Flame sense without gas valve

kingbuggy · 03-13-2012, 02:33 PM

Hello,

I have a Janitrol natural gas furnace model number GMH80704BNAB. Up until last Thursday there was a red light on the board blinking 7 flashes which means LOW FLAME SIGNAL. The unit was still heating/cooling okay though.

I now have a red light blinking 5 times which is supposed to mean FLAME SENSE WITHOUT GAS VALVE and no heat is coming out. I had a tech come out and look at the unit free of charge and he said the board was bad. The unit cools fine and the blower works but no heat.

The strange thing is I don't think the ignitor is working. No glowing, no clicking or anything.

Any ideas on what may be wrong with the unit? I just want to make sure it's the board before I have a tech install one.

Thank you for your help.

hvac5646 · 03-13-2012, 04:07 PM

no burner, and erroneous fault codes are usually an indicator of a bad board...but sometimes could be multiple problems

how · 03-13-2012, 04:53 PM

*low flame signal & flame sense w/o valve can also mean a bad valve.

*A poor ground can damage a board and sometimes it will just make it erratic. Check all your furnace ground wires to make sure they are all snug.
Maybe you'll be lucky.

heatingman · 03-17-2012, 02:39 AM

Quote:

Originally Posted by kingbuggy

Hello,

I have a Janitrol natural gas furnace model number GMH80704BNAB. Up until last Thursday there was a red light on the board blinking 7 flashes which means LOW FLAME SIGNAL. The unit was still heating/cooling okay though.

I now have a red light blinking 5 times which is supposed to mean FLAME SENSE WITHOUT GAS VALVE and no heat is coming out. I had a tech come out and look at the unit free of charge and he said the board was bad. The unit cools fine and the blower works but no heat.

The strange thing is I don't think the ignitor is working. No glowing, no clicking or anything.
make sure the flame sensor is sending signal to the board if it is then yes it is a bad board remember that flame sensor is sending millavolts

Any ideas on what may be wrong with the unit? I just want to make sure it's the board before I have a tech install one.

Thank you for your help.

first make sure that flame sensor is sending signal if it is its a bad board remember flame signal is measured in millavolts

how · 03-17-2012, 12:34 PM

Low flame signal for a rectifying flame sensor requires a dcma check to check the flame rod. A visual check of the flame around the flame rod is needed to see if the low signal is caused by a poor flame envelopement of the sensor or not.

Flame sense without gas valve says that a flame sensor circuit signal was being received too long after the 24V to the gas valve power was shut off. A 24V check of the gas valve when the thermostat shuts it off will prove is the gas shut off is instant or delayed.

Either a faulty gas valve or a mother board could cause both of these fault codes.

ben's plumbing · 03-17-2012, 11:10 PM

If you had a tech come out free...he seems like and honest guy..let him install board ..you will then know if it was the board...he was there we are not.....

make sense to me...