I have a comfort maker gas heater model number FBF050B12A2.

When I turn on the heat, I see pilot coming on for 1 second and then going off and then try again after 3 seconds. The furnace burner never turn on.

Anyone has any idea what could be the problem.

I also have a short video that shows this behavior.

The draft motor is running. And the fan turns on when I just turn on the fan without heat.

 

Please help

 

Welcome to the forums.

You'd need to post your video in a place like you tube and link it here.

More than likely the pilot assembly will be need to be taken out and cleaned.
There will be a pilot orifice as well as the spark rod that needs to be cleaned.

Have you had this furnace professionally serviced ?
It should be done every few years.

ICP manual - pdf
Service manual - downloadable

 

Here is the link.... video

I will take it out and clean it or just replace it.

I do have a question. The thermocouple has only one wire. I thought a thermocouple should have two leads.

The lead hat is coming out of the pilot shows open with furnace case (ground).

1. All three other temperature protection solenoids show continuity
2. The exhaust motor solenoid was open when not running but showed continuity when running

 

There is no thermocouple there. A thermocouple is only used to keep a standing pilot light lit.

That rod does double duty. It is the spark rod and the spark arcs to ground during ignition.
Once the pilot is lit.... it becomes the flame sense rod. The pilot flame needs to engulf that rod and connect it to ground by the flame. The flame actually creates the circuit. A dirty rod can also insulate it and it won't operate as a flame sense rod correctly.

It needs to be cleaned with a green Scotchbrite pad.

 

I will take out the pilot assembly and clean the rod. Hope fully that will fix the problem.

Is there a way to clean that without taking out the pilot assembly.?

 

I don't think there is a clear shot to it when it's mounted in place.

 

I removed the two screws holding it in place and cleaned the electrode (flame sensor) with a light emery paper and a scotch Brite pad.

That did not fix the problem.

Still the same behavior. I wish there was a way to short the sensor temporarily to see if the main burner fires up.

Without that, should I replace the pilot assembly or something else.

What do you suggest?

​​​​​​

 

Look inside furnace, locate the ignition module and post the model number off it.
It will look similar to this..... Integrated ignition module

If it's a generic S8610Uxxxx ...... this could be helpful..... S8610U general module - pdf

 

I will go up tomorrow again and see the ignition module. It is shown in the technical support manual circuit diagram but is not listed as a replacement item.

How can I check if it is the pilot assembly or the ignitor module that is defective? Is there a simple test?

Do you think the gas control switch is very reliable and should be checked the last?

Thanks for helping me. Even if I have not been able to fix the furnace YET, I am learning a lot.




Also

 

Thank you. I read your ignition module description. It shows how to tell if ignition module is performing well.

Let's see if I can see any error code in the LED. It must be down when the furnace is running and I need to be very careful.

 

I left you the link for what is listed as the current replacement ignition module.
They've gone thru many revisions.
The newer versions have points to test flame sensor current.
I'm not sure what version you have and how to test.
You could take a picture of it and post it.

There is no indication the main gas valve has a problem and since the pilot is actually lighting... the pilot part of the valve appears ok. The pilot is lighting.... it's not staying lit because the module isn't sensing the flame. That could be a defective module or bad burner ground or not a full and robust pilot flame.

The flame itself creates the bridge between the spark/sense rod and ground.
Any problem with the ground path between the pilot assembly and the module can cause a problem.
Double check any visible screws for tightness on the burner and the ignition board.

Measuring the flame sense current is the only way of knowing the exact problem.

 

First, thank you.

The ignition module in my furnace is Honeywell S8600M.

I have found a user manual and will follow it to TRY TO troubleshoot it.

I understand that spark, MV and PV are very high voltage and will be careful not to go close to it.

I will read in the manual if there is an easy way to measure the current. My a current meter only goes to mA and can not measure micro amp.

 

The ua scale is a lower scale than ma.
Try using the ma scale and see if you can get a usable measurement.

