goodman gas furnace not lighting

Paul_69

Hey guys, had a goodman gms80403an-12040013772 furnace. tech support said to replace board and we did. whats going on is inducer goes, glows,and hear gas valve click a bit and flutters, have good gas to unit.if i put 24volt direct to gas valve it opens properly and dumps gas out. i tried jump all interlocks and read 24 vlts to gas valve for a couple seconds. another tech support said harness,another said no. we widened pin connections on board plug also.They kept bringing up bad ground.The unit is almost 5years old as well as the home.Could this be the problem?I told home owner to get electrician to prove that ground is in tact from panel to attic furnace. They still have no heat and the tech support seems to be all over the place and we are running out of things to check.Any help would be very helpful as we are getting frustrated! thx

Paul_69

anybody? tim etc...

JUGHNE

With furnace circuit breaker OFF check for any voltage between white neutral and green/bare ground...should be almost nothing.
Then check for any resistance on those 2 wires, should be almost zero. Should be zero from bare to furnace steel also.
(If the furnace blower runs OK on fan switch then neutral is most likely good)

Also need good ground connection between board and furnace ground/chassis/burners.

Did you change or clean the flame sensor?
If no FS then HSI acting as sensor and I would change HSI.

Ironman

I assume you cleaned/checked the flame rod?

If you suspect a bad ground between the furnace and the panel, temporarily ground the neutral wire to the furnace cabinet. If that fixes it, then you do have a bad ground. If not, look elsewhere.

Are you sure the pressure switch is not fluttering when it fires?

Paul_69

its not firing, it attempts to pwer gas valve,but it seems weak. you can feel it flutter the valve but no light off, like i said if i put 24 vlts directly from trans. to gas valve it opens fine.

Paul_69

If its not even lighting, how can it be flame sensor?

Ironman

Jump the pressure switch AFTER the inducer is at full speed and see what happens.

Paul_69

did that also thx
jumped all the interlocks many times

Paul_69

Bob, thx for all the advice..it could still be a poor ground it looks like. i have had a few boards do this same thing but i put a new one in..it is acting like that weak kind of ghost voltage the happens sometimes like the board breaking down or a dirtyswitch or contact you know what I mean? I will try that nuetral to the cabinet when i re-group and go back to job

upstateben

I had a similar issue recently on a gms80 furnace. I traced problem to bad aux limit. Its mounted down on the blower. I would get 24 volts to with wires off the valve but would only get a few volts with the wires on the valve. Valve was doing the exact same thing you describe. That limit was in series with the valve.

Ironman

Paul, you can just wire nut the ground and neutral together in the furnace.
I'd also check what Ben said. I kinda doubt that it's a bad ground from what you're describing.

ChrisJ

If you jumped all of the interlocks and it made no difference, what's left in the circuit besides the control board and the gas valve?

If you're 100% sure the new board is good, I would question whether or not the transformer is supplying enough current (voltage dropping too much under load), or, if the gas valve is drawing too much current. Perhaps the control board simply cannot supply the current the gas valve needs at this point, but bypassing it does.

There's nothing else that could effect it is there?

What voltage do you see at the gas valve when it flutters? I would check the voltage leaving the control board to the valve, and the voltage going to the control board under these conditions as well.

That may help you zero in on what's happening.

ChrisJ

Paul_69

Thanks guys, I am ordered a new gas vave as this and the transformer are all that is left other than the new board and transformer...I was getting tunnel vision after a banging my head on this for hours..I will post outcome after I go back. I wish all the parts were the same like on most oil burners so I could swap out parts as trials!

BobC

The only thing I can tell you is to measure the voltage directly across the gas valve, don't try measuring from any other point.

Bob

rick in Alaska

And double check the connectors from the circuit board, especially if it has a molex plug. I think you said you did that, but not sure. If you could put a meter on the circuit board output and another on the gas valve input, then you could see if voltage drops between them when it tries to fire.
Rick

Paul_69

Went back to seen of the crime and I brought a gas valve with me and threw it in and lit fine. The ohms seemed good but not sure why it was bad. maybe just wouldnt stay open and unit shut down? So now they are set. Thanks for all the advice. Just a tiger to pinpoint.

ChrisJ

Paul said:

Went back to seen of the crime and I brought a gas valve with me and threw it in and lit fine. The ohms seemed good but not sure why it was bad. maybe just wouldnt stay open and unit shut down? So now they are set. Thanks for all the advice. Just a tiger to pinpoint.

Not sure.
Only thing that comes to mind is DC resistance often doesn't reflect AC impedance in an inductive circuit such as this.

You're also testing the resistance at a lower voltage than it runs at. It may have lower resistance at a higher voltage.

icy78

Still seems like you must have a voltage issue. The old valve works fine with 24vac so it should work fine thru the controls unless there is an electrical restriction of some kind. The new valve works because it can operate at that reduced voltage and hasn't been damaged yet by the reduced voltage and thus become harder to open. I think the problem will rear it's ugly head again. May take a year or two but it'll return.

ratio

Some times valves get flaky. Whenever I'm there, they work. When I'm not...

JUGHNE

Yes, you are right about the FS. I misread your first posting, thought your had some standing fire.

Did you measure the voltage right at the new valve after it was steady state running? I somewhat agree with icy78.

Md84

I coming across a similar issue except wit spark igniter. It sparks once shuts off induce and all then restarts the cycle instead of locking out it keeps restarting after one spark even after bypassing all switches. Took power off gv. Then cycles normal no flame obviously but attempts to spark continuously till lock out. 

Hooked direct 24 from trans. to gv opens up just fine 

unclejohn

With me it is always the pressure switch with this type of problem. Should be able to jump from PS to MV on the board which would bypass the K8 contacts if you end up with the same issue with new valve.

mattmia2

So did you actually measure the voltage across the valve, preferably with an analog voltmeter since a dmm only takes a couple readings a second and will miss pulsing voltages? Did you put a manometer on the outlet and inlet of the valve if the voltage was constant to check the gas supply and the regulator in the valve? I have read "the gas valve is just fine" twice in here but nothing about what the pressures were.