[thecrowx]

I am the third person attempting to repair a problem with a Intertherm 1155 natural gas furnace, manufactured in '73. The problem is, that the pilot extinguishes when the burner shuts down. Someone else has replaced the gas valve with a universal type. The vent tube is in place, in the pilot assembly, but it is not connected to the gas valve vent port. It is too short, so someone just left it unconnected. Does this have to do with the problem of the burner taking out the pilot during shut down? I have replaced the entire pilot assembly and thermocouple with a factory replacement. It has a nice blue flame, encasing the upper third of the thermocouple. How important is the vent tube in the operation of the cycle of the burner? Thank you !

[hvac1000]

Answer this question first. Is this furnace located in a Mobile home?

[thecrowx]

Yes, it is. Thanks for responding.

[wmproop]

At 37 years old,, the furnace is way past time to replace. There is a good chance the heatexchanger could have holes and the blower fan is blowing out the pilot light,, I would have it checked by a professional . Me personally I wouldn`t feel safe until I had it checked out

[mgliue]

Be careful. Close the manual gas valve, put the fan on, light a long match and introduce it in each burner with the blower running. If your match "dies" your furnace is "dead". Your heat exchanger is cracked. Don't try ,if it happens, to start your furnace again. Intoxication with CO can result.

[thecrowx]

Thank you mgliue, but the way the burner is set up is: It has a single 3/8 tube from the gas valve to the center of the unit. At the end of the pipe, on the top of the pipe, is a single orfice. The pilot assembly sits next to it. Then above the single burner/pilot assembly is a cast flame spreader. There is no heat exchanger. I have checked the fire box for cracks, and it seems to be in pretty good condition. No sign of overheating. What now?

[Dennis1523]

You have a heat exchanger. You do not know enough to be doing anything safely with this. You do not even know what a heat exchanger is. That's OK. But this can kill your whole family in the house. Get smart and spend $45 bucks for a pro to look at it.

[mgliue]

Yes there is one. The heat exchanger is a part that separes the cflame side from the clean warm air, just to explain you better. If you do not see it is just beacause you don't know what it is, but it is there for sure. If its craked de combustion products are just going into your house directly. And innto your family lungs and you know the rest. You have a very old furnace. Normaly 20 years old is enough for a furnace. Then you scrap it. Some times old models use to be tough, but one day are finished. Take care.

[Dennis1523]

Turn the fan on and put a smoke test in the fire box which is what you call the heat exchanger. Then have people or yourself run to every vent and see if you have smoke or smell coming out of the vents. I was just thinking you may also check that the front panel is on right and or that the furnace is not exposed to wind or air from its self such as a air leak blowing on the pilot. One other thing is that the pilot assy could be in the wrong position so just bend it a little tor ward you and check it to see if it works. But be careful if you smell gas or it takes to long to ignite the burners, turn it off and bend the pilot assy the other way and let it air out before trying again.

[thecrowx]

This is a updraft furnace. A single burner sits at the bottom. The fan assembly sits on top of the unit. There is nothing between the two. Just the inside of the furnace, which is nothing more than sheet metal. I have always called it the firebox, but I guess the correct term is heat exchanger? I always though of a heat exchanger as a series of coils. There is no cracks in the firebox, no warping of the metal, no burned areas. The gas company came out, inspected it, reduced the gas pressure, lit it, and left. It has been working fine now. Thank you guys for your help.