14 replies to this topic

[Nicky]

When calling for heat the electronic ignition is sparking and there is a brief ignition from the pilot tube, but no gas to main burners. It is cycling and after many attempts, nothing. It was midnight and I didnt test voltage to the valve because of time issues and I was very high on a condo roof without my meter because i thought it was going to be a quick reset like they had 5 months ago. Anyway, the ac is working so the transformer is ok. What would be your best bet on the problem? I appreciate any responses.

[Dan Webster]

Most likely the furnace is not getting confirmation of ignition and is continually trying to get that confirmation. Older furnaces use a kanthal spark/sensor. It does 2 jobs. Lights the burner and then the flames running through it confirm ignition back to the brain. Cleaning the tip of that spark/sensor real good will sometimes be an effective way to get the furnace back up and running while you await a new spark sensor.

Newer models use a flame sensor. The sensor gets contamination on it which coats the sensor and throws off the resistance readings back to the control. Cleaning it with sand cloth or dry brillo pad will sometimes get her back up and running until yall can get a new flame sensor installed.

Video:

Edited by applianceman18007260692, 04 March 2011 - 07:41 PM.

[Nicky]

these are the original units from 1991 on this building. do you think this would be the older style kanthal sensor or the newer style sensor? I'm assuming that these sensors sense the small pilot light that is actually igniting momentarily? I may try to go out there tomorrow. thanks for the response.

Edited by Nicky, 04 March 2011 - 07:52 PM.

[ACtechGUY]

If you have a pilot flame that ignites and no main burner firing, then you have one of 3 very possible problems.
# 1 . if you have a separate spark module(separate from the main circuit board), then maybe the spark module is malfunctioning.

# 2 if the spark function is part of the main circuit board , then your problem is the main circuit board.

# 3 Main burner side of gas valve is failed.

All Post 1990 spark ignition systems that I have seen (in my neck of Louisiana ) work in the same way. They spark(sometimes for a long time on older models ) , Pilot flame ignites, then (sometimes after a delay) , main burners ignite.
Spark ignition systems may not have any sort of flame sensor that you can fix or clean( Flame sensing is built into the spark sensing circuit and not a seperate rod on the end of the burners), .......

SO, if you get spark, and then pilot flame and then no main burners, put a meter on the gas valve and look for 24 volts ac when the gas valve should be opening. If you get voltage at that point then the valve is bad . if you never get voltage there it is the spark module or main circuit board( Suspect whatever part that makes the spark).

Good luck ,
And happy Mardi Gras
http://www.nola.com/...otos-and-video/

[Nicky]

This is exactly what is happening. The spark is igniting the pilot only for a few seconds. and then the pilot goes out and it sparks again. Isn't this saying that the spark is still good and functioning and doing its initial job? When the unit worked correctly are you telling me that the pilot comes on and almost immediately the gas valve opens or is this pilot supposed to stay on longer than it is now? I suspected the gas valve to begin with and i knew i would regret not going down to get my meter. I'm almost hoping it has a sensor. Well anyway, thanks for your help. I'll keep you posted.

[ACtechGUY]

Don't confuse the fact that just because the unit is sparking that everything is ok with the spark circuit.
From what you are describing , the spark control is sensing very little or no flame signal from the pilot flame.
And Yes, Once the control senses a stable pilot flame , the main gas valve will be opened(this could be very fast , or it could take 5 to 10 seconds, older models sometimes had long delays till main gas valve opening

there are several things you can check on the flame sensing circuit .
Spark systems sense flame via chasis ground. ANY CORROSION will mess up the flame sensing circuit.
Make sure all ground connections to the control are good . clean all connections to board .. Clean any ground wires to burners. Pull pilot assembly and clean all metal surfaces that the pilot flame contacts(there will be metal rods or bars that the flame inpinges upon) . The flame contacting these metal peices is how the flame signal gets to ground and back to the control.
Blow out pilot tube with compressed air or something similar to clear out any blockages that may be reducing pilot flame size .

Still have the same problem after cleaning all this stuff????????????????? REPLACE whatever device generates the spark.

Edited by ACtechGUY, 05 March 2011 - 09:51 AM.

[Nicky]

ok thanks. tells me a lot. After checking voltage to the valve I will do all of this if necessary. I stumbled on this post about major failure on 15 of these type of units with the heat exchanger. The rooftop units begin with RRGG like mine. There are 4 units like this on these condos. I will be sure to look for cracks and check for monoxide in all the condo units since i'm sure its never been done. here is the link. thanks again.
http://hvac-talk.com...ad.php?t=477672

[Nicky]

got very brief voltage to the valve every time sparking occured. sparking stopped when pilot briefly came on and then begins to spark again. I removed and cleaned ignitor and checked all connections. Is ignitor also a flame sensor? I ended up removing the honeywell ignitor module for replacement. Hopeful this is the problem.

[ACtechGUY]

The honeywell spark module senses current to ground that proves a flame is present. It depends on the vintage spark module , but most of the time it is just sort of like magic. the module can sense a flame signal from the pilot burner to ground .


This is the spark module you want to get http://www.forwardth...ell/63_9411.pdf
once installed , It will tell you if you have another problem, like bad ground , shorted anything, ect. It is a awesome product.

It is never a bad idea to check a heat exchanger for cracks and rust. The best way to do this is to take the top off the unit.

[Nicky]

ok, i'll pick one up. i tried to post a pic from my phone but it said it was too big. I did read many times on this spark control unit about having to switch the 24 volt line from the 24 v terminal to the th-w terminal instead of where designated to go to get this to work. Someone else posted it was an exact wire switch and it worked perfectly without having to modify any connections. Thanks for the replies

Edited by Nicky, 06 March 2011 - 11:03 PM.

[ACtechGUY]

Holy crap, wiring the new spark module can be a real mind bender due to crappy instructions from honeywell. I have done about 4 of them so far. Two on OLDish boilers(real head scratchers) , two on 25 plus year old furnaces( kinda hard too) . Real easy on an exact replacement situation, but it replaces just about any spark module ever made and as such many older modules use VERY different designations for the same terminals on the new module. But if you can figure it out, they do work great!!!

[Nicky]

Well this unit looks pretty straight forward to be identical as far as markings on terminals. If I get nothing I guess I will have to connect the 24 v to the th-w terminal. Is it a good idea to install a new sparker unit and wire, along with this new spark control module, or is it a high probability that they are ok? I will see if I can pick one up tomorrow at my supply.

[ACtechGUY]

I have had bad luck finding new spark wires.....

But you said it yourself , it was sparking and igniting... so why get a new spark cable??

Just read the instructions that come with the module. Look for the newest version that comes in a pretty black box with a photo of the module on it. that version comes with a trouble code sticker, connectors, and better instructions on what terminals go where.

[Nicky]

Will do. I will post when I'm done. thanks for the help.

[Nicky]

Got the new module in. I went to test and I had the same fate that many of the posters online described. I had no power or activity when calling for heat except for the exhaust fan. I ended up moving the 24 v wire from the 24 v terminal on the module and connecting it to the th-w terminal. I fired it up and everything works great. Thanks for the help AC tech guy and appliance man. The tips and knowledge you passed on will go to future use.

Edited by Nicky, 08 March 2011 - 12:25 AM.