I have a Day & Night gas furnace - Model Number 376CAV036075 - that was installed 32 years ago (I know, I should replace it but, unfortunately, I'm very poor). When the furnace quit working (the inducer motor would run but would 'time-out' after 90 seconds without the burners igniting), my research showed that among the list of possible causes was the flame sensor and since it was the least expensive component on the list, I tried replacing that. It didn't solve the problem.

I took the cover off the furnace (no easy trick as the furnace is installed under the crawl space in my home - very little room and I'm 'large') and the red LED on the printed circuit board was flashing a 1-4 cadence, which means the circuit was locked out for 3 hours. I reset the furnace, the LED came on steady and I ran a jumper between the test terminal and the 24VDC terminal. The LED went began flashing fast. Does anyone know what this means? Or what the problem might be? I'd be grateful for any help.

Please stay safe and healthy.

 

Welcome to the forums.

Please read the "read first for furnace repairs" sticky at the top of the forum.

 

So, I read the ‘sticky’ about gas furnaces but it didn’t help me read the error code. Does anyone have or know where I can find out how to read the LED when in the test mode? Apparently on my unit, you can place it in a test mode by running a jumper wire from a specific terminal to 24 volts. Thank you.

 

The codes are listed on the back of the blower door.

 

Pete-
Thank you for the reply, however, the codes for the LED that are on a label inside the door are for when the unit is NOT in the test mode. I’d like to find how to read the codes when the unit is in the test mode but I can’t find it anywhere.

 

That board has a test routine where it will test components.
I'm not aware of it displaying any fault codes during this routine.

The original control board would have been a CESO110057-02.
There were other similar boards used.
The ICM-281was the universal replacement board for it.
The pdf file describes the limited tests it can run.
ICM-281 pdf manual

 

What trouble code are you getting?
3 fast and one slow flash?

Remove the pressure switch tubing from the furnace and ream out the tubing nipple with a straightened paper clip.