1 ua = 0.001 ma

Fig. 13 shows the meter connection on an "M" module.
Does yours have the LED ?

 

I got the HVAC Technician to come and look at it. He did not want to troubleshoot the problem. Said that was a very old units and parts are not available. So best to get a new unit installed

He wanted to give me a quote for installing a new unit.

So looks like I will have to troubleshoot it myself with all your help.

Thanks in advance.

 

Unfortunately my ignition module (Honeywell S8600M) does not have any LEF. But I do have a detailed troubleshooting guide

 

I carry a spare module with me when I service.
I've soldered flame sense test wires right to the board.

 

What is a flame sense test wire?

 

Ok. So I have down some troubleshooting.

I disconnected MV. And then turned the heat on. The spark is working, the flame comes on, but very small and does not stay lit. The flame came on, very weak, and then died. Shouldn't it stay lit?

I did not clean the gas nozzle or adjust the gas valve.

Don't you think the pilot flame should stay on even if the main burner does not come one. Or does it turn off if the flame sensor shows no current? Does the flame sensor only controls the main burner gas valve?

Should I check PV voltage? Should it stay on 24V while pilot flame is on?



Do you not think that Pilot nozzle could be clogged with dust or something? And that is why the pilot is weak and does not stay lit.

 

Should the pilot stay lit even though the flame sensor is not giving any current?

Should PV voltage be constant 24V or if there is no flame, it turns off?

 

The ignition module creates a spark and sends 24v to pilot valve at same time.
As soon as the rod detects a flame it shuts off the spark.
If the flame is too small it shuts off the pilot valve and restarts. Over and over.
It needs to let the pilot stabilize before the main burner opens.
If you're only getting a small pilot flame... that's your problem. It needs to be fairly robust.
You need to check the pilot orifice.

14 is the open gas line. 12 looks like the orifice. The gas comes thru the gas line under fairly high pressure. It's restricted by the orifice which has a hole in about the size of a human hair... a tad bigger. It's shot up the pilot assembly where it mixes with air and become the flame.

 

I thought I could find a video for you. This is a standing pilot.... not intermittent like yours. Same pilot part. Here's Gray. Good videos. At 3:20 he shows the orifice hole but not cleaning it. You can use something small to clean it. Straight pin, wire brush bristle, etc. You can blow thru the pilot gas line after cleaning the orifice to make sure it's clear......... pilot video

 

I disconnected MV.

Turn the heat on and measured voltage between PV and PV/MV.

It has no DC voltage.
There was a 24V AC voltage for a second while spark was on. Once the spark goes out (about a second) the voltage also goes to zero and the flame goes out as well..

4 seconds later the same cycle repeats.

Does this show that module is defective and should be changed.

If yes, what module should I buy?

 

So looks like, I get a robust spark and get 24V AC on PV. So the valve opens and pilot gas flows. But the flame is weak (but not sure. Because it stays on only for a second) So there is not enough current between the pilot and flame sensor. So the ignition module shuts off PV and pilot gas stops flowing. Does it make sense?

Ok. So a few questions
Is this observation shows that the flame rod not working?

Is this observation shows that the flame nozzle is clogged?

The First or the second or both? Shouldn't the flame should be on for a few seconds before checking if the flame sensor is showing current. Why to shut off after 1 second? That is not enough time to stabilize the flame and show current between flame sensor and pilot. Should the ignition keep the PV valve on for longer than 2 second even if there is no flame?

Does it also show that the ignition module is working?

I hope by 24v you meant 24v ac.

 

There is no DC used.... only AC.
You said you had a small flame. The flame MUST be robust. It must blast over the igniter and hit ground.
The flame is conductive and is what keeps the pilot valve open.
If the flame isn't large enough the system thinks it's not lit and turns the gas off and retries the ignition sequence.

 

Got it thanks.

