Carrier Weathermaker 8000 mid-efficiency 58WAV upflow loss of flame

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  #41  
Old 02-13-15, 01:48 PM
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The inducer does not continue, it quits after the flame drops out, and only restarts with the new ignition sequence.
 
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  #42  
Old 02-13-15, 03:16 PM
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Is the inducer supposed to keep running?
 
  #43  
Old 02-13-15, 03:31 PM
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Houston, I think Jackson stated the flame & inducer drop out before there is 24v ac across the pressure switch. I'm starting to wonder if there is an auto reset limit opening.

Jackson, How soon after the burners go out can you recycle the furnace?
 
  #44  
Old 02-13-15, 04:26 PM
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Grady,
The furnace begins recycling immediately, as soon as the main blower finishes a 90 second run after the flame drops out.

You are correct about the flame and inducer dropping out first.

An auto reset? I know there is a manual reset limit. Where might the auto reset be hiding?

Sorry, let me amend that: on this furnace the hi-limit is auto reset; the draft and roll-out are manual resets.

I've had leads on the hi-limit before when the flame drops out and never seen it open; could it be happening so fast that my cheap tester won't read it?

The hi-limit has never been replaced.
 
  #45  
Old 02-13-15, 05:12 PM
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I certainly would not expect an auto reset limit to recycle faster than your meter can read.

Something I did find while reading a manual on your furnace is the inducer is supposed to run (recieving 120v) for 5 seconds after the stat is satisfied & the flame goes off.
 
  #46  
Old 02-13-15, 07:21 PM
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I set the thermostat for a 1 F rise, so the furnace would make the temperature and shut down normally, which it did.

The inducer does keep spinning after the flame, although it's hard to tell if it's because it's energized, or due to momentum.

If you could advise me how to check for 120V at the inducer, I'd appreciate it.

Thanks
 

Last edited by jackson4015; 02-13-15 at 09:54 PM.
  #47  
Old 02-13-15, 10:42 PM
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I don't know if you can get a meter probe into the plug(?) marked PL3 or not but if you can, when the inducer is energized you should get 120v between black & white. Maybe you can measure at PL2 to a neutral. Again you are looking for 120v.
 
  #48  
Old 02-14-15, 01:51 AM
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The easiest method to check if your inducer is still getting power for a few seconds after the flame drops out due to pressure switch tripping is with a non contact volt stick, or a clamp on amp meter.
 
  #49  
Old 02-14-15, 11:02 AM
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Many thanks for your combined help Houston and Grady.

I've done what I can with my limited resources and experience and am appreciative of your efforts on my behalf. I was truly hopeful I could have resolved this problem especially considering the expert advice I received from you both.

It's frustrating for me because I doubt I've relayed the symptoms as clearly or as accurately as you require. If the two of you were here, I'm sure the furnace would have been diagnosed efficiently and the issue resolved.

Houston, I have your list of checks that should be undertaken by a competent technician. Hopefully I will find one, I'm just not sure how to go about that.

I'll keep monitoring this thread in case either of you have additional information.

Take care.
 
  #50  
Old 02-14-15, 02:08 PM
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A manometer, an clamp on amp meter, and a non contact volt stick would be of assistance in checking this furnace.
 
  #51  
Old 02-16-15, 08:59 PM
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gas valve?

Houston and Grady, hopefully you're both still monitoring this thread.

I'd like to address the possibility of the gas valve failing.

I didn't mention this in my original post, but this condition has been ongoing for a couple of years, with lengthy periods when the furnace would satisfy the thermostat.

When this first started, the furnace would get to near the thermostat setting before the flame would drop out. Later, it would happen earlier in the cycle, until now when the burners stay lit for only a few minutes.

The condition has deteriorated to the point it is at now, about 8 minutes of flame on the first attempt, and even that seems to be decreasing.

Most times the flame dropping out is accompanied by a knocking or clunking sound that I'm pretty sure is coming from the gas valve.

The furnace is 22 years old.

Could the gas valve be failing to the point now where it can't maintain gas flow to the burners?

It has been bitterly cold here lately, and I have read that as the temperature drops, so does gas pressure.

If the gas valve is already weak, could the intense cold be making it worse?

Grady, you suggested earlier in this thread that because my tester showed the pressure switch opening after the flame drops out, that this might not be a draft issue as the code 31 would suggest.

Please let me know what you think of this scenario.
 
  #52  
Old 02-17-15, 01:54 PM
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The gas valve is electrically operated. Unless there is a low gas pressure cut-off switch, I wouldn't think temperature/pressure would have any effect.
The more I think of this, the more I think it is a limit opening, but I've been wrong before.
 
