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We have a Lennox Ch33-36a-2f and it was not working but the

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fan came on in manual.....
We have a Lennox Ch33-36a-2f and it was not working but the fan came on in manual... We figured out from the diagnostic codes light 1 was slow flashing and light 2 solid... We changed the filters. Turned off for 30+ minutes and now no lights and fan does not come on when thermostat set to fan on. What should we try now?
Submitted: 1 year ago.Category: HVAC
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1/27/2016
HVAC Technician: Tim H., HVAC Professional replied 1 year ago
Tim H.
Tim H., HVAC Professional
Category: HVAC
Satisfied Customers: 3,971
Experience: Experienced in all aspects of HVAC, both residential and commercial.
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Hi, I'm Tim and I'm an HVAC expert here to assist you with your questions. Please provide all information I request as it makes it more difficult to troubleshoot something when I'm not there onsite. Essentially, you become my eyes and ears. Thanks for the opportunity to help. At the end of our dialog, you will have a chance to rate my service, but please wait until we are finished and you're satisfied you have all the information you need. Please be patient as many times we work with several customers at once.

Can I get full furnace model number, please, so I can look up codes? The number you provided, CH33-36A is your coil.

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Customer reply replied 1 year ago
Lennox G40UH (X) series is the number on the manual. Does that work?
HVAC Technician: Tim H., HVAC Professional replied 1 year ago

Diagnostic light #1 flashing and #2 on solid?

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Customer reply replied 1 year ago
that's correct.
HVAC Technician: Tim H., HVAC Professional replied 1 year ago

This would indicate:

Primary or secondary limit switch open. Limit must close within 3 minutes or unit

goes into 1 hour Watchguard. Check your flame rollout switches to see if they tripped. These would be small disc shaped switches in by the burners. They have a small red reset button in the center.

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Customer reply replied 1 year ago
should we press the button? This was the condition a while ago.... Now there are now lights on. Should we still go press the red button?
HVAC Technician: Tim H., HVAC Professional replied 1 year ago

Could also be the pri***** *****mit. Is the fan running continuously?

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Customer reply replied 1 year ago
No it's not running now
HVAC Technician: Tim H., HVAC Professional replied 1 year ago

Check your blower. Maybe the blower motor is bad causing it to trip out on the limit.

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Customer reply replied 1 year ago
The blower was running but after we turned the unit off no lights no blower. We turned it off by unplugging it.
HVAC Technician: Tim H., HVAC Professional replied 1 year ago

Unplugging it?

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Customer reply replied 1 year ago
it has a plug (grey one) that runs to the furnace and we thought to reset it by unplugging it. I can take a picture and send it.
HVAC Technician: Tim H., HVAC Professional replied 1 year ago

Hmmm, unusual for a furnace to have a plug in cord.

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Customer reply replied 1 year ago
Ours does. I can send a picture if that helps.
HVAC Technician: Tim H., HVAC Professional replied 1 year ago

Well, lets plug back in and see what happens.

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Customer reply replied 1 year ago
Hello?
HVAC Technician: Tim H., HVAC Professional replied 1 year ago

Well, lets plug back in and see what happens.

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Customer reply replied 1 year ago
Done that and now we have no lights and nothing is working.
HVAC Technician: Tim H., HVAC Professional replied 1 year ago

Check and make sure power switch is on, blower door on securely. Turn thermostat fan switch to On instead of AUTO, see if blower runs.

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HVAC Technician: Tim H., HVAC Professional replied 1 year ago

If nothing, check breaker. Maybe it tripped.

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Customer reply replied 1 year ago
Where is the power switch?
HVAC Technician: Tim H., HVAC Professional replied 1 year ago

Should be right by the unit looks like a light switch

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HVAC Technician: Tim H., HVAC Professional replied 1 year ago

You may not have a power switch if you have this plug in cord.

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HVAC Technician: Tim H., HVAC Professional replied 1 year ago

Very unusual for a furnace to have a plug in cord, by the way.

