Ask Experts Questions for FREE Help !
Ask
Page 1 of 2 1 > Last»
    Bougher's Avatar
    Bougher Posts: 13, Reputation: 1
    New Member
    		  
    #1

    Dec 19, 2008, 07:48 PM
    Gas Valve Test Points
    I read another post on here similar to mine. My furnace is on and everything, but cold air is coming out of the ducts. The post said to try tapping the gas valve (in case it is stuck). That didn't work. Also, I read that there is supposed to be 24 VDC on the valve prior to lighting off the machine. My question is: where do I take these readings? Thanks for the help.
    KISS's Avatar
    KISS Posts: 12,510, Reputation: 839
    Uber Member
    		  
    #2

    Dec 19, 2008, 08:02 PM

    24 VAC. Not DC

    Depends on the valve.
    hvac1000's Avatar
    hvac1000 Posts: 14,540, Reputation: 435
    Heating & Air Conditioning Expert
    		  
    #3

    Dec 19, 2008, 08:06 PM
    Post exact model and brand.
    Bougher's Avatar
    Bougher Posts: 13, Reputation: 1
    New Member
    		  
    #4

    Dec 20, 2008, 06:25 AM

    This is what I saw on the sticker:

    SV9501M2528
    Reg 3.5 Adj 3-5 range
    24V 50/60HZ
    0706D3C12 19025475

    I know my problem is somewhere in the ignition area. The rotary pump at the suction is working and air is sucked through the filter. The outlet pumps are working, but cold air is coming out of the ducts. I don't know if I was supposed to see a flame at the ignition area, but I didn't.
    KC13's Avatar
    KC13 Posts: 2,556, Reputation: 99
    Ultra Member
    		  
    #5

    Dec 20, 2008, 06:48 AM

    What you posted looks like it came from a Honeywell Smart Valve control, not the actual model of the furnace.
    Bougher's Avatar
    Bougher Posts: 13, Reputation: 1
    New Member
    		  
    #6

    Dec 20, 2008, 06:50 AM

    Okay. I don't know what that tells me.
    KC13's Avatar
    KC13 Posts: 2,556, Reputation: 99
    Ultra Member
    		  
    #7

    Dec 20, 2008, 06:52 AM
    Quote Originally Posted by hvac1000 View Post
    Post exact model and brand.
    We need more info. It's like telling us your car has Champion spark plugs; okay, but what kind of car is it?
    Bougher's Avatar
    Bougher Posts: 13, Reputation: 1
    New Member
    		  
    #8

    Dec 20, 2008, 06:56 AM

    The label on the case of the furnace says:

    Excel Comfort Systems, Inc.
    Model #: MPGA050B3
    Serial #: 6239940024
    20251801B

    It's a forced air furnace with natural gas
    KC13's Avatar
    KC13 Posts: 2,556, Reputation: 99
    Ultra Member
    		  
    #9

    Dec 20, 2008, 07:14 AM

    There we go... okay, start here: do you have a voltmeter? Locate the pressure switch (typically a small canister, two or three wires and a small hose connected to it), and check for voltage between terminals after inducer starts.
    Bougher's Avatar
    Bougher Posts: 13, Reputation: 1
    New Member
    		  
    #10

    Dec 20, 2008, 07:36 AM

    I see the small hose, but two sets of wires. One set was for control, the other for the ignitor. Also, I don't know where the terminals are. I'm so confused.
    KC13's Avatar
    KC13 Posts: 2,556, Reputation: 99
    Ultra Member
    		  
    #11

    Dec 20, 2008, 07:48 AM

    Confused? Good, that's the first lesson, recognize your disposition-you're well on your way here. Success is one step closer... you are looking at the Smart Valve. Remember this for later. Keep looking for the pressure switch, the hose will most likely be rubber, approx. 3/8" diameter.
    Bougher's Avatar
    Bougher Posts: 13, Reputation: 1
    New Member
    		  
    #12

    Dec 20, 2008, 07:53 AM

    Okay, but I still don't know where the terminals are.
    KC13's Avatar
    KC13 Posts: 2,556, Reputation: 99
    Ultra Member
    		  
    #13

    Dec 20, 2008, 08:06 AM

    Where the wires are connected. If they are recessed into switch body you may have to back the wires off a little. Or, try this: remove the wires and use your multimeter to check for continuity between terminals with inducer running.
    Bougher's Avatar
    Bougher Posts: 13, Reputation: 1
    New Member
    		  