  #53  
Old 02-18-15, 09:32 AM
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Hi Grady,

It really does seem to be going out on limit, just by the nature of the shutdowns.

I've checked the high limit. The flame roll-out and draft limits are both manual reset and haven't tripped.

The one check I haven't been able to do is the vacuum at the pressure switch.

I have a call in for the furnace tech and will have him put a manometer on that switch.

The last time he was here he did disconnect the pressure switch leads and bypassed the switch by holding them together, I'm not sure at what point during the cycle, but this didn't keep the furnace running.

If the pressure is wavering near the break point of the switch, the manometer test is essential to prove whether or not the inducer is doing its job, correct?
 
  #54  
Old 02-18-15, 10:58 AM
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I have a call in for the furnace tech and will have him put a manometer on that switch.
Make sure he installs it with a tee.

The last time he was here he did disconnect the pressure switch leads and bypassed the switch by holding them together
If he bypassed the pressure switch & the furnace did not keep running, in my mind that takes pressure related issues out of the picture but just holding the wire ends together is not a very good way to test. A jumper wire should be used. If I recall correctly, the only thing left is temperature according to the key for a code 31.
 
  #55  
Old 02-18-15, 02:27 PM
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13 and 31 are easily confused when counting flashes.
13 is a limit and 31 is a pressure switch.
 
  #56  
Old 02-18-15, 06:48 PM
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It's definitely 3 short, 1 long Houston.

The troubleshooting you and Grady have given points to the manometer teed into the pressure switch as a key test. I'll make sure this happens.
 
  #57  
Old 02-18-15, 07:52 PM
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Grady, just so I know for reference, how do you jumper the pressure switch properly? I didn't think it was possible to bypass the switch without interrupting the cycle. As I understand it, you would jumper it after it had closed, but wouldn't attempting to jumper the switch immediately tell the board something was amiss?
 
  #58  
Old 02-18-15, 07:57 PM
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You have to disconnect the wires, create a call for heat, & within a second or two install a jumper between the wires. Obviously this is for testing ONLY.
 
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Old 02-18-15, 08:12 PM
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Thanks.

I understand your caution about testing purposes only. Noted.
 
  #60  
Old 02-19-15, 08:59 AM
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You would need to give the board an open circuit when the inducer is not running but give it a closed circuit after the inducer starts if you wanted to jumper the pressure switch wires.


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It would probably vary with different manometers but I use a 3/16" x 3/16" by 1/8" Tee to connect my manometers to a pressure switch. I also use 1 or 2 small pieces of tubing since the furnace tubing would kink in many cases.
 
  #61  
Old 03-01-15, 07:58 PM
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Hi Houston or Grady,

Would the inducer motor on this type of furnace have a thermal overload built in?

If it does, and is shutting itself down, could this be a reason why the pressure switch would open after the inducer shut down?
 
  #62  
Old 03-02-15, 05:06 AM
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This would be tough to prove without the meter setup that I pictured.
 
  #63  
Old 03-02-15, 09:38 AM
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I've got a furnace tech coming sometime in the next few days to try a new inducer assembly- he's pretty sure the inducer is slowing down. That's why I was asking about the thermal overload possibility.

The inducer is rated for 1.8 amps, but is pulling 2.0 from his test, and he said the motor was getting too hot for the short amount of time it was able to run- about 5 minutes.

He removed the entire assembly to take a closer look. He thought it was significant that the blower wheel was cooler than the motor housing.

He did tee in his manometer with the pressure switch while the furnace was running. It read 0.6".

I didn't realize until later that he hadn't taken a manometer reading when the flame dropped out. I thought I would ask him to do this before he tried the new inducer.

What do you think?
 
  #64  
Old 03-02-15, 11:25 AM
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A voltage measurement to the inducer when it drops out would be the test to condemn or pass the inducer.
 
  #65  
Old 03-02-15, 03:06 PM
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If the inducer was slowing down and then dropping out, what sort of voltage reading would you expect to see from the inducer?

I do remember watching the tech probing the inducer with a volt stick while it was running and getting a solid light, but as soon as it dropped out the light became intermittent and wouldn't return to solid, which seemed to puzzle him.

Could you explain to me how to test the voltage with my multi-tester (ie. where to position the probes and when)?
 
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Old 03-02-15, 04:48 PM
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Can you get a reading at the inducer?
Do the harness connections to the inducer look corroded white or green?
I would expect to see 2 connections between the board and the inducer. I would have a look at both.
 
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Old 03-02-15, 05:16 PM
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Unless the tech's meter was a really good one, I don't think the 0.2 amps is significant.

If the wires are long enough, you may have to cut, strip, & splice with wire nuts in order to give you a place to probe with your multimeter.

