[coreyclark]

Very strange indeed. Since the service man already replaced the circuit board which did not help and then replaces the gas valve which then allowed the furnace to operate normally for two weeks before the problem started again I have just about exhausted what I can tell you to do from here since the only part you can check next is the pressure switch mentioned by KC13 in his post above.

I did not mention the pressure switch before since I figured you did not have a electric meter to measure resistance across the contacts when the small furnace draft fan is in operation. If you have a meter or can borrow/buy one you can test the pressure switch which is part number 41 on page 4 of this link.

http://igate.northernplumbing.com/pa...anMfg/GMS8.pdf

The pressure switch is attached to the furnace and has a plastic tube attached to it.

I do own a digital multimeter (Christmas present from a friend who always looked out for me with tools.. ). So here goes the questions... :D

Have AC/DC switch: presume AC
Dial has the following areas: F, V, A, O(with feet): presume the later (O with feet)
Settings in ohm; 20M, 2M, 200K, 20K, 2K, 200: Not sure here, or does it matter. I presume any number is not good.

When you indicate to measure when the small draft fan is on. I presume this is the first fan I hear when the unit begins the heating process?

[Mikie D]

20 ohm fine, test all limit switches firsy when you touch leads together meter should read 0 that's continuity take wires off limits and test all should read zero. Now the pressure switch should read open not zero,Then start furnace and 5 sec after first draft motor starts ,test press switch and should close or zero meaning made then let us know

[coreyclark]

20 ohm fine, test all limit switches firsy when you touch leads together meter should read 0 thats continuity take wires off limits and test all should read zero. now the pressure switch should read open not zero,Then start furnace and 5 sec after first draft motor starts ,test press switch and should close or zero meaning made then let us know

Pardon the rookie question, 20 ohm meaning 20m? If so, results:

Test with Leads on Switch = 0
Test wires attached to switch = 0
Test switch with no wires = no change in digital reading

Test switch after power on of furnace (no wires attached, correct?) returns to zero after approximately 2 seconds.

Standard operation?

[KC13]

It seems as though you are not reading anything beyond the most recent post. Good luck.

[coreyclark]

Don't mean to be rude, but I have read all the posts. Your second post concerning the timing of jumpering the pressure switch came as were were discussing the aux limit control jumpering. Since that time, I the discussion has migrated to the pressure switch. Specifically, checking for resistance on the pressure switch. Does the last test satisfy the question about the functioning of the switch? If not, then I presume the draft inducer is the first initiated process after the t-stat calls for heat?

Sorry for all the rookie questions but it is frustrating to have this when our service is stumped about the issue.

Again, thank you all for your generous assistance.

[coreyclark]

Finally got a call from the service man. He contacted the Goodman company and they want to have the pressure checked from the gas line into the furnace. Goodman indicated that the newer models of gas valves need less pressure than their older counter parts. The service man is coming out tomorrow. I'll post back with the results.

Thanks again for all the responses.

[hvac1000]

Are you on Natural gas or propane?

[coreyclark]

Natural gas.

[hvac1000]

Your quote (The igniter will not stay lit long enough to ignite the gas. The process starts blower comes on, click, igniter lights, igniter goes out, you hear the gas released but obviously does not ignite the burners.)

It will be interesting to see how this works out.

[coreyclark]

Well what do you know. The service guy came back today and the Goodman contact was correct. The gas pressure was set to high. He throttled it back to the appropriate pressure and it worked. He tried it multiple times just to make sure. So, it is working... for now.

Now the interesting question... Did we really need to replace the board and gas valve? Guess we'll never know.

Thank you all for your information and assistance.

[Mikie D]

I highly Doubt it I can tell you how many time techs set up new and old furnaces and never put there manometers on them. Mikie D

[mygirlsdad77]

Glad you got it fixed. Sorry I wasn't there to check pressures. This is common. High pressure on newer vavles will not let valve open(sometimes letting them open a few seconds too late, after igniter has shut down).

[hvac1000]

I have had a service person out and after he checked all the switches and bypassed all parts, indicted it was a faulty circuit board. His return trip to install the circuit board was not successful. The furnace fired once and then back to the cycling. He then replaced the gas valve. At the time this appeared to resolve the issue.


When he replaced the gas valve he did not do what servicemen are supposed to do and adjust the gas pressure as part of the service. You always check and adjust the gas pressure as part of the service and check out or when replacing the gas valve.

BTW It does not make a difference if it is a old or new gas valve as far as the pressure goes. The correct operating pressure is listed on the furnace information tag along with the model numbers and you always adjust to that pressure since that is what determines the firing rate/BTU's per hour heat capacity.

When standard routine's are not followed this is what happens and you had to pay the piper for his mistakes. At least you got it going.