How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Tim H. Your Own Question
Tim H.
Tim H., HVAC Professional
Category: HVAC
Satisfied Customers: 3971
Experience:  Experienced in all aspects of HVAC, both residential and commercial.
27228809
Type Your HVAC Question Here...
Tim H. is online now
A new question is answered every 9 seconds

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

Customer Question

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
Expert:  Tim H. replied 1 year ago.

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.

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

Diagnostic light #1 flashing and #2 on solid?

Customer: replied 1 year ago.
that's correct.
Expert:  Tim H. 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.

Customer: 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?
Expert:  Tim H. replied 1 year ago.

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

Customer: replied 1 year ago.
No it's not running now
Expert:  Tim H. replied 1 year ago.

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

Customer: 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.
Expert:  Tim H. replied 1 year ago.

Unplugging it?

Customer: 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.
Expert:  Tim H. replied 1 year ago.

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

Customer: replied 1 year ago.
Ours does. I can send a picture if that helps.
Expert:  Tim H. replied 1 year ago.

Well, lets plug back in and see what happens.

Customer: replied 1 year ago.
Hello?
Expert:  Tim H. replied 1 year ago.

Well, lets plug back in and see what happens.

Customer: replied 1 year ago.
Done that and now we have no lights and nothing is working.
Expert:  Tim H. 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.

Expert:  Tim H. replied 1 year ago.

If nothing, check breaker. Maybe it tripped.

Customer: replied 1 year ago.
Where is the power switch?
Expert:  Tim H. replied 1 year ago.

Should be right by the unit looks like a light switch

Expert:  Tim H. replied 1 year ago.

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

Expert:  Tim H. replied 1 year ago.

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

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

Did you check circuit breaker?

Customer: replied 1 year ago.
it's on.
Expert:  Tim H. replied 1 year ago.

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

Expert:  Tim H. replied 1 year ago.

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

Customer: replied 1 year ago.
Plug has power checking fuse now
Customer: replied 1 year ago.
Fuse is good
Expert:  Tim H. replied 1 year ago.

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

Customer: replied 1 year ago.
No LEDs are not flashing.
Expert:  Tim H. 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.

Expert:  Tim H. replied 1 year ago.

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

Customer: replied 1 year ago.
Getting meter now
Customer: replied 1 year ago.
Still working on it
Customer: replied 1 year ago.
No not 24 volts getting 0
Expert:  Tim H. replied 1 year ago.

Did you push in blower door switch while taking reading?

Customer: replied 1 year ago.
Ok getting 5.2 volts when push in switch. Also getting buzzing noise when push in switch.
Expert:  Tim H. replied 1 year ago.

Sounds like a possible bad blower motor. 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:

Customer: replied 1 year ago.
Ours doesn't look like that ours only has three burners
Customer: replied 1 year ago.
Pic attached. Where is the limit switch?
Expert:  Tim H. 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.

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

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

Customer: replied 1 year ago.
Do you have a part number?
Expert:  Tim H. replied 1 year ago.

see here

Expert:  Tim H. replied 1 year ago.

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

Customer: replied 1 year ago.
We found it.
Customer: replied 1 year ago.
It's done power back on. What should happen?
Expert:  Tim H. 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:

Customer: replied 1 year ago.
Ok did that. Now what?
Expert:  Tim H. replied 1 year ago.

See if you now have 24 volts across C to R

Customer: replied 1 year ago.
No do not still 5.2
Expert:  Tim H. replied 1 year ago.

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

Expert:  Tim H. replied 1 year ago.

Transformer may look similar to this.

Expert:  Tim H. replied 1 year ago.

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

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

No, just an example.

Expert:  Tim H. 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.

Customer: replied 1 year ago.
Ok give us a minute
Customer: replied 1 year ago.
Do we keep the limit switch wire disconnected?
Expert:  Tim H. replied 1 year ago.

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

Customer: replied 1 year ago.
125v
Expert:  Tim H. 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.

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

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

Customer: replied 1 year ago.
Anyway to get in touch with you again?
Customer: replied 1 year ago.
Do we get s case number?
Expert:  Tim H. replied 1 year ago.

Just bookmark the page.

Expert:  Tim H. 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.

Customer: 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!
Expert:  Tim H. replied 1 year ago.

Thanks for the update.

Customer: 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: replied 1 year ago.
Still no lights. What's next?
Expert:  Tim H. 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

Customer: replied 1 year ago.
Refer to picture white common black 120v yellow common blue 26v. Across C to R is 5v.
Expert:  Tim H. 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.

Customer: 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: replied 1 year ago.
What do you think?
Customer: replied 1 year ago.
The request for phone call was a mistake my phone was freezing.
Expert:  Tim H. 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.

Customer: replied 1 year ago.
Does this help?
Expert:  Tim H. replied 1 year ago.

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

Customer: 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!!
Expert:  Tim H. 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.

Expert:  Tim H. 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.