    #14

    Dec 20, 2008, 09:46 AM

    I found a troubleshooting guide for the valve that helped locate the test terminals. It had me check the 24V common to hot, which gave me about 27 VAC. It also had me test 24V common to 24V thermostat/pressure switch. When I turned the P/S to ON, the reading jumped to around 15VAC but dropped back to 0VAC. Is the voltage supposed to stay high like the other? Or is it supposed to drop again?
    KC13's Avatar
    KC13 Posts: 2,556, Reputation: 99
    Ultra Member
    		  
    #15

    Dec 20, 2008, 01:42 PM

    Voltage should be all or nothing. Partial voltage indicates some resistance in the circuit that shouldn't be there. Did you check the pressure switch yet?
    hvac1000's Avatar
    hvac1000 Posts: 14,540, Reputation: 435
    Heating & Air Conditioning Expert
    		  
    #16

    Dec 20, 2008, 03:22 PM
    Quote Originally Posted by KC13 View Post
    Voltage should be all or nothing. Partial voltage indicates some resistance in the circuit that shouldn't be there. Did you check the pressure switch yet?

    Take a look at this to troubleshoot.
    Attached Images
  1. File Type: pdf 2003htgcat_p207-208.pdf (730.7 KB, 264 views)
    2. Bougher's Avatar
    Bougher Posts: 13, Reputation: 1
    New Member
    		  
    #17

    Dec 20, 2008, 06:03 PM

    That is the same troubleshooting guide I was using. The common to pressure switch voltage is what was giving my the spike and 0 reading. It tells me a bunch of stuff to check, but I'm not entirely sure how to check all that stuff.
    KC13's Avatar
    KC13 Posts: 2,556, Reputation: 99
    Ultra Member
    		  
    #18

    Dec 20, 2008, 06:31 PM

    At some point you may have to just bite the bullet and call in a pro. Not all problems can be solved over the internet in spite of the massive conglomeration of infinite genuis available here.:(
    hvac1000's Avatar
    hvac1000 Posts: 14,540, Reputation: 435
    Heating & Air Conditioning Expert
    		  
    #19

    Dec 20, 2008, 07:07 PM
    Quote Originally Posted by KC13 View Post
    At some point you may have to just bite the bullet and call in a pro. Not all problems can be solved over the internet in spite of the massive conglomeration of infinite genuis available here.:(
    Agree
    Attached Images
     
    Bougher's Avatar
    Bougher Posts: 13, Reputation: 1
    New Member
    		  
    #20

    Dec 21, 2008, 10:40 AM

    I called the pros. I told them what I've done so far and they said to see if the pressure switch is clogged. I took off the pressure switch and blew in it and I heard the bellows move, so I know it isn't clogged. I hooked it back up and tried to check for a voltage while the furnace was on, but I got nothing. I am supposed to see a voltage, right?
Not your question? Ask your question View similar questions
 
Page 1 of 2 1 > Last»

Question Tools Search this Question
Search this Question:

Advanced Search

Add your answer here.


Check out some similar questions!

How to test a White Rogers 2 stage gas valve? [ 19 Answers ]

Hi, I have a Magic Chef Furnace with a Robertshaw Ignition Module and White Rogers Gas valve. The problem is that the gas valve will not open to start to flame to the furnace. If you turn up thermostat, I then get spark and then a pilot light. Then nothing. I have replaced the Ignition Module and...

Gas valve test [ 3 Answers ]

Is there a way to test a gas valve on a roof top ac? Seems to me that when I went to AC school ( about 30 years ago) there was a way to check the pressure at a valve using a manometer. Is this possible are what? Frank

No Shut Off Valve between water heater and bathroom sink valve [ 14 Answers ]

I have a constant drip in my bathroom sink. After a little trouble shooting, I came to the conclusion that my hot water valve underneath the sink is the culprit. I traced the pipe down the wall, into the basement and to the water heater. The only thing between the water heater and the old valve in...

How to test gas hot water heater pressure release valve? [ 7 Answers ]

The pressure release valve on the State Select Gas Hot water heater (40 or 50 gallon) is allowing water from the hot water tank to drip through the copper overflow pipe drain on the side of the house. There is no leak or drip around the valve or tank itself. The safety notice on the hot water...

Gas Valve pressure test [ 5 Answers ]

I just ordered a new gas valve for my fireplace. I damaged my old one by blowing compressed air into it to remove spiders that had found their way in through the gas orifice to the burner. Question: how do I test the water column pressure on the new valve, or do I assume it already comes pre-set...

View more questions Search