We recently purchased a home that has Day & Night forced air furnace circa. 1986. Model 305318-201 (396jaw048065). Natural Gas. I believe Payne has the same model number. We live in SF Bay Area.

The main blower always remains on. Thermostat is basic and does not have option of fan to be on AUTO or ON. Moreover, when thermostat is turned on, furnace does not turn on. In other words, regardless of temperature setting on thermostat, blower fan is always on and furnace does not light.

We conducted the following test
1. With temperature on, we established that the igniter does not light pilot light.
2. We do not hear the typical "click" that accompanies igniter starting.
3. Blower goes off only when we physically disconnect power chord to the furnace.
4. Per DIY post elsewhere, we tried to test for stuck power relay. To test, it suggested removing G wire from the circuit board. I did not find G but only GC. When we removed this wire that was coming from the thermostat, there was no change. Blower continued to run.
5. Per DIY post elsewhere, we tried to test transformer. We located two terminals marked SEC 1 and 2. Voltage reading at the terminal was about 27V.
6. Per DIY post elsewhere, it said that blower remains on unless the relay is energized. To test it, we need to measure voltage between R & C. We could not find any terminal labeled R or C. Where should we look?

In addition to this, what else should we test?
Above all, are we testing the right stuff?

 

Four things can cause no heat with continuos blower in your furnace
1-bad transformer (which you ruled out)
2- open fuse link
3- open limit/ rollout switch
4- bad board

 

How do I test fuse link?
How do I test open limit/rollout switch?

 

Hi, I'm having similar problem with my Day and Night furance, model 376BAW036055AABA (from BDP Carrier) that the blower fan is always on when the power is plug in. The pilot does not light and I don't hear any clicking sound. I was wondering if anyone have this problem and had a solution.

Thanks,

 

What happens when you turn the stat switch to off?

 

When I turn off the Thermostat, there is no change the blower fans turns on when the power cord is plug in. I don't hear any clicking sound or anything else other than the fan running. I measure R and C on the PC controller board and have no voltage (checked both DC and AC). Can anyone give me any advice what I should do next to isolate this problem.

I haven't gotten a chance to measure Sec 1 and Sec 2 yet of the transformer. It was located in a area where I can't get to on the board.

Should I check for any open circuit, if so, where should I check. Thanks

Model: 376BAW036055AABA
Company: Day and Night (BDP Carrier)

Attached is picture of controller board

 

No volts on R to C, You will have to check the transformer and also check to see if there is fuse. Usually 3 amps.

 

Look at my post, number 2

 

As mbk3 mentioned as open limit switch will cause this problem. With this line of equipment the blower fan runs until it's told to shut off. It's a very common problem for one of the high heat safeties to open. You need to use an ohmmeter to determine continuity on these safeties. There can be two or three stats. but most likely it's just one that is opened.

 

Hi, PJMax, mbk3 and skaggsje, looks like open fuse link was burned up at multiple places across wire. I also checked it with an Ohm Meter and I got an open circuit. Do you guys recommend me jumpering (bypass with another wire) and give it a try first before I look for a new one. By the way, any advice on where should I look for one of these wires, I don't see a part number anywhere.

By the way, this is for a Carrier BDP, Day and Night furnace, model number 376BAW036055AABA, Natural Gas, Horizontal downward.

Here are some pictures of the burn open fuse links (two of them are burned)

Thanks in advance,

 

Since you mentioned two fuse links I have to suppose they are located around the burner area not up on the limit switch. Since you found them damaged it appears there may have been "flame rollout" and for that I would call a pro to check it out