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Customer reply replied 1 year ago
I figuring that... Give me second and I will give you an update
Customer reply replied 1 year ago
No light switch. Our unit is in the attic and is horizontally mounted.
HVAC Technician: Tim H., HVAC Professional replied 1 year ago

Did you check circuit breaker?

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Customer reply replied 1 year ago
it's on.
HVAC Technician: Tim H., HVAC Professional replied 1 year ago

Check the plug in that you are plugging it in at. Make sure it has power.

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HVAC Technician: Tim H., HVAC Professional replied 1 year ago

If the plug in has power, next check the fuse on the control board. See if it's blown.

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Customer reply replied 1 year ago
Plug has power checking fuse now
Customer reply replied 1 year ago
Fuse is good
HVAC Technician: Tim H., HVAC Professional replied 1 year ago

If fuse seems OK, then the LED's should be slow flashing.

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Customer reply replied 1 year ago
No LEDs are not flashing.
HVAC Technician: Tim H., HVAC Professional replied 1 year ago

Get a voltmeter, check from C or common on board to R. Should be 24 volts AC. This will be on terminal strip where all the thermostat wires attach.

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HVAC Technician: Tim H., HVAC Professional replied 1 year ago

Make sure blower door switch is pushed in when you do this.

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Customer reply replied 1 year ago
Getting meter now
Customer reply replied 1 year ago
Still working on it
Customer reply replied 1 year ago
No not 24 volts getting 0
HVAC Technician: Tim H., HVAC Professional replied 1 year ago

Did you push in blower door switch while taking reading?

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Customer reply replied 1 year ago
Ok getting 5.2 volts when push in switch. Also getting buzzing noise when push in switch.
Customer reply replied 1 year ago
Pic attached. Where is the limit switch?
HVAC Technician: Tim H., HVAC Professional replied 1 year ago

Did you see the picture I attached? About the size of a playing card, two wires attached. Sits on the upright portion above the burners.

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Customer reply replied 1 year ago
saw the pic but it doesn't look like ours. That's why I sent the picture of ours
HVAC Technician: Tim H., HVAC Professional replied 1 year ago

Doesn't matter how many burners. The limit will look the same.

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Customer reply replied 1 year ago
Do you have a part number?
HVAC Technician: Tim H., HVAC Professional replied 1 year ago

It is a brown flat piece of plastic with two wires attached. About the size of a playing card.

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Customer reply replied 1 year ago
We found it.
Customer reply replied 1 year ago
It's done power back on. What should happen?
HVAC Technician: Tim H., HVAC Professional replied 1 year ago

Turn furnace power off, Take the two wire leads off the pri***** *****mit and tape them together, then power back on. The pri***** *****mit can be seen in this picture:

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Customer reply replied 1 year ago
Ok did that. Now what?
HVAC Technician: Tim H., HVAC Professional replied 1 year ago

See if you now have 24 volts across C to R

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Customer reply replied 1 year ago
No do not still 5.2
HVAC Technician: Tim H., HVAC Professional replied 1 year ago

Not making sense. You must have a burned out transformer, then.

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HVAC Technician: Tim H., HVAC Professional replied 1 year ago

Transformer may look similar to this.

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HVAC Technician: Tim H., HVAC Professional replied 1 year ago

You do have voltmeter set to volts AC, not DC correct?

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Customer reply replied 1 year ago
Y s set to AC. Is that the part we need? The exact one?
HVAC Technician: Tim H., HVAC Professional replied 1 year ago

No, just an example.

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HVAC Technician: Tim H., HVAC Professional replied 1 year ago

ON board, find the terminals XFMR-H and XFMR-N. Check across these for voltage. Let me know what you have. Make sure blower door switch is pushed in.

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Customer reply replied 1 year ago
Ok give us a minute
Customer reply replied 1 year ago
Do we keep the limit switch wire disconnected?
HVAC Technician: Tim H., HVAC Professional replied 1 year ago

Previously you taped the metal ends of the two limit wires together. Leave this way for now.

