Have HVAC Questions? Ask an HVAC Expert for Answers
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.
Diagnostic light #1 flashing and #2 on solid?
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.
Could also be the pri***** *****mit. Is the fan running continuously?
Check your blower. Maybe the blower motor is bad causing it to trip out on the limit.
Hmmm, unusual for a furnace to have a plug in cord.
Well, lets plug back in and see what happens.
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.
If nothing, check breaker. Maybe it tripped.
Should be right by the unit looks like a light switch
You may not have a power switch if you have this plug in cord.
Very unusual for a furnace to have a plug in cord, by the way.
Did you check circuit breaker?
Check the plug in that you are plugging it in at. Make sure it has power.
If the plug in has power, next check the fuse on the control board. See if it's blown.
If fuse seems OK, then the LED's should be slow flashing.
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.
Make sure blower door switch is pushed in when you do this.
Did you push in blower door switch while taking reading?
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:
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.
Doesn't matter how many burners. The limit will look the same.
It is a brown flat piece of plastic with two wires attached. About the size of a playing card.
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:
See if you now have 24 volts across C to R
Not making sense. You must have a burned out transformer, then.
Transformer may look similar to this.
You do have voltmeter set to volts AC, not DC correct?
No, just an example.
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.
Previously you taped the metal ends of the two limit wires together. Leave this way for now.
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.
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
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.
Just bookmark the page.
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.
Thanks for the update.
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
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.
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.
I show part # ***** Found one here. But you may want to check around for better prices.
It doesn't have to be any one thing. Boards go bad all the time. Remember, this furnace is not exactly new.