Pressure switch closed trouble code

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Old 01-20-15, 06:50 PM
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Pressure switch closed trouble code

Hello,

I need help on my furnace. First off the thermostat is not get 24v when I tested the W wire....only giving me a 22v reading on the W wire.

The other wires seem to be okay... they are getting 27v reading.

Also the red light is blinking 3 times = Pressure Switch Closed. Not sure why its closed.

What should I check?

I have a Tappan Furnace and the Control Circuit Board 903106 and 632212 Pressure Switch.

Thanks for any help.
 
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Old 01-20-15, 06:53 PM
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Welcome to the forums.

You can't check for voltage at the thermostat. You are showing near 24vac so your 24v supply is good. You didn't tell us what you have for a furnace. A model for the furnace would be a big help.
 
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Old 01-20-15, 07:17 PM
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Old 01-20-15, 07:22 PM
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Thanks! I posted the diagram for it. Its a Tappan Furnace, Where do I find the model number?



 
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Old 01-20-15, 07:39 PM
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The model number should be there.

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Old 01-20-15, 07:41 PM
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http://www.nordyne.com/Literature/708291b.pdf

It is a Nordyne G6RA045C furnace.
 
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Old 01-20-15, 08:17 PM
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Yes! its a Nordyne G6RA045C - 08

I just need to find out why the Pressure Switch is Closed? What is causing it?
 
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Old 01-20-15, 08:43 PM
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In the picture below is your pressure switch. First I would try disconnecting the rubber tube to see if the switch reopens. If it does then there is a clog in that line.... most likely where it connects to the draft inducer. You can use a paper clip to make sure the inducer hole is clean.

If removing the rubber line didn't cause it to change status.... try gently tapping on the pressure switch and see if that clears the code.

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Old 01-20-15, 09:54 PM
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When disconnecting the rubber tube I got 2 blinks from red light. I checked inside the hole and all seem to be dry and clean. tapped on the pressure switch still not working.
 
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Old 01-21-15, 06:54 AM
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When trying to restart the furnace the inducer comes on, but the ignitor don't lights up, then the LED starts blinking 3 times, the inducer shuts down for a few seconds. Then the process starts all over again.

When I tested about 2 days ago the Ignitor was fine. Does the error code not letting the Ignitor to light?

So do you guys think its the Ignitor or a Pressure Switch issues?
 
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Old 01-21-15, 06:59 PM
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I would clean out the barbed fitting from the furnace to the pressure switch and inspect for signs of water in the pressure switch.

I would measure the vacuum to the pressure switch. If it is greater than .5 " water column, I would replace the pressure switch.
 
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Old 01-21-15, 07:25 PM
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You disconnected the rubber hose and got two flashes instead of three. You witnessed a change of status. That is telling you that the hose is probably plugged at the inducer end. You'll need to probe inside the barbed fitting like Houston mentioned. It's only a small hole and easily plugged.
 
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Old 01-21-15, 08:12 PM
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I look inside the hole in both the inducer end and the pressure switch end they seem to be clean and dry. I went and stuck a paper clip inside the hole in both end to clean anyways. Not thing came out or stick on to the paper clip. I taped the switch with the bottom back of a screwdriver and that seem to work. You guys think the pressure switch is going bad?




 
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Old 01-21-15, 08:18 PM
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At this point we would measure the amount of vacuum on the port. If you don't have a vacuum gauge.... change the pressure switch.
 
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Old 01-21-15, 08:27 PM
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I don't have one, I can go buy a vacuum gauge. Which one should I get?
 
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Old 01-21-15, 09:22 PM
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I have a Fieldpiece dual port manometer


and a Dwyer dual port manometer with metal barbs
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but a cheap liquid model should work for this test...

Amazon.com - RadonAway Easy Read Manometer - Fans
 

Last edited by Houston204; 01-21-15 at 09:53 PM.
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Old 01-22-15, 06:37 AM
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I will look into this... Thanks for all the help guys!
 
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Old 01-22-15, 01:43 PM
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Rather than spend $100 + for a decent manometer, just replace the vacuum switch at 1/3 of the cost.

Since you have a meter, disconnect the wires at the vacuum switch and connect the meter to the two contacts- set to the ohms reading. Then remove the rubber tubing from the inducer. Suck on the tubing and you should hear the vacuum switch click and see a change on the ohms scale. If the sound and meter tell you that the switch is working, hook the tubing back on the inducer. Start the furnace with the meter still hooked to the vacuum switch electrical contacts. if the meter shows the switch is not working, you need to find why the inducer is not pulling a vacuum. Could be a clog in the inducer or in the exhaust pipe.
 
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Old 01-22-15, 07:19 PM
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okay thanks, where is the exhaust pipe?
 
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Old 01-22-15, 07:27 PM
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so discount the 2 wires form the switch and connect the black and red meter leads to it? Then suck on the rubber tube till I hear the switch clicks on and watch for changes in the meter? Okay If the pressure switch is discounted how is it getting power? Is there a video or something I can see how its done?
 
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Old 01-22-15, 08:21 PM
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The pressure switch closes the circuit between the 2 terminals when a vacuum is present.

