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timothyr 10-11-2006 07:05 PM

Heil Furnace Burner Problem
I have a Heil DC90 furnace installed in 1999 as a new furnace in a new home. We usually have the blower on during the winter because it helps keep the temperture in the house more balanced. Last winter we did this and the furnace worked fine most of the time, but a few times the pilot would light but the blowers would try to start but go out immediately. The furnace would then just blow cold air until I reset it. The pilot light stayed lit the entire time. I had a service man come out and take a look. He cleaned the ingniter and pilot, but it didn't make a difference. (Note: If the blower is set to auto on the T-stat, the furnace works fine, the problem only occurs when the blower is set to on).
This year I decided to have the service man back to look at it again. I had him replace the igniter. It didn't help. It appears as though the burners are being blown out from the air running through the furnace, like there is an air leak allowing air into the heat exchanger. THe pilot appears to dance around a little if you watch it through little pilot window. The tech said it might be a leak in the seal between the exchanger and the front wall of the furnace. I've read through some of the previous post and didn't find a solution. Anybody else have any ideas? I know I could just leave the furnace on auto, but it worked before and now it doesn't. The service tech is pretty knowledgeable and I have a pretty good understanding of how the furnace works, but this has us both baffled.

JimK 10-14-2006 10:04 AM

I'm having the same problem, but the blower is set to auto. It's happening more and more often. I've had the exhaust fan (blower?) changed and the problem is still there (the fan had a noisy bearing, so it needed to be changed anyway.) Fan starts for 15 seconds, igniter fires and no burn - just see a little flicker through the check window. I'm hoping somebody knows what this is caused by. Haven't found anything online yet.

redline 10-15-2006 07:06 AM


Originally Posted by timothyr (Post 20563)
but a few times the pilot would light but the blowers would try to start but go out immediately. The furnace would then just blow cold air until I reset it. The pilot light stayed lit the entire time. He cleaned the ingniter and pilot, but it didn't make a difference.


The ignitor is the pilot. The ignitor lites the gas as it comes out of the gas valve.

When you say that the pilot light stayed lit - are you saying the ignitor was glowing?

timothyr 10-15-2006 11:16 AM

Sorry for the confusion. The pilot is lit and I believe the ignitor is glowing as well. The main burners aren't lighting. This only happens if the fan is set to the "on" position on the thermostat.

JMarshall 10-17-2006 08:56 PM

I'm having the same experience with my DC90 that was also installed in 1999. It does it in auto and the problem has exsisted for 3 years now. I have replaced the control board and flame sensor with no resolve. I'm trying to get Heil to address this problem but so far they have not been very cooperative.

#CARRIERMAN 10-19-2006 11:52 AM

Hi timothyr

It sounds like you have a smart valve set up on your furnace, I this is so the only way to fix this problem is to replace the gas valve. If it does have the smart valve system, the gas valve has the flame ignition and proving circuit built in. And the answer to your next question,they are very expensive.

Good luck, let me know if I can help.

mdshunk 10-19-2006 04:58 PM

The only thing "smart" about the Smartvalve was the business decision to use them in furnaces. They are a boon to the HVAC service industry, as they are all too common failure items.

Wolffman 10-20-2006 12:25 PM

I have this same issue.
At times the furnace operates properly but many times once it reaches it preset temp and switches off it won't cycle back on. If I do a power cycle on it it functions as designed until the next cycle.

I am not 100% sure but at the end of the A/C season it seemed to be doing the same thing (obviously it was the A/C not cycling not the heating unit). Would this be consistant with your "smart valve" diagnosis or ?

Thanks in advance.

