HVAC

Ask a HVAC Question, Get an Answer ASAP!

Have your own HVAC question?

HVAC Technicians are Online Now

characters left:

Not a HVAC Question?

Question

I own a six year old Trane XR-80 furnance. Last week I realized when I awoke one morning and the house was COLD that the furnace was not working properly. I see that the CNT-3798 control board has an LED on it and it is flashing. Being an EE myself, I must assume that the fact it is flashing a three dot sequence has a diagnostic meaning. Since none of the info I was originally left with tells me what that means maybe one of you folks out there could enlighten me. I have no problem working on the unit myself but I need some specifics.

Submitted: 344 days and 14 hours ago.

Category: HVAC

Value: $15

Status: CLOSED

Posted by coolman1973 344 days and 13 hours ago.

Answer

Hi, did u look at all the stickers in the furnace and on the inside of the blower door?

344 days and 13 hours ago.

Reply

Yes, there is nothing to explain the LED blink sequence. I was hopiong that someone here would ahve had the info and could tell me
what the LED is trying to tell me.

Posted by coolman1973 344 days and 13 hours ago.

Answer

why dont tell me what happens when to start it? sequence of operation

344 days and 13 hours ago.

Reply

When it first starts, a small motor starts, then you normally can hear the burners kick on, then the main blower starts. What happens now is the small blower starts, but you never hear the burner kick on. It retries several times before shutting down. Then the sequence starts again. It does occasionally work, but that seems to happen after it thoroughly cools down. I must assume it is some sort of thermal problem, as once it gets hot it refuses to operate but I'm just not sure.
What do you think, is a new control board in order?

Posted by coolman1973 344 days and 13 hours ago.

Answer

what type of ignition system does it have, spark or hot surface, and after the inducer motor starts do u hear or see this ignition system try to work

344 days and 12 hours ago.

Reply

It is an electronic, pilotless, ignition. It does sound like the ignition trys to start but does not. As I said it seems to be a temperature related failure. I'm wondering if their could be a heat sensitive part in the circuit board.

Posted by coolman1973 344 days and 12 hours ago.

Answer

when u hear that sparker u shoul then hear the gas valve click in, if not retry and put a meter on the gas valve terminals and see if u have 24 volts when its trying to start. if u dont then u have a control board problem, if u do then ur gas valve is failing. those blinking lights or most likely a ignition lockout code

344 days and 12 hours ago.

Reply

Thanks for your help. I'll give that a try.

Accepted Answer

sure no problem

Accepts:
Expert:	coolman1973
Pos. Feedback:	95.9 %
Answered:	12/13/2008

Hvac tech and Mechanic

15 yrs field exp/5yrs supervisingexp/ Nate and Epa cert.

Disclaimer: Information in questions, answers, and other posts on this site ("Posts") comes from individual users, not JustAnswer; JustAnswer is not responsible for Posts. Posts are for general information, are not intended to substitute for informed professional advice (medical, legal, veterinary, financial, etc.), or to establish a professional-client relationship. The site and services are provided "as is" with no warranty or representations by JustAnswer regarding the qualifications of Experts. To see what credentials have been verified by a third-party service, please click on the "Verified" symbol in some Experts' profiles. JustAnswer is not intended or designed for EMERGENCY questions which should be directed immediately by telephone or in-person to qualified professionals.

HVAC

Have your own HVAC question?

Related Hvac Topics:

Question

Answer

Hi, did u look at all the stickers in the furnace and on the inside of the blower door?

Reply

Yes, there is nothing to explain the LED blink sequence. I was hopiong that someone here would ahve had the info and could tell me what the LED is trying to tell me.

Answer

why dont tell me what happens when to start it? sequence of operation

Reply

Answer

what type of ignition system does it have, spark or hot surface, and after the inducer motor starts do u hear or see this ignition system try to work

Reply

It is an electronic, pilotless, ignition. It does sound like the ignition trys to start but does not. As I said it seems to be a temperature related failure. I'm wondering if their could be a heat sensitive part in the circuit board.

Answer

Reply

Thanks for your help. I'll give that a try.

Accepted Answer

sure no problem

Related HVAC Questions

Yes, there is nothing to explain the LED blink sequence. I was hopiong that someone here would ahve had the info and could tell me
what the LED is trying to tell me.