Since the pilot is on only for a second, it is hard to tell if the flame is strong or weak.

LLooks like you are feeling that the problem is in pilot assembly

There are two available.

One genuine OEM from ConfirtMaker for $199

Or generic made by Honeywell for $60.

Which one should I buy?

International Comfort Pro Burner Pilot/IGN N&L https://a.co/d/eEECU1k for$199

Q3451B1178 Q3451B 1178 Honeywell Upgraded Universal Replacement Furnace Pilot Burner Ignitor Igniter https://a.co/d/9Vvn0fe for $64

Which one would you recommend?

 

I don't know why the OEM is so expensive.
It looks like the Honeywell unit will work fine.

Did you try cleaning the pilot ?
I've never changed a pilot assembly before although many members here have.

 

Thank you once again.

I was looking for a thin wire to clean the nozzle. All I found was a safety pin. Not sure how big the nozzle hole is. But I will try

I also have a air duster can. If the pin does not work, I will disconnect the gas line and use the air duster to blow out any dust that might be there.

If that does not work then change the pilot assembly. If that does not work, I will change the ignition module. Or maybe I will change the ignition module first and then the pilot assembly.

Does that make sense?

Above all, I learnt a lot during this project. .

 

Makes sense. Sometimes a piece of copper wire from cat5 cable.

 

I have a question, just to understand things better

Why do you not think that the ignition module is defective. Here are some of my observations
1. I have cleaned the flame sensor rod2. The PV voltage (24v) only lasts about a second after the pilot flame comes on. I measured it using a voltmeter. Shouldn't it stay on for 2 to 4 seconds to make sure that the flame is stable and current can flow to the flame sensor?
3. The flame does come on which means that the spark is working.
4. It is hard to tell how strong is the flame. Since it stays on only for a second.
5. It is true that I have not cleaned the pilot gas nozzle which I will do next.

Let me know your thoughts . Thank you.

 

The pilot should come on instantly with a little roar. Should sound like a little blow torch
Since the pilot is only on during a call for heat... I like a little stronger flame.
Since the spark is stopping it is seeing the flame but it's not strong enough to sustain operation.

If it didn't sense the flame at all..... it would keep sparking until the 4 second timeout.

 

Opened the pilot flame nozzle. Cleaned the nozzle and put it back.

No change in the flame. Still comes on and then dies within a second.

Next I changes the ignition module to S8610U3009.

With this module, I did not get even a spark. Checked all connections but did not find anything wrong.

The box said something about not connecting to 24 V, not sure what it meant. Please explain.

 

I didn't see your old wiring but you should put your power wire on TH-W not the 24v terminal.
Did you try the new module with a wire on 24v ?
That tells the new module that you have a vent. You don't have a vent.

 

Thanks . Will try again. Maybe third time a charm

 

from page 8..........
*IF INSTALLATION DOES NOT INCLUDE VENT DAMPER WITH PLUG CONNECTION TO MODULE:
1. Leave vent damper plug on S8610U Module in position.
2. Use TH-W terminal.

 

In my old ignitor module, one wire is connected to 24V and one to GND. And no connection to TH-W (OPT).

Here is the photo.

 

I do have a motor at the exhaust that is connected to a vacuum solenoid. This exhaust motor starts ahead of pilot lighting sequence.

 

A motorized damper is located above the furnace in the metal flue line. It is not inside the furnace.
It sounds like you are describing a draft inducer that is bolted to the front of the burner.
This would be a motorized damper.

 

Ok. So I do not have a motorized. Damper and should use TH rather than 24V.

But why was 24V rather than TH (OPT) was connected in my old ignition module S8600M?

Another small question, I do not see any 24 V on the leas that connect to 24v in my old module S8600M even though spark works fine.

Sam

 

When pilot come on for one second, in my furnace with the old ignition modulw, it is like a blue candle and does. Not roar.

Do I need to adjust the pilot valve so that more gas goes to the pilot? H