Need help troubleshooting furnace startup problem.

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  #1  
Old 11-05-13, 12:27 PM
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Question Need help troubleshooting furnace startup problem.

I live in southern California, and we have a Rheem Criterion II gas furnace. MFD.Date 01/2003

The furnace works great. But sometimes (usually when it hasnt been turned on for a few days) it wont start up. Looking inside I see 3 LED's when off 2 right ones are solid green, but when I turn it on and it fails to turn on the middle on blinks 4 times slowly.

After doing some reading online I was told to clean this hose and press red button on starters. The buttons are not depressed, so I cant press them and the hose is clean.

I have noticed however that whenever this happens, if I flick the diaphram box (not really sure the technical name) the heater will start. So it goes something like this

9/10 times heater will start and work fabulously
1/10 times it wont start
a) set it to off
b) take off cover from furnace
c) flick lightly the round thing with my finger, or tap it lightly (see picture below)
d) turn on furnace, it goes on.


How do I fix this? do I need to replace that whole round thing? or can I repair it?

Thanks!



 
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  #2  
Old 11-05-13, 03:47 PM
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Sounds like it may be a loose wiring connection since flicking it corrects the problem. I suggest checking the wiring connections at the pressure switch for tightness and corrosion on the terminals, at the control board and the molex connector that goes through the blower deck.
 
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Old 11-05-13, 04:20 PM
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Thanks for the ideas. Could you go in more detail as to where all of these things are located and what they look like? I know nothing about furnaces and their parts :P
 
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Old 11-05-13, 04:39 PM
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The pressure switch is the part you stated you are flicking to get it to work. It is the black circular item with the red hose and wires attached in the second photo you posted. The furnace control board is the electronic part where all of the wires attach and where you see the LED lights. A molex plug is a plastic plug that has multiple colored wires going into it. The attached photo shows the molex plug going through the blower deck I mentioned previously and the location of the control board. Make sure you turn power off to the unit before touching any wires on the control board or molex plugs.
 
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Old 11-05-13, 05:07 PM
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Thanks I will take a look when I get home... are there any household liquids or tools that are pretty good at cleaning the items you mentioned?
 
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Old 11-05-13, 05:12 PM
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My suggestions involved checking the wiring to see if the connections were fully seated and the terminals on the pressure switch are not corroded. If you do find corrosion on the terminals a light brushing with a small wire brush or even a toothbrush will remove the corrosion. You definitely have no need to use any type of household liquids.
 
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Old 11-05-13, 05:14 PM
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once cleaned would coating it with machine oil or something non water based be a good idea to prevent further corosion?
 
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Old 11-05-13, 05:20 PM
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No, that is not necessary. All terminals and connections need to be dry and clean.
 
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Old 11-06-13, 11:11 AM
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Checked connections, seem to be fine, no visible corrosion, the board also looks fine. Nevertheless I took the wires off and put them back on to scrape way some of the top layer copper with the clips (in case it oxidized or something). Will report back tonight.
 
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Old 11-06-13, 11:32 AM
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I suggest that you clean the port where the red hose attaches to the inducer motor to make sure it is not gunked up. You can use a paper clip or a very small drill bit to clean it. Make sure it is clear from the opening of the port all the way to the fan blade inside the motor.
 
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Old 11-06-13, 01:45 PM
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Im assuming you are talking about the pink/red hose that goes to the round box in my pictures? Clean both ends where it connects?
 
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Old 11-06-13, 02:41 PM
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Yes, both ends but also the port where that hose attaches to the inducer motor has to be clean as described in my earlier post.
 
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Last edited by firedawgsatx; 11-06-13 at 03:13 PM.
  #13  
Old 11-06-13, 03:33 PM
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Ok will do, couple more side questions.

my unit is in a closet type of thing that is basically outside. The only corrosion type stuff I saw was what looks like transformer block made of metalic plates located right underneath the inducer motor port in your picture. There is a slight corosion (maybe rust) on the outside of it. Should I be concerned about that?

overall is there some sort of maintenance I need to do to this heater?
 
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Old 11-06-13, 03:44 PM
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Here is a link to the service manual for your unit:

http://www.allreds.net/WS2/docs/rhe/rgph-man.pdf

Starting on page 30 it outlines maintenance requirements.
 
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Old 11-06-13, 04:00 PM
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Thanks for the Manual, how often should I be changing the filter? The manual says to keep them clean but doesnt really say what constitutes dirty?

Also is there only 1 filter? or should I be looking at more than 1 to clean/change?
 
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Old 11-06-13, 04:05 PM
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How often a filter has to be cleaned or replaced depends on several factors such as how much the system is operated, how much dust/pollen is present in the air and etc. I clean my filters at least once every 30 days. The cleaner a filter is the better the system will operate. I am not sure how many filters you have as I am not there. It should be easy to locate the filter(s). Some people have filters installed at their return air grille(s).
 
