Check out some similar questions!

jcroct · Feb 4, 2011, 10:23 PM

Heater start as normal, after 10-15min, burner cut off, another 2min fan stop. Then it starts the heating process right away. It keep cycle like this until reach thermostats setting.
Filter is clean, vent is not clog.
Need your help

repairman_red · Feb 16, 2011, 04:54 PM

Check if control voltage is dropping out to the w terminal. There are two ways to check: 1 use a multi-meter (volt meter) or 2 use a jumper wire from red to white at furnace. If it still persists check the flue for good drafting.

ballengerb1 · Feb 16, 2011, 04:58 PM

Heater, could you be a bit more specific with type of furnace, brand, model

jcroct · Feb 21, 2011, 10:37 PM

It's RHEEM RGPN-07NAMER horizontal type. Got 3 blinks code. I think the problem came from main limit control.
It happen even without cap on chimney. So either no enough power on draft motor, or main limit control over-reactive?
If I close gas hand valve half way, then it run all the way until heat call ends. Can I doing this way to solve this problem?

jcroct · Feb 21, 2011, 10:47 PM

I try it by removed cap of chimney and it is clean. It's horizontal type, about 6 feet long chimney. Could be the drafting motor not power enough or main limit control over-react? The 3 blinks code will end(stop blinking) after burner shout and the fan blow about 90 seconds. If I use less gas by turn hand valve haft way, then no a problem.

repairman_red · Feb 22, 2011, 06:37 AM

Do you have an evaporator coil on the furnace?

jcroct · Mar 11, 2011, 02:22 PM

Yes

mygirlsdad77 · Mar 11, 2011, 04:49 PM

Hi jcroct. Definitely do not close the gas cock part way. It needs to be wide open, otherwise the furnace may carbon up. Gas vavles are designed to have a certain amound of incoming pressure and volume to work correctly. Now, it sounds like you either have overfiring, or lack of air flow. I would suggest having gas pressures checked, and check filter, secondary heat exhanger(if 90+ unit) and evap coil to make sure they are not plugged with dust. Also make sure all supply registers are open and clear, as well as all return grills.

jcroct · Mar 12, 2011, 08:00 PM

The gas company came check the gas burning, he said normal. I open the cover and check the evap coil and heat exchange. There is nothing plug and clean. All piping are open. Filter is clean, even use without filter just for testing.
How much of gas pressure should be? What can I do if the gas pressure is too high?

jcroct · Mar 22, 2011, 09:13 PM

I got gas pressure 7.4" WC

mygirlsdad77 · Mar 23, 2011, 03:15 PM

Is this a propane furnace, or natural gas? And are you checking the pressure on the inlet side of the gas valve, or the manifold side? Nat gas, usually 5-7 inches wc on inlet side, and 3.5 wc on manifold side. Propane, 11-13wc on inlet, 10 on manifold. The pressure is usually adjustable for the manifold side, by taking a cap off on the gas valve(flat cap with strait slot for a standard screwdriver) then there is another screw under that that will adjust pressure, but the furnace needs to be firing to get a manifold reading.

It will say on the furnace identification tag what the pressure should be for your specific unit.

jcroct · Apr 13, 2011, 03:27 PM

I measured temperature around main limit switch. When blinking code show up it reached at about 140F. I bypass this switch and ran for an hour without problem, the measurement stay at about 145F. So I replaced it with new main limit switch, and it took care this problem.

Thanks for all the help!

mygirlsdad77 · Apr 13, 2011, 03:31 PM

Thanks for the update. Glad you got it fixed.