It is easier to perform that test when your meter leads have alligator clips.

Set your meter for continuity and touch the leads together to hear a beep.

Turn off power to the furnace and disconnect the furnace leads to the pressure switch.

Connect the meter leads to the 2 terminal and create a vacuum on the pressure switch to make it close the circuit and cause your meter to beep.
 
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Old 01-22-15, 08:52 PM
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okay so i create a vacuum by sucking on the tube correct?
 
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Old 01-23-15, 06:38 AM
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27.7 inches water column = 1 psi.
That pressure switch is closing the circuit at ~ 1/2" WC.

Be careful not to damage it when testing.

I would first test it while it is installed but unwired. (Careful not to allow the furnace leads to touch ground if power is applied)
 
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Old 02-13-15, 06:06 PM
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The heater was working fine for 3 days then was having the same problem again. I replaced the pressure switch with a new one and the heater is still not working.

Same red light is blinking 3 times = Pressure Switch Closed.

What else should I check? Thanks for any help guys!
 
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Old 02-14-15, 02:15 AM
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Many pressure switches have 3 terminals...
Com
N.O.
N.C.

Verify that you are connecting to common (Com) and normally open (N.O).
 
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Old 02-14-15, 04:00 PM
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pretty sure my connecting is right. theres only 2 wires coming off the switch.
 
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Old 02-14-15, 07:34 PM
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N.O and N.C are often right next to each other and easy to confuse.

The 2 wires should connect to Com and N.O.

It would be good news if you could correct this problem by moving a wire.

Does the new switch display a negative pressure number on it?
Did the old switch also display a pressure on it?
 
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Old 02-14-15, 09:29 PM
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The new switch have the word "Com".

should i switch the 2 wires around? It won't damaged anything?
 
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Old 02-14-15, 11:55 PM
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The pictures that I see on Amazon show only 2 terminals an -1.74" wc.
Is that what your new switch displays?
Id that what the old switch displayed as well?

Or did you remove something more like a a -.5" and go back with a 1.74"?
 
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Old 02-15-15, 07:17 AM
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NEW Switch






OLD Switch...

[/URL]





 
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Old 02-15-15, 11:58 AM
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It almost seems as if debris is acting as a check valve somewhere.

If this restriction was in the vent pipe the vacuum would be broken by the heat exchanger side since this is an 80% furnace with metal vent pipe.

It seems like the debris must be in the inducer.

While I would really like to see a manometer tee'd into the pressure switch tubing, we could remove the vent pipe connection to the inducer and shop vac the induced draft assembly that houses the squirrel cage.
 
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Old 02-15-15, 12:27 PM
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so u think there something is inside the Inducer motor assembly?

so remove the vent pipe connection to the inducer and stick a shop vac in to it?

i might have the wires wrong....First i want to try to switch the wires around...will this be safe thing to do...please confirm.
 
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Old 02-15-15, 12:59 PM
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Yes, you can switch the 2 wires to the pressure switch without any problems.

The pressure switch terminals are labeled kinda strangely.

I am confident you would have noticed if you had a third terminal along the perimeter of your new pressure switch that was labeled Com.

Does unplugging the hose to your new switch change the trouble code as it did before?

I suspect rust is in the inducer and it is acting as a check valve.
I would tape a piece of 3/4" hose to the end of a shop vac to clean it. The squirrel cage is fragile.
 
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Old 02-15-15, 01:04 PM
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theres only 2 terminal to the new and old switch as show in the pictures i uploaded
 
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Old 02-15-15, 02:09 PM
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took the Inducer motor assembly out and vac the whole thing.

Still having the same issues.


let me know if you see something?




 
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Old 02-15-15, 02:12 PM
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maybe it's the control board?
 
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Old 02-15-15, 02:51 PM
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Not sure if this Micro Switch have anything to do with it. This was just setting on top of the furnace. Its connected to the brown wire with the red arrow pointing to it. It's alway been sitting on the of the furnace.

Can someone tell me why its there and what its use for?





 

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  #38  
Old 02-15-15, 03:32 PM
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That is part of a broken float switch.

I didn't mean to disassemble the inducer, just take the pipe off and vacuum with a hose on the end of a shop vac.

It looks like you were able to accomplish this without damaging the gasket material.

I will have to go back and reread the 37 posts to find out if the pressure switch has been tested with a volt meter.


If we get 0 volts across the 2 pressure switch terminals with a heating demand but we measure 24 volts from one side to common, it is not the board.
 
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Old 02-15-15, 04:03 PM
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I'm going to text the pressure switch...I put my meter on the "V" correct?

 
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Old 02-15-15, 04:39 PM
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Yes, put your meter on V.
If DC is displayed, press the Select button.

We want 0 volts across the pressure switch when the inducer is running and we want to see 24 volts across the pressure switch if it is open when the circuit should be closed.

The control board sees a closed circuit across the pressure switch when it should be an open circuit.

I the voltage setting 24 volts indicates potential, so the pressure switch is open.
0 volts indicates a closed circuit if we have 24 volts to one side of the pressure switch to common.
 
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