Lennox Problems 3 ton roof top

[Ashlexall]

Just wondering if anyone could help me out. I don't know if it is dealing with my public school system today or what i am just mind dumb. I have a M# LCA036H2BB1G Lennox roof top that another contractor tried to repair by using a 17 year old and a phone. Once they found out i had been called they cut alot of wires. I replaced all the wires and have another problem. I can get the board lights to light for fan and cool 1, but nothing comes on. I check on the far right of the board were the 24v comes in to the board and the power is there but if i check the third wire over which goes to the comp. contactor there is nothing. I believe the board is fried, although I've never seen a board go through its processes and when i press and hold the reset button the compressor will come on for a second. I had one wire that was of that was not on any schematic. It was added as a feature and it looks as if it went to the economizer. It needed 24v to operate so i stuck it on the 24v terminal. does any one have a comment it would be greatly appreciated. The original problem was blown fusses and a trans????.

[heatingman]

Does it work in test mode?

[Ashlexall]

Nope, and it seems that you can not clear the codes unless their was been many errors. I reset codes for about 5 min. and it seemed to be mostly the same. E01 H10 H11 mostly pertaining to loss of power.

[kenadiens]

could it be that Y1 is your econo and your comp isn't getting the call on Y2?

[Ashlexall]

Could be, I have been taking care of this unit for two years along with this group of thugs. It has been running fine until some type of power failure. I personally think one of the relays on the board is fried. What do you think. I normally do not leave a unit down but since they have another I have to take care of some other things but I will be going back this afternoon .

[Jpaulsmith]

I would say it is the board. If your getting voltage in and nothing out the board seems to be fried.

[hvac wiz 79]

H10 & H11 are the heat test. I don't recall an E01 but know of S01 ... errors are numbers stored 1 through like 110 or so. what's the OD temp? OAD suitable LED illuminated?

[hvac wiz 79]

what makes you "think" a relay is fried? test it to know for sure.

[hvac wiz 79]

I would say it is the board. If your getting voltage in and nothing out the board seems to be fried.

wrong

[Ashlexall]

H10 & H11 are the heat test. I don't recall an E01 but know of S01 ... errors are numbers stored 1 through like 110 or so. what's the OD temp? OAD suitable LED illuminated?

I am assuming it is an e for error all I get is the bottom light on the code and it is a c. Thinking it is the bottom of a digital E. Od is about 75 room temp is 78f there is another led on on far right but have forgotten what it stands for. I believe it is omg org or something to that effect. The tstat is calling and the unit is lighting up just no function. No fan with tstat fan on no condenser fan when I push comp contactor on. I will be back on site in 3-4 hours and will check more options. I am not feeling to brain dead today.

[Jpaulsmith]

wrong

Assuming he has a call for cooling and getting 24volts from stat to Y1 input and he has checked pressure switches to be sure they are closed and still not getting 24 v to output for compressor contacts I would say its the board.

I'm assuming he has checked all of the safetys on the board.

[rednecktech]

I had a board on a JCI 10 ton acting all crazy and giving loss of power due to C1 wouldnt start but what i found was FS was bad . never gave that code ,just never closed contactor to C1 and then error of loss power

[slctech]

No such thing as a E01 on a Lennox IMC board. Like you said it is probably a c01 which means the unit is receiving a first stage call for cooling. Need to double check all the dip switch settings and will need to double check ALL the ECTO settings. Have a feeling that company XYZ was in there playing around and screwed up something in the ECTO settings. Older versions of the IMC may snap back to default on a power bump. If that is the case, may be getting a call for heat but the ECTO setting is basing itself on remote sensor and not conventional thermostat. Need a laptop and plug into the thing...SOOOO much easier. Takes special connections, but the LC program is free from Lennox can be downloaded from their commercial site.

[Ashlexall]

You know I looked at the dip switches but I thought no they would not do that. But hay if they would cut wires and disable a unit like they did I would not put it past them. You know I'm not a person that holds my tongue on stupidity. I meet one of these guys on a roof about 120 miles from here and was talking about another issue they made for me and how I solved it. He laughed and told me he was helping out in the area at the time. I told him he was an
Idiot and needed to find another line of work. Because of people like him is why we have issues.

[Perennial Student]

Personally, after the mickey-mousing they did, I would install a new board and a wiring harness. (or at least go through, repair and label and land every wire per schematic)

[Ashlexall]

Just wanted to update.
Found all cut wire. Found that when I jump the comp contact out on board comp runs same with cond fan . When I jump blower out it trips the trans fuss hence is why it was tripped when I arrived. Issolate board ( unplugg blower contactor ) it still tripped trans. I conclude it must be a shorted relay in board.

[timebuilder]

Just wanted to update.
Found all cut wire. Found that when I jump the comp contact out on board comp runs same with cond fan . When I jump blower out it trips the trans fuss hence is why it was tripped when I arrived. Issolate board ( unplugg blower contactor ) it still tripped trans. I conclude it must be a shorted relay in board.

I gotta tell you, I'm having trouble with this.

I work on these units a LOT, and I'm catching things that are not making sense to me.

Found that when I jump the comp contact out on board comp runs same with cond fan.

What do you mean by "jump the comp contact out on the board?"

What is a "comp contact," and where on the board is it located?

Do you have pictures you can post?

The first thing I would do is make certain that the "unit test" and "shift" DIP switches are to the LEFT.

Are they?

How are you "jumping" the blower out? Are you placing a jumper on the wires at TB1?

