Carrier Weathermaker 9200 - intermittent issues


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Old 12-16-13, 07:26 PM
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Carrier Weathermaker 9200 - intermittent issues

First time poster, long time lurker. I have a bit of a long story, so I hope you'll bear with me.

I have a 1999-vintage high-efficiency Carrier Weathermaker 9200 furnace (Model 58MXA080-12) that was installed when my home was built. It has been professionally maintained annually and has been very reliable. The only problem I've ever had with it was that the inducer assembly had a defect in the casing that was allowing water to run out the bottom. I had it replaced professionally about 4 years ago and it's been humming along ever since.

I am using a programmable Honeywell thermostat with this unit and I have it set to go down, during the day when I'm not generally home, to 65F. On the days that I allow it to do this, I come home to find that although the thermostat is calling for heat, the temps have only made it to about 68F and there's nothing coming out of the registers. This was never a problem until recently - and in fact, if I leave the thermostat set to a steady 72, everything is A-OK.

When it malfunctions, if I go down to the basement, I can hear an intermittent hum. The thermostat is set to "heat on". The status light is blinking steadily - no short or long flashes, but rhythmically blinking - which doesn't correspond to any known error code. The humming I hear is the inducer motor kicking on and off. It spools up, shuts down, rinse and repeat, in an un-ending fashion. The burner does not kick on, nor does the blower motor.

If I flip the switch on the side, the unit powers up and after a series of attempts to start, the burner will eventually kick on and is typically good for the rest of the night and until the next time I allow the temperature to dip. Occasionally, I have to reset it two or three times before it starts to run reliably.

I called in for service and of course, when the tech arrived, it was humming along without any issue. This particular tech was a bit of a waste of space - he didn't bother trying any routine maintenance. In fact, he barely touched the unit, aside from looking at the control board and saying that's the only possible thing that could cause the issue. He said he couldn't guarantee it would fix the problem, but asked me if I wanted to replace it proactively. I said I didn't and he left me with an $85 diagnostic fee... which is ridiculous as he didn't do any diagnosis at all.... but I digress.

So now, I'm taking matters into my own hands. Though I've never worked on HVAC, I am an old hand with electronics and work as a systems engineer, so I'm not intimidated by anything mechanical or electronic. I've removed the control board - it's solid state and I can't find any signs of failure - no cold solder joints or anything like that.

The ignitor is in good shape with no obvious signs of failure. I have removed the flame sensor and gently cleaned it with a bit of emory cloth. I've also sprayed out the burner with some compressed air to make sure it was all clean. I've checked all contacts (there are many spade-style connectors all over the unit and I've checked every one).

I also checked the intake and exhaust pipes - I see nothing obvious there - though I am concerned that the 2" PVC pipes do not have any mesh or screening on them to keep out the critters... and I do live in a wooded, semi-rural area. I have considered running a pipe snake through both pipes, just to be sure they're clear, though I haven't gotten around to it yet. I do intend to use some kind of chicken wire to protect the pipes at some point in the future.

I am tempted to try to clean out the drip lines on the inducer to see if there's any build up, but I'm not sure if that's a common problem and whether it's worth trying. The only codes the system has actually ever shown are 11 and 12 - which are just "no stored codes" and "begin blower motor cycle", respectively. Any tips or advice on where to troubleshoot next?

Thanks in advance - I would be grateful for any wisdom you might be willing to share.

-Chris
 
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Old 12-17-13, 05:45 AM
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Last night, I pulled the drain lines from the inducer and checked them for sediment / mold and other build-up. They were surprisingly clean. I think my next step is to find a way to scope out the intake/exhaust lines for any critters or debris. Not sure how to do that just yet... I wish I had something like a chimney inspection camera, but I don't seem to be able to find one at a rental company.
 
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Old 12-18-13, 03:17 PM
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Bump. Anybody? Despite checking all maintenance items, this issue persists.

Anyone think it's worth changing the control board?
 
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Old 01-07-14, 06:07 AM
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Fixed!

For anyone who stumbles upon this thread, I finally fixed my issue.

I replaced the hot surface ignitor, the flame sensor and the flame roll-out switch, all to no avail... though they were fairly cheap parts, so not a big deal.

Ultimately, I ended up replacing the furnace control board. Mine had P/N HK42FZ011 originally. Evidently, Carrier has decomissioned this style of board altogether - they had a number of earlier revisions which all had issues. The replacement part is 325878-751, or HK42FZ034. It differs significantly from the original in terms of the way it looks - it does not have a plastic outer casing and the wiring is significantly different, but it does come with harnesses for the major connectors to ease the installation process.

That said, I did run into a snag installing it and from what I've seen elsewhere on the Internet, I'm not the only one.

There were a number of white wires which had labels on the old board that didn't match up with the labels on the new board. All of these white wires are neutrals and connect to the neutral wiring block on the new board. There are a total of six spade connectors at this location, though two of them have alternate labels - EAC-2 is intended to be used for an air cleaner or humidifier (my furnace doesn't have one). There's another that is labeled with a black "BLW" label, which means "blower". The white wire that connects to "COM" on the older board is likely your blower neutral - that should connect to "BLW" on the new board. The other two white wires you have left over can be connected at any of the other neutral connectors, though I would recommend leaving EAC-2 open if you don't have an air cleaner/humidifier.

Got the board installed just after midnight last night and the furnace has been running perfectly ever since. Prior to that, it had to be reset every 2 hours or so to keep it heating the house. I have not been through a programmed low-temp, back to normal situation yet - though when I first powered it on following install, the house had dipped into the 60's and the furnace brought it back up to 72 without issue, so I do believe this did the trick.

One more item of note - P/N 325878-751 has an aftermarket alternative made by ICM. From what I've read, Carrier has some proprietary safety mechanisms built into the logic of their OEM board. Additionally, the ICM board supposedly doesn't have the adjustable blower off delay, nor does it account for different furnace types. Though the ICM board is significantly less expensive (I found the OEM board for about $220 shipped, but the ICM generally goes for about $120-150), I found several reviews where it had actually caused significant problems over the long run. I highly recommend sticking with the OEM board... just make sure the seller actually sells you the real deal. If you find it for less than $200, you're probably not getting an OEM board.

Hope this helps someone down the road.
 
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Old 01-13-14, 03:04 PM
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My Carrier 9200 is making a groaning noise when it is calling for heat. It is the combustion blower, not the main blower that serves the house. Is this unit intended to be oiled/greased, however I cannot find anything that indicates that it is? It sounds to me like the bearings are worn. Does this make sense for a 15 year old unit? If yes, are there places to buy replacement blowers for this unit on-line?
 
 

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