#CARRIERMAN 10-20-2006 12:58 PM

Hi Wolffman

There are many things that cause the problem you are having. Probably the most common for the problem it sounds like you are having is an intermittent limit trip. The major causes of this is either a dirty filter, plugged blower wheel or evaporator coil. The plugged blower wheel and evaporator coil will cause the limits to fail completely if not repaired. This is also a major contributor to early heat exchanger and compressor failure. Unplug your furnace or shut the breaker off to it. Pull the blower compartment door, carefully reach in and feel the vanes of the blower wheel if you pull a bunch of dirt back on your finger. You will need to have the evaporator and blower pulled and cleaned. I am just guessing that this is the problem. If you could give me a little more information I could pinpoint it for you.

Good luck

Wolffman 10-20-2006 01:03 PM

#Carrierman thanks for the info.
I have noticed reduced airflow and a whistling like noise also. I replaced the filter ( yes I have neglected to do that on a reg basis like a dummy ) and it seemed to improve but as near as I can recall it is still noiser than previously and noticeably noiser with the filter in.

Any other info that would help on your end just let me know.
Thanks for the help you have already provided. I am going to check it out tomorrow based on what you have said so far and any further advice.

#CARRIERMAN 10-20-2006 01:17 PM


It's ok, You would be amazed the houses that neglect their equipment. If you have a HVAC company that you like to use, they will need to pump your a/c down and completely remove the evap coil. I personally like to use the foaming condensor coil cleaner to make sure it is spotless. Make sure if they use this method that they thoroughly wash evap out. The condensor cleaner is not intended to be left on the coil. Make sure they completely dismantle the blower assy and wash the wheel good. Make sure they also install a good quality liquid drier and pull a good vacuum on your refrigerant system. If they are a good company, you will be happy with the result.

Good luck

Wolffman 10-20-2006 01:44 PM

I should know better.
Being an automotive technician for 20+ years I am not new to maintaining things and the results when doing so.

Jscho 10-25-2006 10:06 PM

Hello, I am a complete furnace novice, although just had a Heil gas furnace/AC installed this past spring. I have had the same issue with the furnace not "firing up" on a consistent basis. My installer told me the following (please excuse my lay person explanation and I am sure he gave me the "dumbed down" version!)...He said he called tech support and that there is an issue with the burners and the air flow. The recommendation was to replace with a improved burner that addresses the issue. When I asked, he said there is not an actual recall on it. So, he changed my burners and I have had not one problem since. It was very inconsistent before and I would have to reset it with the switch to get it to work. It also did not matter if it was actually off and I turned the heat on or if the thermostat tripped it. So, I cross my fingers that I will no longer have problems since it was a big concern to have a problem so fast!!! I hope this makes some sense for you guys and it is maybe helpful!

#CARRIERMAN 10-25-2006 10:38 PM

Hi jscho

This is not a hard problem to fix, The particular furnace you have should be hot surface ignition. This is a M shaped piece with a porcelin base. What happens to these is depending on the time and day they were built, rather it be 5:00 on friday before the hangover or 8:00 on monday afterwards. Heil has had some problems with ignitor alignment, now your getting ready to become a service tech and not a novice. First locate your ignitor, the M part of the ignitor should be aproximatly 3/8" away from burner. DO NOT TOUCH THE M PART! the oil from your fingers will cause it to hotspot and fail. The second thing you will need to do is make sure that the M part of the ignitor is positioned in front of the fluted part of the burner (this is the little part that looks like a bunch of fingers around the inside of the burner). Remove the metal bracket and ignitor and carefully bend the bracket to achieve the peramiters I gave you. Make sure that when you reposition it that your power is off to the furnace while doing so and that when you are done the M part of the ignitor is not touching any metal. Once you are done, plug your furnace back in and make sure it fires up every time. The reason most technicians tell you they need to call the factory is they have no idea how to fix your problem. Very seldom does any manufacturer allow a piece of equipment to leave the factory in a unoperable state. The repairs are generally minimal.

Good luck, let me know if I can help further.

Jscho 10-26-2006 09:32 PM

thanks Rusty.
Hopefully this is what my installer long as I have consistent heat this winter and my house does not blow up, I am happy! And, so far, so good. After reading your post, I remembered that he said something about ignitor alignment so hopefully he figured it out! Thanks again. J

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