DGAT intermittently lock-outs
Posted: Tue Feb 20, 2007 12:46 am
I have a 10 to 12 year old Coleman-Evcon furnace (DGAT070BDC) and just in the last month or so it started locking out. This is my week end lake place and I came into into this problem my last time down. The house was cold and the T-stat was calling for heat but only the purge pump was running. Reset the T-stat and it seemed to do fine running all night and getting up to temperature. But I caught it in action the following evening. I noticed the purge pump running but the burner not coming on and it locked out several tries in a row. First, the purge pump would come on and run for a bit as usual followed by the ignitor stick firing up and glowing red, then the gas valve opens and the burner ignites for 5 - 10 seconds only to go out. After 3 missed tries on the burner it just stays there locked out until turning the T-stat off and back on. I was there for 3 days and it ran normally most of the week end but it locked out 5 or 6 times. Had tech out on third day and he found 2 gas leaks (I had smelled gas when I first opened the house) - one on a plug on the side of the gas valve and one in the low pressure regulator which he replaced. He said the intermittent ignition problem had to be due to a bad ignition control module and then proceeded to tell me my heat exchanger was bad and I needed a new furnace.
I know a bad heat exchanger is a far more serious problem than the lock-out but I want to state up front I believe this tech was trying to rail road me in to a quick purchase. I talked to some DIY friends and they reminded me that the surest way to know if an exchanger is bad is if when the blower comes on the burner flame dances around. I am pretty certain this is not the case and when I head back down later this week I plan to double-check this so my concern is back on the ignition problem. I picked up a new ICM and after reading several posts on this site I have a feeling the ICM is not the prime suspect although it will be easy to replace. My first question is how likely is a leak in the low pressure regulator a possible cause in an intermittent problem like this? It could be the tech already fixed my problem but I left shortly after he did and didn't get a good feel if the lock-outs had stopped.
What other things should I check when I am down later this week? I wondered about cleaning / or testing the flame sensor but when I mentioned this to the tech he said that if it were the flame sensor the problem wouldn't be intermittent.
Thanks in advance for any help and kudos to a great site!
kc
I know a bad heat exchanger is a far more serious problem than the lock-out but I want to state up front I believe this tech was trying to rail road me in to a quick purchase. I talked to some DIY friends and they reminded me that the surest way to know if an exchanger is bad is if when the blower comes on the burner flame dances around. I am pretty certain this is not the case and when I head back down later this week I plan to double-check this so my concern is back on the ignition problem. I picked up a new ICM and after reading several posts on this site I have a feeling the ICM is not the prime suspect although it will be easy to replace. My first question is how likely is a leak in the low pressure regulator a possible cause in an intermittent problem like this? It could be the tech already fixed my problem but I left shortly after he did and didn't get a good feel if the lock-outs had stopped.
What other things should I check when I am down later this week? I wondered about cleaning / or testing the flame sensor but when I mentioned this to the tech he said that if it were the flame sensor the problem wouldn't be intermittent.
Thanks in advance for any help and kudos to a great site!
kc