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Old 11-06-13, 04:16 PM
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Ok thanks, I will take a look and take pictures if I cant figure things out. Thanks so much for all of your help!
 
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Old 11-06-13, 04:56 PM
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One more tip: when you remove the red hose from the port on the inducer motor gently suck and blow on that end of the hose a couple of times and you should hear a click in the pressure switch. I don't usually advise to do this but this will usually get the unit going again. If the unit works after sucking and blowing on the hose I would suggest you replace the pressure switch to prevent future problems. If you post the model number of your furnace I can assist in helping to find the part number for the pressure switch.
 
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Old 11-06-13, 05:02 PM
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Model Number is: RGPH-07NAUER
 
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Old 11-06-13, 05:19 PM
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The part number for the replacement pressure switch is: 42-24194-82
 
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Old 11-07-13, 10:06 PM
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Nope, cleaned the holes, blew throug hose... when I blow I do hear a click after about a second or two of blowing into it.

I made a video here of the behavior... basically it wont start, I open the cover, tap the black round thing.. it goes on... watch --> Furnace problems - YouTube
 
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Old 11-08-13, 07:20 AM
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I suggest you remove the brown and purple wires from the pressure switch you are tapping on. Then join those two wires together (use a small piece of wire to join them if they aren't long enough to reach). This will bypass the pressure switch. If the furnace operates properly doing this then it is time to replace the pressure switch. Only bypass the pressure switch for testing purposes only.
 
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Old 11-08-13, 11:21 AM
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Ok, Im guessing pressure switch is to ensure there is no problem with gas supply? When I disconnect the wires (to short them), what about the red/orange hose? Is gas still traveling through that?

I was thinking about taking it off this weekend and taking it apart to see if maybe cleaning it would help (not sure if its even possible to take it apart without busting it).

By the way, where would I order a replacement and how much should I expect to pay? (thanks for the part number earlier).

Also, how long should one of these last? Im assuming its the original part, so it lasted about 10 years, is that normal?

Sorry to bombard with so many questions... but side question back to filters... I found a filter in mine its in a slot underneath the furnace... It looks "clean" there is a slight layer of dust on it, but its like part of the filter, it may be just actual filter discoloration, its hard to tell.... its nothing I can clean off by hand of tapping the filter or anything like that.... here are pictures (click to zoom, then click magnifying glass to zoom further).





Is that clean? How do I clean it if its not?

Thnaks for all your help!
 

Last edited by Chrushev; 11-08-13 at 11:44 AM.
  #24  
Old 11-08-13, 11:32 AM
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A furnace pressure switch is a safety device designed to sense the negative pressure created by the draft inducer at start up (to make sure the inducer fan is running) and to shut down furnace ignition if proper combustion air flow is not maintained. The part is usually around $35.00 to $45.00. It is not considered a serviceable item. If you google the part number there are a lot of sources to purchase it. It definitely pays to shop around as there is a wide variation in prices. Do you have a multimeter to do some voltage testing and continuity check on the pressure switch? No, gas does not travel through the red hose attached to the pressure switch. Only a small amount of air pressure created by the induction fan is in the hose. Pressure switches don't often fail.
 
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Old 11-08-13, 11:40 AM
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I do have a multimeter, where would I measure and what should I expect? Also, I was editing my previous post with some more questions while you replied could you look at that post again?

Thanks!
 
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Old 11-08-13, 11:54 AM
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That filter appears to be dirty to me but difficult to tell from a photo. That is a disposable type filter. I would replace it to be safe. Is that the only filter? As far as testing the pressure switch you would set your meter to VAC. Then set your thermostat to call for heat and when the induction motor starts to spin you place one meter lead on one of the pressure switch terminals and the other lead on the other terminal. You should have a reading of 0 if the switch is closed.
 
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Old 11-08-13, 11:58 AM
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Hmm yeah I think that is the only filter, I cant find any others anywhere (all of them would be accessible without unscrewing stuff right) ?

My issues would be unrelated to a dirty filter thought right?

As far as multimeter, I have one like this.

 
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Old 11-08-13, 12:14 PM
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My issues would be unrelated to a dirty filter thought right?
For testing purposes only, you can remove the filter and see how your furnace operates. Of course, you do not want to operate the furnace without a filter.

As far as multimeter, I have one like this.
You would set the dial to ACV 200 to do the testing.
 
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Old 11-09-13, 01:23 PM
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Ok, measured with multimeter. When its on and running properly, reads 00.0, when it fails (and turned to on but not running), I am getting jumping values from 00.6 to 00.8 with occasional 01.1~01.3.
 
