# Furnace problem



## 89468

Just got back from a trip to Norfolk. The weather was varied (to say the least) and one night it got a bit chilly, so I tried to get the furnace going. The main fan came on OK, but after several minutes the system shut down. I tried several times, in case I needed to purge the gas line, but the same thing still kept happening. I took the outside inspection panel off to see if I could spot any problems and tried again to get the furnace started. I could smell gas OK and I could hear the igniter clicking, but still the thing wouldn't light. Then I noticed that the circuit board had a diagnostic LED which was flashing a sequence. A sticker on the furnace had a key for interpreting the code, which turned out to mean, 'Ignition Lockout Failure'. I don't have a clue what this means or how to go about rectifying the problem. Does anyone have any experience of such a failure, or know how to fix it?


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## Superk

Hi I don't know how to fix it but here is how a lockout occurs:

Tthere are three parts to the ignition system, the control board, the electrode wire, and the electrode assembly..

The fan speed has to be such that enough volume of air is flowing so that the sail switch can sense the air flow and tell the control board it has air airflow.. So it will turn on the gas. At the same time the control board will send high voltage via the electrode wire to the electrode assembly. The voltage seeks a ground between electrode and ground probe and a spark occurs. The spark then ignites the main burner. 

If no flame is sensed then the control board performs a lock out turning off the gas.. I do not know how the logic works in your furnace but on some the thermostat has to be turned off and the fan completely stopped to free the lock out.

The problem could be anywhere along the various routes - check the wiring to the circuit board and other connections maybe you shook something loose. Purge the gas via the cooker to make absolutely sure - is the fridge running OK on gas?

Here are some other recommendations I have gleaned from elsewhere:

Make sure your connections are proper, electrode wire and sensor wire properly routed and in good condition and the gaps are within tolerance. Then turn thermostat off with till fan stops and turn on the thermostat.

Clean circuit board contacts. Remove connector, use preferably a white eraser and clean contacts. Apply some de-ox compound to connector and reinstall. (My comment -You can get a spray cleaner from electrical specialists.)

You should be able to hear the igniter clicking as it tries to fire. after about 3 atempts to ignite it will go into a lockdown mode and you have to start all over. are you sure the air tube is clean? is it adjusted per the manual.

Had the same problem fan would run, but no heat. I pulled the electrode out and the space was 1/4" so I changed that put it back in an the first time it clicked it fired up.. HEAT at last.

Hope some of this helps.

Regards.


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## 89468

Thanks for the ideas. It gives me something to look for.

From the sound of it, the problem is that there is no spark occurring. I can definitely smell gas, so don't think this is the cause. I can also hear a distinct clicking sound, which I take to be the ignition system trying to create a spark (an interesting point is whether the sound I hear is an actual arc occurring, or just the sound of a relay activating).

I haven't dug too deep into the system yet, but will take a closer look and see if anything appears to be disconnected or if the spark gap seems too big. The main problem at present is that having looked at the unit a couple of times already, it seems to be fairly well sealed. I haven't spotted where the electrodes are and don't have a manual to guide me. I guess a closer inspection with a torch might reveal something.


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## 89468

I took another look at the furnace today, but got no further in finding out what the problem is. The fan is running and gas seems to be getting through and I can hear a definite clicking sound, which I assume is the electrode sparking.

I got the details of the make and model (Atwood Mobile Products, Model 8531-IV-DCLP) and managed to find them on the web. I've sent an email asking for advice and also if they could send me a manual, so I guess I'll just have to sit and wait now.


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## 88926

I had a chap in the states rambling on about his furnace and the problems he had with it not firing up,to cut a long story short he found that the circuit board was damp and the earth was shorting across the board and he dried his and sprayed it also covered it for the future.Dont know what sort of furnace he had but it was the same as mine (not in the motorhome at the moment so dont know what mine is).It might be a quick fix hopefully good luck


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## 89468

I've checked the unit out a bit more thoroughly, but still can't find the problem. It's an Atwood Mobile Products furnace and I managed to get the model and serial numbers. They have a pretty good web site, so I sent them a technical query last week, but so far they haven't replied. They also have a page that lists pdf's of all their manuals, but Murphy's Law is at work and none of them will download. I'm going to try phoning them later today, to see if I can get them to email or post me one.


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## johnsandywhite

Hi *Gewitty*. These furnaces are prone to having problems with the original fitted circuit boards. My old Coachmen started having a similar problem (although a much older version) and I found it was a resistor with a broken connection on the circuit board due to it corroding over a period of time. I remade the connection and everything carried on working. Another thing that it could be is the Sail Switch which is is the air duct.

>> HERE << is a good link to check out the system. :wink:


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## nukeadmin

A friend has let me know the following 
"The circuit board is down and will need replacing, no doubt whatsoever. Leisure Vehicle Supplies 01543 577334 fax 01543 570177 will have the part that she needs in stock and will confirm my diagnosis."

HTH Gewitty


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