has all of those model numbers you listed written on it?
 
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Old 08-29-14, 11:26 AM
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Yes that is exacty what I'm saying. Here are 2 pics of the board showing the 3 part numbers.
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  #33  
Old 08-29-14, 12:18 PM
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Here is another pic of another part of the board with more details on the green, blue, red (I think). Do you know what the difference in the colors after the part numbers mean?

When I get home tomorrow I will get the part number for the overall furnace if that will help more. Any other thoughts for now?

Thanks again,
Dave

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  #34  
Old 08-29-14, 01:58 PM
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On the older control boards it is pretty common to see two or three different part numbers. As far as the colors shown after the numbers, I really don't know but I think it might be the color of the status light. Any of the part numbers shown on the board should work, if you can find them. As I posted earlier, ICM2801 and 7990-319P are other numbers I cross-referenced to 2702-310/A.
 

Last edited by firedawgsatx; 08-29-14 at 02:15 PM.
  #35  
Old 09-01-14, 04:00 PM
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Thanks for the response. I am home now and found the part number of the overall furnace. It is listed as:

- EVCON INDUSTRIES, INC
- Model No: BGU07512A

Based on this info, would you still suggest the replacement to be ICM2801 or 7990-319P?

It is quite old (from '97) and it will need to be replaced very soon but right now the board is the only thing wrong so I want to replace it and delay the big purchase.

Thanks for any help you can provide!
 
  #36  
Old 09-01-14, 05:03 PM
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Here is a link to a manual for your unit:

http://www.hamiltonhomeproducts.com/...001-D-0403.pdf

According to the parts list the most current number integrated control is 031-01933-000. Other numbesr I found are 2702-310P and 43101972100. Since your system, as you mentioned, is quite old the original parts numbers are obsolete and change throughout the years and the item can be extremely difficult to find. The "upgrade" control boards that replace all of the obsolete part numbers have wiring harness adapters to work the older systems. Based on the numbers shown on your board, the numbers I posted earlier should work. Whichever part number you decide to go with, I would have the person who is selling it verify it is the correct part number for your application. It definitely pays to shop around as prices vary considerably.
 
  #37  
Old 09-01-14, 05:14 PM
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Wow - that is great info thank you! I hate to keep asking questions this should be my last. I am looking at this part number and while a bit expensive it seems to be the correct one. Although it is not the replacement part number you suggested. What do you think?

York Coleman Control Board 2702-382P/A 2702-310P/A

Thanks,
Dave
 
  #38  
Old 09-01-14, 05:21 PM
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Actually, that is one of the part numbers I listed as shown in the item description (43101972100) . Yes, according to the data, it should work. Just have the company verify it based on your model number and the numbers you found on the board. I am sure you can find that particular board for a better price.
 

Last edited by firedawgsatx; 09-01-14 at 05:43 PM.
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