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Old 11-09-13, 01:52 PM
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A reading of 0.0 volts across the terminals when running would indicate the switch is closed. You can also test to see if you have 24V on each side of the pressure switch. To do this set meter to ACV 200 and when inductor motor is spinning, place the red lead from the meter on one of the terminals and the black lead to a chassis ground screw. Then do the same for the other terminal. You should get a reading of around 24V on each terminal.
 
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Old 11-09-13, 03:45 PM
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I get about 24.5 on both of them when furnace is running and functioning as intended.
 
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Old 11-09-13, 04:34 PM
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That would appear to eliminate the pressure switch as the issue but as you first stated it operates properly 9/10 times and if flicked corrects the problem. The only other test I can suggest is to jump the pressure switch leads. To do this remove the two wires from the pressure switch. Find a short piece of wire you can use to bridge the two wires you removed. A short piece of wire with alligator clips works the best for this but you can use a paper clip or other wire to make it work. Connect one end of the jumper wire to one of the wires you removed. Place the thermostat on heat and once the inducer motor starts to spin connect the free end of the jumper wire to the other pressure switch wire you removed. The two wires will then be jumpered together and the ignitor should activate. Since your furnace operates 9/10 times this still won't really prove the pressure switch is the culprit. An intermittent problem such as yours can be extremely difficult to diagnose.
 
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Old 11-09-13, 05:34 PM
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I was actually underestimating it by saying 9/10 times.. now that I have been actively trying to fix it I can say that it happens more often that that... if I turn on the furnace for a period of 4 hours at night, it will happen at lest once and often more.

so,

1) Turn on furnace it gets house to temp set and turns off
2) Temp falls below the set amount it starts again (here it will either fail to start or will start properly)
3) Once temp is reached it turns of again, rince and repeate steps 2-3.

How can it be anything else if tapping the pressure switch does the trick? Seems like it cant detect the pressure properly? It has a rubber diaphram inside right? being outside for 10 years maybe it dried out the rubber and so it has problems flexing? Im just guessing? also, i cant say for sure, but it seems that it does better during the day rather than at night (my thought is that temp is effecting the rubber piece?)

on the other note... should I not be getting 24ish volts on both leads even if the pressure switch is broken? Because when I measured it is working, so it would behave as if it wasnt broken?

like its faulty not necessarily broken....
 
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Old 11-10-13, 06:28 AM
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If it was my furnace I would replace the pressure switch. Being outside it is more susceptible to getting moisture into the diaphragm. I have seen similar intermittent problems caused by condensate drain issues and restrictions in the flue. Here is another test you can do on the pressure switch: remove the two wires from the pressure switch. Set your multimeter to the lowest ohms setting. Place the two leads on the pressure switch terminals. While the thermostat is calling for heat and the inducer motor spinning you should get continuity across the switches (a reading of 0 or something low like 0.1 or 0.2.
 
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Old 11-10-13, 03:22 PM
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So I took the pressure switch off (to see if I can take it apart maybe and see whats going on) but it looks like its made of molded plastic and there is no way to take it apart... so I did more cleaning, and blew compressed air into it to maybe clean out any gunk/dirt....

Used heater a few times since then (last night and this morning)... no problems yet...

i think you are right about it being hte pressure switch.

Thanks for all your help helping me figure this out... i am going to see if it breaks again, if it does I am going to try replacing the pressure switch...
 
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Old 11-10-13, 03:38 PM
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Yes, I truly believe it is the pressure switch since flicking it makes it start working. They don't fail that often but sometimes do.
 
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Old 11-12-13, 01:56 PM
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So its been 3 days... and ever sinec I blew into the pressure switch with compressed air the furnace seems to work fine... Ill give it at least a few more days, but so far so good.... weird.
 
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Old 11-12-13, 03:17 PM
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Sounds like you definitely identified the problem. You probably blew moisture out of the diaphragm or dislodged a tiny piece of debris to get it to work, at least temporarily.
 
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Old 11-12-13, 06:18 PM
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Having a pressure switch not consistently close may indicate that there's another problem.

Jumpering a pressure switch without confirming that there's a proper draft (measured pressure) is dangerous. Don't do it. Usually if a safety is open, there's a reason.

-------------
oh, BTW - that filter is actually is dirty even though it may not look bad. It's grey now; if you ever find it black, you've waited far too long.

The pleated ones are okay to use, but can really restrict airflow as they load up. If you don't have a/c, fiberglass is probably good enough.
 
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Old 11-22-13, 12:08 AM
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So its been almost 2 weeks, it has been cold and rained... heater has been used every day several times a day... ever since I blew compressed air into the pressure switch its been working perfectly... no issues at all!
 
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