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Old 01-17-2012, 10:55 PM   #16
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New control board or fix it?


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Originally Posted by Bobeht View Post
I'm assuming I need a new control board for this furnace. Maybe it can simply be repaired or isn't even the problem in the first place.

Carrier Weathermaker 9200 58MXA
Part # on current control board is HK42FZ016
I'm thinking of getting the ICM282 as a replacement. Working on small electronics doesn't bother me so if this cheaper board does the job once it is installed I'm not paying OEM prices just so it looks the same.

Here's my problem though. (this furnace has been running fine for 10 years) The induction fan comes on, the fire starts, no error codes are flashed but the instant the blower comes on the flame goes out. The blower runs for a minute while it flashes the code 12 (one short two long) and then shuts off. Code 12 just says the blower is running for 90 seconds after a call for heat (R-W closed). What is "R-W closed" anyway, maybe this is my problem? Ten minutes later it cycles through this again and it never ends. Flame sensor looks basically new. I cleaned it a touch with some 1200 grit sand paper but that was purely cosmetic I think. If I leave it disconnected I get error codes so I'm assuming it works.

The trouble shooting guide leads me to checking the DC microamps on the flame sensor wire. This guide is confused though because it first says "Is the DC microamps below 0.5?" and then in the very next troubleshooting bubble is says the "current is nominally 4.0 to 6.0 microamps". So which is it, 0.5 or 5.0? Doesn't really matter though because my amp meter is a Fluke t5-600 and won't measure these small amps anyway. So as I mentioned I'm assuming the flame control sensor is working and it's a problem in the control board.

Can I fiddle with some jumper settings on this board and get it to work? Clean it maybe? I don't know, I'm grasping at anything that isn't a $200 plus OEM board.

Thanks in advance for any useful information about this. I hope I've explained it well enough.
I didn't think any of them old boards was still around, carrier had a voluntary recall on those boards, way back when........the resistors on the board (a pair of them) was mounted to close to the board, they were getting so hot the they would melt the solider and cause an erroneous fault code. back then the repair was 100% covered by carrier corp. now its out of your pocket....i am sorry. But yes you need a new board.

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Old 01-18-2012, 02:35 AM   #17
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New control board or fix it?


It's down right silly I say. I've given up on what makes sense and am going with what works. The board calls for a 3 amp fuse and its only purpose really is to do just what it did, pop when a numskull grounds it while it is still powered up. I've hooked everything back up the way it was before any trouble started with my two modifications, the 5 amp fuse which has no bearing on my original problems and the speaker wire now hooked up along side the thermostat wires. The stat seems to be a closed circuit enough to get the cycle started but when the amps go up or volts draw down or whatever when the blower comes on this circuit reads as open. The control board is doing just as it is asked. Maybe tomorrow I'll check the ohm level on the thermostat line from the furnace to the thermostat. Doesn't make sense but with my speaker wire jumped out every thing works fine. My plan now is to jump up to the 20th century and get a stat that runs the fan only option as well.

I've seen stranger things in the alarm sensor industry. Put the wrong ohm resistor by just a little bit in the sensor and the line running to it can do some weird things to the brain box of the alarm. It doesn't take much of a resistance change to alter the brain box into thinking it's not there or has been tampered with.
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Old 01-18-2012, 12:05 PM   #18
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New control board or fix it?


Stranger than fiction but I have a feeling that albeit it is working now it's only a matter of time. With low voltage lost while on call for heat, R-W closed, the blower should not ever go into 90 second blower on time delay. That is simply like turning the stat off while the system is heating or turning the temperature set point up, stopping the call for heat. The blower on time delay happens only when the high voltage is lost (at the control board) so this problem is nothing to do with you bypassing the stat, it has to do with the control board itself.

You said that you blew out the board, might have blown some dust off of it which was interfering with power or you could have possibly moved a resistor with a weak connection back into place and now the board is acting normal but again, I have a feeling it's just a matter of time.

Let us know if and when that time occurs.
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Old 01-18-2012, 12:54 PM   #19
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New control board or fix it?


some times we get posters who just want play "Stump The Staff". Ain't saying this is one...but I will leave that up to the reader to decide.

I have to wonder how long an op will let his furnace go as the temp drops in the house and banters a technical staff.
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Old 01-18-2012, 03:10 PM   #20
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New control board or fix it?


