issue with Bryant three wire pilot

zepfan

I was posting to see if anyone had a had a similar issue with a carrier/ bryant furnace that was very popular in the early 90's. The furnace in question is a Bryant model# 394gaz048125. The furnace just had the three wire pilot, and the gas valve replaced. The problem is that it is not establishing pilot most of the time. When it does it has no problem with the pilot switching over, and energizing the main valve and lighting the burners. The pilot will spark, but will not light. It is like the gas is just going around the pilot burner, and not igniting. I even tried an orifice in the pilot burner that you could push a 1/16" drill bit through, and still no luck. You can actually light the furnace manually with a match, and then everything will work like it should for one thermostat cycle. But that is something that I tried just to see if everything worked, and obviously not something that I want the customer to do. I don 't know what else to do other then to change the electrode on the side of the pilot burner. The furnace is old and probably should be replaced, but that does not excuse it from not lighting now. Any suggestions would be much appreciated. thanks to all.

Tim McElwain

Let me see if I can dig the manual for that one out of my very extensive library on older units. I will get back to you asap.

zepfan

Thank you Tim. I actually called Carrier today, and they were of little assistance. They just said that the air/ fuel mixture is off if it will not light automatically, but does with a match. I went back to the job, and replaced the electrode, still no luck. I had another pilot burner on my truck, and I bent the pilot hood down to the point that the spark was in direct line of the gas, still no luck. I appreciate you looking for the manual. I even tried another high voltage cable, and another ignition module that I had as a spare on my truck, with no luck.There is no logical explanation as to why this furnace will not light.

HVACNUT

Its probably the gas valve itself if you replaced the pilot burner. Pilot tube and orifice are clear?
Haven't seen a WR pilot burner in about 20 years. And I'm a happier man for it.

unclejohn

You may have too much gas going through the pilot. Take picture of the pilot flame after you lite it with a match. It should not be 3" above the pilot like some I have seen. You can still get that pilot in fact I have one on my truck.

newagedawn

is it wired right?, check the schematic, that should plug in?

zepfan

yes it is wired right, the plug will only fit one way. The nc contacts energize the spark box. After pilot is established the pilot heats up to the point where the nc contacts open de energizing the spark box, and the no contacts on the pilot close energizing the main gas valve. All that works when the pilot is manually lit with a match. It would not work when manually lit, if it was wired wrong.

JUGHNE

Are these replacement parts still around?
I just came across a boiler with what appears to be this pilot/gas valve system. It is working well, but previous flame roll out has started to melt the bottom of the ignition transformer.
It is lighting OK now......very slow sequence of ignition when you wait for it.

Tim McElwain

I have a manual on the 398 system but could not find the manual for the 394 which I know I have somewhere in my library. My problem is that after selling my house and moving my office (it was a full basement) to an 9 x 12 room I can't fit everything in the office so a lot of stuff was moved to the training center and is still in the boxes. I will keep looking. In the meantime some pictures of the controls would help me as I am pretty good at looking at something an figuring it out with what is left of my brain cells.

MikeJ

The famous 3 wire pilot, started out on these when they first came out. I don't ever ever remember one not lighting, after replacing it. So maybe it is the gas valve itself, like said above too much pressure not enough ??

I do know once the wholesale house runs out of their stock, you will not be able to get them anymore. I just checked my carrier site and if the price they have is right its about 4 times higher then last year. If i run across one plan on telling them there not available need a furnace. I can not justify charging that much for pilot

It could always be wire like standing pilot, that be a lot of reliability you be taking on,

https://www.screencast.com/t/ka54fbFq

JUGHNE

I am working on a boiler that has that system.
The flame rolled out one time and started to melt the bottom of the ignition transformer.
The roll out issue has been corrected. However I wonder about the reliability and replacement parts availability for this boiler.

I was considering a standing pilot set up if there is a good setup for mounting the thermocouple?

When I called for a replacement for an old mercury bulb pilot sensor gas valve, parts house said that standing pilot valve was the approved replacement. The thermocouple fit in where the bulb was previously.

Any such luck with the 3 wire pilot system?

MikeJ

Use to carry this on the truck Honeywell Y8610U4001, problem you still need a pilot assembly that it will work on.
https://www.screencast.com/t/QcysWtOcjbD

unclejohn

Try the igniter, should be a nice blue spark. Not rapid just tick...tick...tick. but nice and blue.

JUGHNE

The boiler is lighting just fine now.
I am just trying to be proactive and consider options if the system fails in the future.

He is thinking about replacing boiler.
Between the 3 wire system and somewhat of a questionable LWCO, I think about the advice of repair or replace boiler.

If I posted pictures everyone would say that it will never work, needs complete re-piping etc.

unclejohn

If it works don't fix it.