What does "unplug the blower contactor" mean? Where did you do that? Do you mean remove the coil wires from the contactor????

In cases like this, communicating accurately is CRITICAL to our being able to help you.

[Ashlexall]

I am sorry about the short terminology, i was riding and it hit me that i have not updated my findings. I was typing on my iphone and not a very good typist. I had to keep things short and sweet. I am sorry for the inconvenience.
On the right side of the board MI-7 Pt# 70M2101 there is a line of relays. Under these relays is were the 24v Comes into the board and powers the contactors for your Indoor blower, Condenser fan motor and the compressor. On the far right there is a red wire (24v) I put a wire in that wiring plug and jumped it to the I think 3rd or 4th wire to the left. This allowed the compressor contactor to engage. Then I went to the wire next to that one and it engaged the condenser fan motor. When i went over to the wire that was coming of that board and going to the indoor blower contactor it tripped the transformer fuss mounted on the transformer. I took the wires off of the contactor for the indoor blower motor because i knew that when i pushed in the contactor the Indoor blower would run. Although this does not count a shorted contactor out. So by taking the coil wires off of the indoor blower contactor i then issolated the indoor blower relay on the board. I then tried puttin power on the indoor blower relay on board and the transformer tripped again. Seeing how the wires coming of the board and going to the indoor blower contactor coil were off of the contactor. I came to the conclusion that the relay on the board or something on that board has some type of a short.
As far as i could tell all dip switches were to the left except the second down it was to the right allowing diagnostic codes to show I think don't hold me to that. But when I was there I made sure they were set the way the chart on the door said to set them.
Any thoughts let me know. The worst mechanic i know is a mechanic that thinks they know everything. I am a 41 year old second generation HVAC Mechanic that has seen and done a lot of things. But I still learn things. And forget. Its actually been about ten years since i have worked on anything this small. But after all they are all the same some just bigger.
Thanks,

[Ashlexall]

I am sorry about the short terminology, i was riding and it hit me that i have not updated my findings. I was typing on my iphone and not a very good typist. I had to keep things short and sweet. I am sorry for the inconvenience.
On the right side of the board MI-7 Pt# 70M2101 there is a line of relays. Under these relays is were the 24v Comes into the board and powers the contactors for your Indoor blower, Condenser fan motor and the compressor. On the far right there is a red wire (24v) I put a wire in that wiring plug and jumped it to the I think 3rd or 4th wire to the left. This allowed the compressor contactor to engage. Then I went to the wire next to that one and it engaged the condenser fan motor. When i went over to the wire that was coming of that board and going to the indoor blower contactor it tripped the transformer fuss mounted on the transformer. I took the wires off of the contactor for the indoor blower motor because i knew that when i pushed in the contactor the Indoor blower would run. Although this does not count a shorted contactor out. So by taking the coil wires off of the indoor blower contactor i then issolated the indoor blower relay on the board. I then tried puttin power on the indoor blower relay on board and the transformer tripped again. Seeing how the wires coming of the board and going to the indoor blower contactor coil were off of the contactor. I came to the conclusion that the relay on the board or something on that board has some type of a short.
As far as i could tell all dip switches were to the left except the second down it was to the right allowing diagnostic codes to show I think don't hold me to that. But when I was there I made sure they were set the way the chart on the door said to set them.
Any thoughts let me know. The worst mechanic i know is a mechanic that thinks they know everything. I am a 41 year old second generation HVAC Mechanic that has seen and done a lot of things. But I still learn things. And forget. Its actually been about ten years since i have worked on anything this small. But after all they are all the same some just bigger.
Thanks,

[timebuilder]

Okay. I'm down to a couple of questions.

1) Because wires were cut by the other guy, I would use the diagram to physically trace the wires going to the blower contactor from the board connector plug, to make sure the short is not in the wiring repair.

2) I would remove the blower coil wires from the contactor and

a) measure the coil resistance, and compare it to a known good coil, usually between 8 and 10 ohms on a multimeter.

b) using TB1, the contact strip in the left hand side of the blower compartment, jump R to G.

If you have not opened the blower door and investigated this area, do so, because they may have done something there, too. You can find a reference to TB1 on the sticker inside the door, and the connection numbers are shown vertically and somewhat out of order. There are little numbers inside squares that indicate the terminal numbers of the strip. Find the function you want (R, G, Y1, etc) and its associated number, and go from there.

Having checked TB1, and jumped R to G, apply power to the unit with the blower contactor coil wires disconnected from the coil terminals. If you have an ammeter with an "inrush" button, you could put it on the 24 volt power feed to the board and see how much the current spikes.

Before ordering an expensive board, I would pull it and look at it very carefully, in good light and with reading glasses on if you use them. Look for any damage, discoloration, or lifted circuit traces on both sides.

With the board out of the unit, use solid hookup wire to connect the incoming 24 volt feed that enters the board, and connect it to the blower output wire that goes to the contactor. Create a ground path for the contactor coil, and try to use the wiring harness as a part of it. Connect the coil and power up the unit, with your TB1 jumper R to G still in place. Does the blower coil pull in, and the breaker hold?

If "no" for the breaker remaining closed, after all this testing, I might be inclined to order a board. If I was onsite with you, I could probably become inspired to make some additional tests, but at this level of distance from the situation, I'm not sure what those tests would be. I'm only unsure because wires were cut, and more than one tech was in there. Truthfully, I'm the kind of guy that would want to hand-trace every wire that connects to that board, and ensure the repair integrity and routing, because a couple of hours of my labor is pretty inexpensive when compared to that controller.