If the motor was overheating & going off on overload, there would still be voltage present. The source of voltage should be the board.
 
  #68  
Old 03-02-15, 05:18 PM
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There is no corrosion at the inducer.

I'm not sure how to make the reading at the inducer. Would I probe one side of the inducer and connect the other lead to ground? ( pull the connectors out just enough to probe with the leads)

I've been led to believe there is no thermal overload protection on this inducer motor. If there is, and it is shutting down on overload, wouldn't this happen without any input from the board or the pressure switch?
 
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Old 03-02-15, 06:10 PM
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The overlaod would be internal to the inducer motor & would not require any action from the board or pressure switch.

To check incoming voltage to the inducer, put one probe on each motor lead connection (I doubt you can get to them) & look for 120 volts.
 
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Old 03-02-15, 06:51 PM
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I can get to them, but the connectors are plastic covered. If I pull them back enough to expose the spades but still leave them connected, would it be ok to put the leads on the spades?

If I lose 120 V when the inducer quits, what does that tell me?
 
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Old 03-02-15, 07:18 PM
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If I pull them back enough to expose the spades but still leave them connected, would it be ok to put the leads on the spades?
That is what I have done.

If I lose 120 V when the inducer quits, what does that tell me?
It would tell you the inducer is ok.


Do these 2 wires look ok at the edge pin connector to the control board?
 
  #72  
Old 03-02-15, 07:28 PM
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Thanks Houston, I'll give it a try.

I'll try to get a look at the wires at the connector.
 
  #73  
Old 03-02-15, 07:46 PM
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Here's what happens:

The flame drops out and five seconds later I lose the 120 V at the inducer, but for those 5 seconds I'm pretty sure the inducer is free-wheeling and not under power.
 

Last edited by jackson4015; 03-02-15 at 08:19 PM.
  #74  
Old 03-02-15, 08:35 PM
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Here is what I think is happening:

According to the sequence of operation from the install manual, the inducer is supposed to run a 5 sec. post purge after flame and then stop. It has always done this, even when the flame has dropped out early.

According to the troubleshooting guide for this furnace, it is only a problem if the inducer keeps running beyond the 5 sec. post purge.

But until I tested for voltage at the inducer, I could never tell if the inducer was powered during the 5 sec. post purge period.

It is in fact receiving 120 V for 5 seconds after the flame, but I'm almost positive the inducer is only free-wheeling for that five seconds, at which point the 120 V is stopped, as it is supposed to.

The only conclusion I can come to is that the inducer is cutting out on its own, which keeps re-initiating the recycling of the furnace.

The possibilities for a fault code 31 do include a "defective inducer motor", but it seems being able to nail it down to that through a standard sequential troubleshoot is difficult at best.

This probably is not a logical assessment of whatever is going on here, but let me know what you think.
 

Last edited by jackson4015; 03-02-15 at 09:03 PM.
  #75  
Old 03-02-15, 09:20 PM
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Now you are back to needing an amp meter.

Is it pulling amperage during the time in question?


Home Depot has this entry level clamp meter that will check amps.
http://www.homedepot.com/p/Klein-Too...L200/202521277

I own the Klein CL2300 the also checks flame sensors, amps DC, and Capacitance over 1000 microfarad but it runs quite a bit more.

I think that I prefer the $40 Uni-T over the $60 Klein clamp meter.
 
  #76  
Old 03-03-15, 05:53 AM
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Are you measuring across L1 and L2 to the inducer?

Measuring L1 to ground may not show you a faulty L2 connection at the edge pin connector.
 
  #77  
Old 03-10-15, 01:40 PM
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Hi Guys,

It turns out the inducer was the problem.

The tech ran 120 V direct to the inducer motor and about a minute and a half later it stopped dead.

He said he'd never seen one stop and then be able to restart over and over again.
Apparently that was making the diagnosis difficult, until he finally bypassed the control board and powered the motor directly, and we both saw it just quit.

As I understand this, a voltage check at the inducer when it dropped out should have been a solid indicator of a problem with the motor, but it was puzzling because the voltage was there for that 5 seconds after the inducer quit, and then there was none.

The new motor has been up and running for a week now.

Thanks to you both Houston and Grady, for helping me understand the workings of this furnace, and furnaces in general, and especially for guiding me through the troubleshooting process. I found that very interesting and informative, and helped me be able to have informed discussions with the tech.

Take care.
 

Last edited by jackson4015; 03-10-15 at 02:08 PM.
  #78  
Old 03-10-15, 06:32 PM
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Thanks for posting back with your solution. I am sure that it will help others with a similar problem in the future
 
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