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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 8767
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I have a Lennox HVAC dual zone with a damper control board

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I have a Lennox HVAC dual zone with a damper control board with 4 relays on it and 5 connections labeled stat1,stat2,damp1,damp2 and furnace. The original symptom was that when the upstairs thermostat was on, the AC compressor outside would not kick on. If I turned it off, and turned on the downstairs tstat, the compressor would run. A tech came out and said the board was bad, wired both dampers to damp2 and said only use the upstairs tstat. That seemed ok for awhile (although no zone control) but now the compressor still doesn't run some times. It seems to kick on and off at will. Is that an indication of that damper relay board being bad.

Hello, this situation you have here is complex and will likely take hours and some skill on your end to diagnose. There is not a simple answer other than 'its a controls problem and also possibly a dirty condenser coil or bad outside unit fan motor'

I am not the only expert here, you can choose to rate my work or opt out and see if anyone else here will go that distance with you.


Important note about RATING my work:

I am a retired mechanical engineer and HVAC/electrical/ refrigeration and boiler contractor... with 56 years in this business. The last 20 of those years consulting for major firms nationally..


All I ask is please select the***RATING LINK***at the top of your page, that is the only way I am credited through the site. Rating does not affect your charges nor ability to refund if not satisfied.


If you need to be coached through a full diagnosis/repair,and wiring etc. for up to two days, and wish to be trained to use test instruments...... that goes well beyond' Just a simple Answer' of course, and goes beyond what most other experts here offer.....rate my simple answer so far positively.. and I will deliver that training and coaching to you All on the same dime soto speak.


Lacking a positive rating I can spend days helping a person at my own expense and loose my shirt,shorts and socks on the deal.


Attach a close up photo of the wiring diagram glued to the inside of the blower access door and I will mark it up with troubleshooting instructions then follow up with step by step training and coaching until you have a solution.


Photo must be exceedingly well focused. Use the 'add files' link next to your send button to get the photo to me.


Phone call offers:

If you wish to accept the companies $25 phone call offer,if indeed they send you one, this will go a *lot faster, but it IS 100% optional... or we can continue here in this dialog box at no additional charge.

Phil and other HVAC Specialists are ready to help you
Customer: replied 2 months ago.
I would like to pursue this further. At least some basic steps to try and determine the cause. I'm unable to attach the file though. Is there another way to send it?


I will coach you through this in detail.. not just a few hints etc

Are loading the picture of the zone control panel into your computer, then going to this dialog box and clicking on the 'add files' link?

Customer: replied 2 months ago.
Thanks for the quick response. When I click add files nothing happens. Tried IE and Chrome.

Try using the paper ciip icon at the right end of the tool bar at the top of this dialog box

and tell me you are tying this from a smart phone, or computer and if its an apple brand

Customer: replied 2 months ago.
BTW, it's hot here and it seems to be DOA. If I can just bypass that damper board to see if that resolves it would be great. The add files just opened my file explorer. Hopefully you have it now.

I got the diagram, give me a few minutes to mark it up with trouble shooting instructions,

I also need a photo of zone control panel with its door open showing all of the wire connections

Customer: replied 2 months ago.

Test #1 Next time the system fails to come on in cooling mode, when it generally does come on in in cooling mode, jumper R to T at the thermostat terminal strip on the printed circuit board inside the furnace,

Click here please

IF the AC suddenly comes on, we know for sure that the problem is with the zone control panel or one of the attached thermostats,

IF the AC does not come on, measure the voltage between R and C if you have 24vac there and the AC does not come on, with the jumper between R and Y in place then we know the problem is with the printed circuit board, or the outside unit.

(never jumper R to C that will blow the 3 amp fuse on the printed circuit board)

Ooops Jumper R to Y not R to T (there is no T)

Customer: replied 2 months ago.
Great, it's not coming on so I'll try it now. Jumper R to Y on the board with all the relays (2nd photo) that goes to the furnace unit, correct?

Yes try the R to Y jumper there but also to be 100% sure, jumper as shown on the wiring diagram inside the furnace (Yellow jumper wire shown)

Customer: replied 2 months ago.
Ok, that kicked on the outside unit and it did stay on once I removed my jumper although I don't know that it will stay on.
Customer: replied 2 months ago.
Anything I can do to make sure it comes back on once it reaches temp and kicks back on? Also, what board would be a good replacement for that old one? I can't find those online anywhere.

We can stay on that path for a while to see how it works out and if the jumper once again starts the AC

That is about the oldest zone control set up I have ever seen, replacing the entire zone controller will be a good idea, including the thermostats

click here please

Customer: replied 2 months ago.
Lol....the house is only 17 years old but it is the original HVAC. So leave the jumper on permanently until I can replace the board?

The jumper is for testing only, do not leave it in place, but you can use it to manually run the AC to cool the house down, then remove it

Click here for how to wire the new Honeywell HZ311 zone control panel,

17 years when it comes to electronic controls is about like a 17 year old computer.. workable to some degree but obsolete when it fails

Those are 4 wire damper motors... I have to see if they will work with the HZ311

Can you get me the brand and model number of the damper motors.

Customer: replied 2 months ago.
TrolAtemp Model MST 24v 6 w 93-057H-001
Anyway to bypass that damper where the unit will kick on until I get another board? It quit on me again.
Customer: replied 2 months ago.
I have to run and get another fuse. I must have touched the blue wire. Thanks so much for your help and hanging with me this time of night. I really appreciate it. I'll check the response when I get back.

Click here for the wiring diagram needed to make the existing dampers work with the Honeywell HZ311 zone control panel diagram is lower left on page 2 only 3 wires needed

Click here for the wiring diagram needed to make the existing dampers work with the Honeywell HZ311 zone control panel diagram is lower left on page 2 only 3 wires needed

Stay in touch as needed

Customer: replied 2 months ago.
Thanks again. So no way to bypass until I get a new board? Can the thermostat wire directly to the board in the furnace?

Good idea, yes you could wire one of the thermostats directly to the furnace terminal strip... in that case however you would have to manually open both dampers, there should be a manual open lever on them,

Let me know if you can find the levers or not

I need a photo of the damper and its linkage,... we would disconnect the linkage and use duct tape to hold it in the damper open position

Customer: replied 2 months ago.
My phone died but it just has a little arm that rotates around. I can just clamp it in its current position. So connect the stat wires color->color on the furnace terminal strip? I'll give it a try since it seems to be cutting out a lot more now.

If it is cutting out with R and Y jumpered then the problem is most likely with the printed circuit board inside the furnace

That said, I would replace the old zone controller on principle

You also need to be sure the the condenser coil on the outside unit is clean

click here, you can buy the ac coil cleaning kit at Home depot, thats the best, ***** ***** some other larger hardware store