Miller furnace problem(s)

[Paula39]

We have a 15 year old Miller furnace model # CMF 80-PG-DI-N, serial # CMF 9203-01619. It is a hot surface ignition, LP. For awhile now we have had an intermittent problem. At times the induced draft motor will come on and just run and run (we'll wake up during the night cold and hear it running for example), and it won't ignite. If we open the door for several minutes or so, and close it which kicks in the IDM (triggered by the button when door is shut) it will then continue to ignite and the blower starts. Thereafter it runs successfully for days or weeks again without a problem. From what I have learned the pressure/ centrifugal switch may be a problem? Our gas company is no help, and no one seems to want to work on a mobile home furnace around here. We have replaced the hot surface ignition on their suggestion (two years ago) but still the same problem. We have cleaned the blower assembly and filter is clean and new. Other than that the furnace seems to run normally other than the heat does not feel warm enough from the vents. I have been told that is just a downfall of using LP. Thare are no obstructions in the ductwork or holes that can be seen (looked with flashlight/mirror), and our skirting is insulated (other than skirt venting). The nearest Miller contractor is hours from us. We would appreciate any suggestions as to what parts may be needed. Thanks!

[hvac1000]

((and close it which kicks in the IDM (triggered by the button when door is shut) it will then continue to ignite and the blower starts. Thereafter it runs successfully for days or weeks again without ))

Could be this switch? Jump it out and run it for awhile to see if it is the problem.

[dan-o]

I have the same exact problem. I change the hot surface ignitor module (it is a Honeywell part #S8910U 1000) and that will fix it for a year or so then it will start again if you find a permanent solution please let me know

[Paula39]

dan-o,
I was surprised to see my post from October bumped up and I read your message. We had replaced the HSI as well a few years back, but it never helped us. Not sure if this may help you but I'll tell you what happened to us. After this intermittent problem we had, I came home from work to find no heat at all. The furnace would not ignite at all. We had to replace the ignitor bar of course (seems to fail easily) as there was a crack in it. But upon inspection when the ignitor bar was removed we noticed a small amount of soot (I guess it would be in the burner chamber itself) and this circular metal piece attached at the end of the burner tube that contains the ignitor was damaged. It is called the air cone assembly. It seems that this piece would affect the air combustion to the burners. Something wasn't right concerning combustion so the furnace was going into lockout for safety reasons. That was why we had to open the door to "reset" the furnace.We cleaned out the bit of soot and had the ignitor bar and air cone assembly replaced. It has been working like a charm since. We were thinking it was the draft motor/centrifugal that we'd have to replace but it seemed to come down to proper combustion. Maybe you could have it checked out. Good luck.

[dan-o]

thanks i will try that much appreciated Dan-o