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Customer reply replied 1 year ago
125v
HVAC Technician: Tim H., HVAC Professional replied 1 year ago

OK, so we know the transformer has 120 volts on primary side, but only 5.2 volts on secondary side (according to the reading you gave me). So I would replace transformer if board fuse is not blown. I am going to be logging off here for tonight in about 5 minutes.

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Customer reply replied 1 year ago
Ok. Do you do service calls to Azle tx if the transformer doesn't fix it?
HVAC Technician: Tim H., HVAC Professional replied 1 year ago

There are many sites that sell Lennox parts. www.cozyparts.com is one of them. No, Just Answer does not do service calls. Sorry! LOL

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Customer reply replied 1 year ago
Thanks for your help. Anyway we can get in touch with you again if we need?
HVAC Technician: Tim H., HVAC Professional replied 1 year ago

Let me know if you have additional questions. Otherwise, good luck! Thanks for using Just Answer and please don't forget to rate my service as that's how experts get paid (thanks in advance for any bonus left). Otherwise experts work at their own time and expense. Feel free to post back with any additional questions.

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Customer reply replied 1 year ago
Anyway to get in touch with you again?
Customer reply replied 1 year ago
Do we get s case number?
HVAC Technician: Tim H., HVAC Professional replied 1 year ago

Just bookmark the page.

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HVAC Technician: Tim H., HVAC Professional replied 1 year ago

Bookmark the page and come back to it. As long as you have rated me positively, I will continue to work with you should you need further assistance.

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Customer reply replied 1 year ago
We have ordered the part and it comes in tomorrow. We are very happy so far and have every intention of rating (fantastically) you once we are done.... Keep tuned!
HVAC Technician: Tim H., HVAC Professional replied 1 year ago

Thanks for the update.

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Customer reply replied 1 year ago
Good afternoon. We installed the new transformer and we are still getting the same readings and still I lights. What's next?
Customer reply replied 1 year ago
Still no lights. What's next?
HVAC Technician: Tim H., HVAC Professional replied 1 year ago

Doesn't make sense. If you are getting 120 volts on PRI1 and PRI2 then you should get 24 volts at SEC1 and SEC 2

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HVAC Technician: Tim H., HVAC Professional replied 1 year ago

Here's what I want you to do. Check the fuse again on the board. Pull it out and make sure it is not blown. If this looks OK, turn furnace power off, and go to furnace control board. It may be mounted on a bunch of white "stand-offs". Loosen these and CAREFULLY turn it over, examine the back Look for burned marks or signs of overheating.

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Customer reply replied 1 year ago
Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Live Phone Call. Let me know if you need more information, or send me the service offer(s) so we can proceed.
Customer reply replied 1 year ago
The request for phone call was a mistake my phone was freezing.
HVAC Technician: Tim H., HVAC Professional replied 1 year ago

Board shows obvious signs of burned marks/overheating. Since we now know transformer is good, the board is the only thing between transformer and R-C reading 24 volts. If you can get me full furnace model number I can get the replacement board part number for you.

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HVAC Technician: Tim H., HVAC Professional replied 1 year ago

I show part # ***** Found one here. But you may want to check around for better prices.

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Customer reply replied 1 year ago
One more question. What would make the board burn up. I don't want to replace if it will just burn up again. What can I test or check. Thank you for your help!!
HVAC Technician: Tim H., HVAC Professional replied 1 year ago

It doesn't have to be any one thing. Boards go bad all the time. Remember, this furnace is not exactly new.

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HVAC Technician: Tim H., HVAC Professional replied 1 year ago

Let me know if you have additional questions. Otherwise, good luck! Thanks for using Just Answer and please don't forget to rate my service as that's how experts get paid (thanks in advance for any bonus left). Otherwise experts work at their own time and expense. Feel free to post back with any additional questions.

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Tim H.
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