I have been having very similar problems to what I have been reading about Bryant furnaces and the 3amp fuse blown. I have lived in my house for almost 5 years and the house is 11 years old. I have replaced the 3amp fuse probably a dozen times and I have recently replaced the t-stat. The furnace has always worked for an extended period before the fuse blows again. Just yesterday I replaced the blown fuse only to have it blow twice within minutes of turning on. My furnace guy came by this time determined to find the cause. He checked all of the wires leading into the t-stat and found continuity when there should not have been. He traced the wires from the circuit board as they come out of the unit and head up the side towards the t-stat. Just about two feet up the side of the sheet metal the installer put an installation screw accidentally just enough into the t-stat wires that is was causing an intermittent short that has progressively gotten worse as the furnace vibrates causing the pointed end of the screw to work its way further into the t-stat wires. We spliced the t-stat wires to remove the damaged section. My furnace is working properly now and I believe this will no longer be an issue. Hope this helps someone else.

I have this code but have no idea where to find the secondary voltage fuse. My Bryant air conditioner was functioning fine until I changed the batteries in the thermostat. At that time the air quit working. At first I could jump run the blower in the on position but not in the auto position and the outside unit wouldn't come on at all.
Then things got worse. Now nothing will work. I have a 2 rapid/4 slow code and would like to replace this fuse if I know where to look for it.
Please help!
Thank you... Tim

I know this is old (3 years old) but wanted to see how it went when the tech replaced the transformer in your Bryant. I am having the same issue and am thinking I need to replace my transformer.

I know this is old (3 years old) but wanted to see how it went when the tech replaced the transformer in your Bryant. I am having the same issue and am thinking I need to replace my transformer.

What is looks like is I have a short somewhere in the low voltage circuitry that is blowing my 3A fuse on my control board.

HERE IS THE ACTIONS THAT OCCUR
1. Fan turns on
2. About 8 seconds later the pilot lights
3. Burns for 60 seconds
4. Then fuse blows, and blower turns on blowing cold air through out the 5. House (because there is no more flame)

Unfortunately I cannot find the short. Any idea's

What burnes for 60 s?

Pilot or Burner?

It would seem it could be the main gas valve.

The pilot lights, then I hear clicking over and over again like a grill lighting, but the burners never turn on. At 60 seconds the blower starts at the same time the 3A fuse blows.

I have been debating if the flame sensor is dirty, or bad, or if the gas valve is not working. I have a new control board and wiring harness. Verified the voltage before and after the transformer and its 110 in and 24 our to SEC1 and SEC2.

Not sure how to test to see if the flame sensor is working(I can't even find it on the old Bryant Plus 90) But thought is either the flame sensor is not telling the control board there is a pilot, or the control board knows there is a pilot and is telling the gas valve to open, but the gas valve is not opening.

I'm confused somewhat.

Verify at least that the fan works in FAN mode and that it works in the AC mode. I suspect it will.

In Heat mode, the furnace controls the fan. In AC mode, the thermostat controls the fan usually,

It's also possible that the main gas valve is bad and don't know if you can disconnect and see if the fuse doesn't blow.

Unfortunately, I'm not sure what kind of system we are dealing with, In some cases, the "thermocouple" gets heated and it turns on the gas valve.

i.e. A purely mechanical failsafe. ON, then thermocouple gets heated and the gas valve turns on due to the expansion of the junk inside the tube.

So,not sure if you have an older system or an electronic flame detector. That uses flame rectification and you have to be able to measure a very small current.

Easy to tell, if the flame sensor has wires and goes to the control board it's electronic and it can be cleaned with emory paper.

A mechanical flame sensor, "thermocouple" will generally be a small copper tube.

Pictures, wiring diagram could help.

The 24 VAC fuse blowing when it does, I would think indicates a probem in the 24 VAC system and I "don't think" it's the thermostat or wiring to/from the stat.

One other possibility is the 24 VAC phasing if the sensor is electronic. If you accidentally reversed the wires to the 24 VAC secondary or Primary, the flame sensor may not work.

The fan works in AC mode, and on just fan mode. The fan also works in heat mode.

"It's also possible that the main gas valve is bad and don't know if you can disconnect and see if the fuse doesn't blow."
So from this, if I get what you are saying, I should be able to disconnect the wires that go from the control board to the gas valve, and if after 60 seconds (when the blower turns on and the burners should be lit) the fuse does not blow, then it would mean the short is in the gas valve?

The unit is an old Bryant plus 90, upflow furnace. About 15-20 years old. But I don't see the flame sensor, but the burners and pilot are in a burner box which is hard to get to without tearing the burner box apart.

Tonight I will post some pictures of the burner box, gas valve, control board and the wiring diagram from the Control board and inside of the side panel.

Here is a link for the YouTube video that I recorded with the full cycle and pictures of all the components
Full cycle until furnace 3a fuse blows - YouTube

Do you have an actual model number from the nameplate?

I think the first part of the model points to the carrier base 398AAW0 and the second part 360600 has something to do with Bryants naming.



The full model on the sticker is 398AAW0360600

The product on the sticker is 398AAW0360600AEBA


So my guess that Bryant added 360600 and AEBA probable is some sort of a version information