blower starts and stops, flame stays on

[tfrohliger]

I have a Coleman Evcon Presidential 7970c856.When the t-stat kicks on everything starts out fine but after a minute or 2 the blower shuts off and the flame stays on. The t-stat hasn't reached temp yet so everything should still be running. and a short time the fan will come back on. It keeps doing this until it reaches the set temp and t-stat kicks everything off. witch never happens. i thought a temporary fix would be to turn the fan switch to on but the air coming from the vents never seems to be hot enough now to heat the house witch have something to do with why the blower is shutting off. The flame is working but just not hot enough for some reason. this happened 1 other time a few months ago when it got really cold like it is now. (Indiana low teens and lower) almost acts like it is drawing to much cold fresh air in and not letting it heat up enough. Whats your thoughts on this? Sorry for the book! LOL

Thanks,
T.J.

[Robert]

Blockage in burner, burner orifice, gas valve problem, gas pressure improper, faulty fan switch.

Variation of what it could be and may be a combo.


I would test fan switch and also get get inlet and manifold gas pressure checked.


Thanks,
Robert

[tfrohliger]

I had someone come out and fix it. They basically said it was because my furnace is old. They made an adjustment to the flame. They said that it is a 2 stage burner and the spring inside is getting weak. but when they would adjust the flame to where is should be it knocks out the pilot light for some reason. so they had to back the flame off just a little and now it works fine but the flame is a little orange and not really blue like it should be.

[Robert]

The burner flame should be blue. If spring is weak in gas valve, gas valve can be replaced.

I would check air to gas mixture and combustion air .


Sounds like they are more interested in selling a new furnace.


It is old, but if safe, can still be used with available parts.


Thanks,
Robert

[tfrohliger]

The insides are starting to rust so i would feel safer having a new one soon anyways so i don't want to put a lot of money into this one. Thank you for watching out for me though.

[tfrohliger]

also when i looked up the burner on your site it says "No longer made. Limited to stock on hand." That sounds like a good hint that its about time for something that they still make parts for

[Robert]

Yep, LOL. I like for folks to have time to decide and make good choices on human comfort and costly investments.


Wouldn't suggest putting any large sums in it because it is old and parts are hard to come by.


Do your homework and don't allow anyone to pressure you into a quick buy.



You're very welcome, happy to assist.



Take care and best wishes,
Robert

[drumgayjr]

I too have the same problem with Coleman Evcon blower motor. After three winters of this problem I might have finally gotten it solved. I have tended to notice this happening in really COLD weather. Since my mobile home is an mid 1970's CROYDON, insulation is a bit lacking thus the temp falls off quickly causing the furnace to kick back on before things have cooled down completely. The problem was worse when I replace the thermostat with a newer programmable one. The furnace would run lots of short cycles. I changed back to a mechanical bi-metal thermostat. Then to keep it from cycling too quickly, and to make sure the furnace runs long enough to get all the hot air out of the heat exchanger, I matched the the anticipator setting on the thermostat with the amps setting listed on my gas valve ( in my case it was 0.5 ) For the record, this is for a Coleman Evcon 7975C759. I have to gone through 2 nights of near 0 degree weather here in OH and the blower motor has been behaving itself. I won't promise this will cure your problem, but after replacing the filters, both limit switches and the fan switch over the last 3-4 years, this is what I have found to finally get the problem "solved".

Don