[MarkwithaK]

Could have a Hall Effect Sensor?

[novice68]

I took one of my office mate's help to post the pictures. Let us see if this link would work.



Let me know if it does not.

Thanks,

[novice68]

Try by putting this link in your browser if the above does not work.


Picasa Web Albums - Ahsan - Heater

Thanks,

[hvac1000]

That is a Honeywell gas valve I believe. There should be 24 volts going to that valve when the unit is calling for heat. Remove the wires and attach your test meter to read the voltage.

[novice68]

Yes, I do get the 24 v in blue wire when I disconnect it from the terminal and connect one end of volt meter to the wire and the other to the terminal. But as soon as I connect it back to the terminal it disappears. May be it is suppose to disappear or it could be the cause of problem.

"I am getting 24 volts going in gas value as soon as I start the heater - I checked this by disconnecting the blue wire and connecting one end of volt meter to the blue wire and the other to the gas valve where the blue wire is suppose to be connected into gas valve. However when I connect blue wire back to the gas valve and then connect one end to volt meter and the other end to green wire, I do not get any reading."

[hvac1000]

If you are getting 24 volts across the gas valve wires and the valve is not opening then I would have to say the valve is defective.

[hvac1000]

Could have a Hall Effect Sensor?

YEP carrier and Bryant use them

[mygirlsdad77]

Need to test across both terminal while supply wires are still connected. If you get 24v now, then your valve is bad. I believe you are testing the connections incorrectly.

Pulling the blue wire and testing between that and the spade that it connects to may give you a false 24v reading. When you put it back on, the 24v disappears. Need to test between the two wires( either while they are both connected to valve, or when they are both disconnected from the valve.)

[T-Top]

Carreir uses the hall effect sensor on the packaged units but not with the split systems. Flame failure= no gas or no gas ignition on the flame sensor. In your case I would say you have a bad valve or very dirty burners and or burner orifice.

[hvac1000]

But do you know the reason Carrier/Bryant does not use the hall sensor on there other equipment. It has nothing to do with cost BTW.

[mygirlsdad77]

Is this a quiz, cause if it is, I'm feeling a little weezy, think ill stay home today.


Is it just me or does it sound like novice is testing the valve incorrectly. Can someone here post some type of picture showing where he should have his tester leads.

[novice68]

I am sure I was testing it incorrectly as I do not know what I am doing :confused: However I plan to go and test using the two wires on the heater with two wires on the volt meter. I am sure I tested that but since I was not getting any reading I thought I was doing something wrong and then tested with just one wire. :( I guess I was wrong the second time.
I gather that if I do not get any reading when testing by connecting two volt meter wires to two wires on the heater, then the gas valve has gone bad. Am I on the right track here?

[mygirlsdad77]

No, if you put two meter wires to two gas valve wires and don't read 24v, then the problem is not the gas valve. If you get 24v reading, then the gas valve is bad.

[novice68]

I tested and retested multiple times and I am not getting any reading when I attach two meter wires to two gas valve wires. I had set the meter to DCV 50 and then DCV 10 but still no reading.
One thing that is puzzling me is that when I do same test on the heater (I have two similar heater as mentioned earlier) that is working I am not getting any reading either. Am I testing correctly? If I'm should I not be getting some reading for that heater that is working?

[hvac1000]

Try using AC and not DC!!

[novice68]

I used AC this time and it confirmed that I am NOT getting any voltage on connections at the gas valve. I did check the other heater and I do get the voltage on the other.
What does this mean and what should be the next step?

Thanks

[MarkwithaK]

Your pressure switch could be stuck closed. If this is the case then on a call for heat the unit will sense this and will not lite. It is a safety feature built in. Try this. Turn the unit off and pull one wire from the pressure switch. Turn the power on and after the inducer starts up then carefully attach the wire you pulled. See if your unit fires. If so then you have a failed pressure switch.

[novice68]

If there is no voltage at the gas valve (I guess this is the pressure switch) would pulling wire and putting it back make any difference?

[MarkwithaK]

Yes. If the units senes that the pressure switch is closed at the initial call for heat then it will not open the gas valve. Again, it is a safety feature.

[novice68]

No. Nothing happened. I pulled the wire and then started the heater, When the inducer started, I put the wire back in its place but the gas did not come and hence no fire.