11-28-2016, 04:16 PM
11-28-2016, 07:51 PM
It depends on exactly what is happening. The sequence is the blower starts and runs for a set time, then the ignitor starts arcing and the gas valve snaps open (you can hear it), then a flame detector checks for flame which if it finds it within a set time it allows the gas valve to remain open until the thermostat signals for the gas valve to close, then the blower continues for a set time. If the flame detector doesn't signal that it sees flame soon enough the gas valve closes. If the overtemperature detector detects high temperature the gas valve shuts. If the airflow detector for the blower doesn't report sufficient airflow the gas valve closes.
So if the blower starts, runs for a while then stops for awhile before doing this again it could be any one of several things. To figure out which it is you have to get up close to it to see where in the cycle described above things come to a halt. Is the ignitor arcing, can you feel and hear the gas valve open, do you hear the flame ignite, can you see flame, etc. I had an instance when mud daubers had filled the blower scroll to the point where the airflow detector wouldn't actuate so the gas valve never opened and the ignitor never arced. It sounds complicated but if you get up close and personal with the furnace you will pretty quickly figure it out.
So if the blower starts, runs for a while then stops for awhile before doing this again it could be any one of several things. To figure out which it is you have to get up close to it to see where in the cycle described above things come to a halt. Is the ignitor arcing, can you feel and hear the gas valve open, do you hear the flame ignite, can you see flame, etc. I had an instance when mud daubers had filled the blower scroll to the point where the airflow detector wouldn't actuate so the gas valve never opened and the ignitor never arced. It sounds complicated but if you get up close and personal with the furnace you will pretty quickly figure it out.
11-29-2016, 05:34 AM
I can hear the click and see it ignite but soon after it ignites it quits.
This one is a real paint to get at under the sofa which means removing it in-order to get at the unit.
This one is a real paint to get at under the sofa which means removing it in-order to get at the unit.
11-29-2016, 07:42 AM
Brad: it sure is a pain to get at these furnaces.
If it ignites and then shuts down quite quickly I would suspect the flame detector as it is the first thing the board checks following ignition. It wants to ensure that you aren't filling the furnace with propane that should it subsequently ignite might blow the furnace apart.
I can't recall exactly how accessible everything is. If possible check that the flame detector is working by measuring voltage at the control card. If that isn't possible I would suggest pulling the furnace and cleaning the wiring connections at the detector and at the control board. If that fails to correct your problem I'm guessing you will need a new either a new detector or a new control board. Many RV dealers have the ability to test the board and if you have it out it might be worthwhile having tested just for assurance. For the 77 coach I used to have replacement boards were available.
In summary: I think the flame detector signal isn't being received by the control board and that it is likely the spade connectors at the detector have high resistance. The flame detectors are still working in the 77 coach as far as I know so I'm inclined to think yours are too.
I hope this helps
If it ignites and then shuts down quite quickly I would suspect the flame detector as it is the first thing the board checks following ignition. It wants to ensure that you aren't filling the furnace with propane that should it subsequently ignite might blow the furnace apart.
I can't recall exactly how accessible everything is. If possible check that the flame detector is working by measuring voltage at the control card. If that isn't possible I would suggest pulling the furnace and cleaning the wiring connections at the detector and at the control board. If that fails to correct your problem I'm guessing you will need a new either a new detector or a new control board. Many RV dealers have the ability to test the board and if you have it out it might be worthwhile having tested just for assurance. For the 77 coach I used to have replacement boards were available.
In summary: I think the flame detector signal isn't being received by the control board and that it is likely the spade connectors at the detector have high resistance. The flame detectors are still working in the 77 coach as far as I know so I'm inclined to think yours are too.
I hope this helps
12-03-2016, 06:48 PM
Jon, you were correct about the flame detector.
I viewed many youtube videos about similar problems but on house units. Not much on rv units so figured home units are similar and sure enough it was a common problem in home units to have bad flame sensors. I removed and cleaned what was probably almost 30 years of build up on the rod and now it works just fine. Now to do the other unit under the sofa, the worst of the two but no rush for now as the one running keeps us comfy here in the Arizona desert.
I talked to many rv techs and none pointed to this as the problem and most said they wouldn't touch it as most of you are aware the Duo therm has a bad rap for burning down rigs.
This problem started intermittently over the past few years and got to this point of not firing up and staying on so if others have similar symptoms and have not cleaned the flame sense rod that may well be the problem. It is supposed to be in the annual maintenance list.
I almost decided to change over to Atwood at a huge expense but no need to now.
Brad
I viewed many youtube videos about similar problems but on house units. Not much on rv units so figured home units are similar and sure enough it was a common problem in home units to have bad flame sensors. I removed and cleaned what was probably almost 30 years of build up on the rod and now it works just fine. Now to do the other unit under the sofa, the worst of the two but no rush for now as the one running keeps us comfy here in the Arizona desert.
I talked to many rv techs and none pointed to this as the problem and most said they wouldn't touch it as most of you are aware the Duo therm has a bad rap for burning down rigs.
This problem started intermittently over the past few years and got to this point of not firing up and staying on so if others have similar symptoms and have not cleaned the flame sense rod that may well be the problem. It is supposed to be in the annual maintenance list.
I almost decided to change over to Atwood at a huge expense but no need to now.
Brad
12-04-2016, 06:01 PM
Brad: I'm glad it worked out for you. I also appreciate you filling us in on how it turned out. Kudos!
12-04-2016, 08:14 PM
(12-03-2016, 06:48 PM)Brad Townsend Wrote: [ -> ]Jon, you were correct about the flame detector.
I viewed many youtube videos about similar problems but on house units. Not much on rv units so figured home units are similar and sure enough it was a common problem in home units to have bad flame sensors. I removed and cleaned what was probably almost 30 years of build up on the rod and now it works just fine. Now to do the other unit under the sofa, the worst of the two but no rush for now as the one running keeps us comfy here in the Arizona desert.
I talked to many rv techs and none pointed to this as the problem and most said they wouldn't touch it as most of you are aware the Duo therm has a bad rap for burning down rigs.
This problem started intermittently over the past few years and got to this point of not firing up and staying on so if others have similar symptoms and have not cleaned the flame sense rod that may well be the problem. It is supposed to be in the annual maintenance list.
I almost decided to change over to Atwood at a huge expense but no need to now.
Brad
HI Brad, I planning on coming to Quartzsite and Yuma Feb and March any suggestions on when to come and what to do! Thanks Ron
12-05-2016, 05:42 AM
Hi Ron, There are many off road trails in both areas. Do you know about the big show in Quartzsite on Jan 21 thru 29.http://www.quartzsitervshow.com/rv/rv-general-info/.
You plan on boondocking or getting hookups?
Yuma has everything one needs plus you can tour a few places of interest. March is warmer than Feb but either is better weather than most the country.
Email me for further contact. [email protected]
Brad
You plan on boondocking or getting hookups?
Yuma has everything one needs plus you can tour a few places of interest. March is warmer than Feb but either is better weather than most the country.
Email me for further contact. [email protected]
Brad