This is no stump the staff deal, I assure you. Let me clear some issues up here though. Imagine a 30x60 foot garage/wood shop with 14 foot ceiling space to the rafter/floorboards of the apartment above it about 30x45. The garage space has its own furnace hanging from the ceiling blowing hot air right out of it to warm this space, actually it's quite toasty in there. So above in the apartment it can't really get that miserable. Even just circulating air the broken furnace picks up some heat from the garage below, all the duct work is in the garage. Uncomfortable in your shorts yes, but not that bad compared to being stuck in a snowbank in a ditch or something. (I once lived 8 miles south of the Canadian boarder so I know cold.) There' an electric portable heater keeping the chill off in the apartment but this isn't a long term economically sound idea. Especially when there's a perfectly good furnace right here that's almost installed correctly. It was all installed by a construction lacky, not an HVAC guy. I'm here 10 years after the fact trying to fix it. I've not even gone into all of it, just the parts I need help with. I don't want to confuse you all with extraneous information, but it had 2" pipe ran for the inlet and outlet air. Not just that but at the length it was ran and the unnecessary number of 90 degree bends it took it was never totally healthy. And most of that was run outside of the insulated heated part so it had no chance to work right really. Moisture would freeze up in the outlet pipe and plug it with ice, then the furnace wouldn't run because it couldn't breath. This only ever happened if it dropped below about -10 but that happens here a couple times a year. I've already ran some 3" stuff with only 4 total bends at about 18 feet instead of the roughly 30 feet of 2" stuff. See, all this is muddling this issue. Hence the reason I left it out. I fixed it already. As to my issue now, it's like this. The stat can begin the cycle but if I don't jump out my speaker wire before the blower comes on it shuts down like the stat has warmed up and opened the circuit. On the previous page I asked about "R-W closed" and Doc explained it. Now this is just me but he explained it a little ... off I guess. I'll explain from my perspective and you can see if we're talking about the same thing. Probably are. R and W are just the red and white wires that go to the stat. From Doc's explanation earlier about what each wire does if I have a stat that does cooling and fan also then I'd use the Y yellow and G green wires. The R and W are simply the stat's contact point and the temp sensitive spring opens and closes the circuit. Doc said "With low voltage lost while on call for heat, R-W closed, the blower should not ever go into 90 second blower on time delay". I'm confused as to what that even means. When R and W are closed it's a closed circuit and the furnace runs. When that circuit opens the furnace shuts down. The furnace shuts down by first shutting off the fire in the heat exchanger while it continues to run air for an additional 90 seconds. It does this every time it shuts down correctly, i.e. the temperature warms up the thermostat and the contact breaks opening the R-W circuit. If it didn't it would leave heat in the unit instead of blowing it out, maybe even damaging it by shutting it down too abruptly. The same reason the induction fan continues to run for a few seconds once the fire is out, to clear the outlet pipe of the moisture in it. I'll come back with a final update once I buy and install a modern thermostat, if anyone cares.
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Old 01-18-2012, 03:11 PM   #21
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Where did my spaces go?!! I had paragraphs and everything! grrrrr
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Old 01-18-2012, 03:30 PM   #22
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New control board or fix it?


Quote:
I'll explain from my perspective and you can see if we're talking about the same thing. Probably are. R and W are just the red and white wires that go to the stat. From Doc's explanation earlier about what each wire does if I have a stat that does cooling and fan also then I'd use the Y yellow and G green wires. The R and W are simply the stat's contact point and the temp sensitive spring opens and closes the circuit. Doc said "With low voltage lost while on call for heat, R-W closed, the blower should not ever go into 90 second blower on time delay". I'm confused as to what that even means. When R and W are closed it's a closed circuit and the furnace runs. When that circuit opens the furnace shuts down. The furnace shuts down by first shutting off the fire in the heat exchanger while it continues to run air for an additional 90 seconds. It does this every time it shuts down correctly, i.e. the temperature warms up the thermostat and the contact breaks opening the R-W circuit. If it didn't it would leave heat in the unit instead of blowing it out, maybe even damaging it by shutting it down too abruptly. The same reason the induction fan continues to run for a few seconds once the fire is out, to clear the outlet pipe of the moisture in it. I'll come back with a final update once I buy and install a modern thermostat, if anyone cares.
Bobeht,

you absolutely 100% correct. R and W are the "heating terminals". All the other terminals are convenience terminals for A/C and Fan On operations. I am replying to your original post and problem....
Quote:
The induction fan comes on, the fire starts, no error codes are flashed but the instant the blower comes on the flame goes out. The blower runs for a minute while it flashes the code 12 (one short two long) and then shuts off. Code 12 just says the blower is running for 90 seconds after a call for heat
as i stated in post # 16

I have seen this many times.....its a sign of a bad board, from way back when.......bad resistor mounts on a board. I think you may have been mis-guided and maybe not............but i am sure that you need a board still.
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Old 01-18-2012, 03:32 PM   #23
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New control board or fix it?


DoOd!!!!! I misunderstoOd your definition. You are talking about blower OFF time delay and yes, most if not all gas furnaces do this after a call for heat has been terminated such in set point of stat being reached. The gas valve closes, flames shut off and the blower remains on for a time to remove and make the most of any residual heat. That is normal.

I was thinking it was blower ON 90 seconds which if you go and cut the breaker to the furnace off, turning off the high voltage to the furance and then turn it back on and ONLY on Carrier furnaces, the blower comes on for 90 seconds regardless and then you can control it be it heating or cooling or fan on only.

Whoopsie!!

Yes, your stat is the issue and yes, you can purchase an up to date stat and IF YOU HAVE AN EVAPORATOR COIL AND A CONDENSING UNIT ALL HOOKED UP AND READY TO GO you can and will have cooling, with the use of the Y terminal from the furnace to the stat and the common from the condenser to the common on the control board of the furnace as well as the cool wire from the condenser to the Y terminal of the control board so two wires on the control board Y and one on C. If not all you will be able to solitify on top of your heating is the use of the G terminal, fan on.
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Old 01-18-2012, 03:34 PM   #24
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heat antisipator? if so why would it flash a code?.....courious
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Old 01-18-2012, 03:34 PM   #25
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Where did my spaces go?!! I had paragraphs and everything! grrrrr

<snicker>
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Old 01-18-2012, 03:57 PM   #26
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New control board or fix it?


Yes, the flash code 12, forgot all about that. Would mean that the board itself has lost HIGH voltage, not low voltage.

Something is still very fishy.
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Old 01-18-2012, 04:03 PM   #27
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New control board or fix it?


Not so long ago this furnace was a big scary fire breathing monster in a corner closet with tentacles reaching out to everywhere in the building. Now that I've spent some quality time getting to know it, it's nothing but a metal box with a couple of motors and a gas valve. I've stood over it Captain Morgan style with my leg propped up on it looking all triumphant. (At least in my mind anyway) Thanks to Doc and hvac5646 and biggles for the help getting me there. You are my Huckleberry!

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