Blower & Pilot on but Ignitors are odd. HELP please

[bambino]

I have the control board of HH84AA011 on my furnace.

I have tested the transformer and have 26 volts.  I have 26 volts across C & R, also on 26 volts from the fusible link and limit switch to ground,  I have 26 volts across my transformer.

My pilot light is working and the blower will kick on but the burners never turn on.

Your help will be immensely appreciated.

Thank you.

[RegUS_PatOff]

has this been working up till now ?

What do you have at:

GAS 1

GAS 2

GAS 3

 

[bambino]

Gas 1 & 3 appear to be jumped together and that is 26 volts

Gas 2 has no voltage reading at all.

Thank you.

[RegUS_PatOff]

[user=3641]RegUS_PatOff[/user] wrote:

has this been working up till now ?

GAS1 & GAS3 together = 26v is OK

GAS2 is Common

then check the voltage at the Gas Valve

[bambino]

Gas valve has 26v on white and 0v on Common.

[RegUS_PatOff]

I'm not sure... Gas valve may be bad...

What model Furnace do you have ?

Someone else on here may know more.

 

 

[bambino]

The furnace is a Bryant/Carrier 394GAD048125 ACEA.  The pilot does work are you thinking the Main Body that feeds the burners?  Is there any way to check the functionality of this?  Safely perhaps??

[dkpd1581]

When you say that the "Blower" kicks on, what exactly do you mean:

1. Indoor Blower Motor

2. Induced Draft Motor

When you are measuring voltages do you have one lead connected to the common of the transformer, to the metal chassis, or some other way, and are checking with the other lead along all the points of the circuit?  How exactly are you checking the voltage.

Typical reasons for a failure like yours could be:

1. Stuck gas valve

2. Open windings (no continuity through) the gas valve

3. Stuck, defective, or misadjusted induced draft motor proving/pressure switch

4. Obstructed flue

5. Obstruction, hole, or kink in rubber tubing to induced draft motor pressure switch

6. Squirrel cage wheel of inducer motor bad and not moving enough air to trip proving switch

7. Need to vacuum exchanger of rust and debris

8. Inducer motor going bad and not moving up to speed

9. Manual reset switch trip or defective auto reset safety switch

Let me know what "The blower kicks in" means exactly and we can go from there.  Is this an 80% or a 90%+ furnace?

Thanks.

http://www.docs.hvacpartners.com/idc/groups/public/documents/techlit/om04-22.pdf

[bambino]

I'm measuring the voltages to chassis ground. 

"Blower Kicks In"

I'll set the thermostat for the heat to turn on.  When I'm standing by the furnace I have the cover off and I will press the cover safety switch for the furnace to be activated for approximately 45 seconds and let go.  I then press it again and the then the fan blower turns on which is what normally blows the heated air. 

Only cold air is being blown thru the house because the burners never turn on.  The pilot light is indeed on.  The furnace is from 1986 Not H/E ( original in this house and has been working fine).  There are no other secondary blowers or rubber tubing.  I have reset the power to the furnace numerous times.

Thank you.

[dkpd1581]

Oki doke a couple of things first.  If you are turning on the heat at the T-stat and then walking to the furnace with the access panel already off and press the door safety/interlock switch, your machine may go into a delay and then the indoor blower motor comes on because the board (assuming it has one) registers that sequence of events as a fault. Some units receiving a heat call from the T-stat upon a power loss and start up go through a different sequence of events than receiving a heat call while power is applied to the unit.

Faults on heat mode always default to the indoor blower motor energizing as a way to remove heat from the exchanger.  The machine might not understand exactly what went wrong or why something weird happened; however, it sensed and "Awe *t" moment and went into "Save me" mode by turning on the fan.

If the same sequence of events happens with the furnace all put back together, door on, everything as it should be then you have to suspect a few things:

1. A limit switch is open or tripped.  The switch could be defective or may require a manual reset on your part to put it back into service.

2. Your control board (again assuming there is one) is defective and not sending 24VAC to the coils of your gas valve.

3. The coils of your gas valve solenoid are open (no continuty)

4. The valve is good but the valve seals are stuck together and the solenoid energized is not enough to pull them open.

5. There is a defective, loose, or missing connection in the circuit.  Maybe a loose ground, poor crimp splice, shove the wire too far into a screw on connection and hit the insulation instead of the actual bare copper connector.

Sounds like you are handy with a meter so with all power to the unit off, find each and every safety (you may have to look a little harder for some) and with the wires removed check for continuity through each and every one.  If you have more than a few ohms (ideally you will have 0 if its good and you are not holding onto the connections with your fingers) then you should consider changing it.

Put all of that back together and then pull the wires off of the gas valve and check for an ohm reading through it.  You dont know what the reading should be; but, you should have some reading and it will prove continuity through the circuit.

Put that back together and make yourself a fused jumper wire (cut and alligator clipped wire in half, splice a 3 amp car fuse into the cut ends of the wire with a crimp on connection or electrical tape if you have to).  Clamp off one alligator clipped side to the R or any known 24VAC source, press the door switch to energize the furnace and controls, and then touch the other end of the now engized jumper to the 24 VAC inlet side of the gas valve.  You should hear the valve snap open or click as you touch the coil side. 

If so then the valve is good and the burners should try and light.  If the burners dont light you may have a gas pressure problem, dirty orafice, or stuck valves.

Try those things and see what happens and then we can go from there.