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Old 07-30-2012, 11:56 AM   #1
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Carrier 9200 problem


I am new to this forum, but have spent alot of time trying to figure out this problem.

Carrier 9200 with A/C unit located outside. System was dormant for about 10 months. First turned it on about 3 weeks ago, to use the A/C. System started, got A/C and fan. Ran about 15 minutes then quit. Thermostat (carrier, 24vac powered) began to wink out, going out completely.

I turned off the power and checked breakers and fuses. 9200 breaker OK, A/C breaker OK. Checked A/C fuses at unit: OK. Checked 3A fuse on controller board: good. Controller board gives constant yellow LED indicating good operation.

Going to the A/C unit, I can push the contactor in manually, and the compressor and fan start.

When I replaced the thermostat with a Honeywell battery unit, and can hear the relays clicking in for the various modes. Using this, I find the following:

1. fan won't come on.
2. furnace won't come on.
3. A/C won't come on.

When I measure for 24vac at the terminals on the PCB, I see the 24VAC between commond and red. When calling for any (fan,heat,A/C), I see about 1.6VAC. Yet, the PCB stays powered up, and yellow LED is on.

When I short the test jumper (TWin, as I recall) to common, PCB goes into system test mode, and inducer fan comes on, blower comes on and ignitor comes on. Unit will flash 1, 1 when this mode comes up. Does not indicate a problem.

So, first, I am thinking, well, the 24VAC xformer went bad, right? Because the voltages at the G/Y/R/W terminals on the PCB drop as though something is shorted, but the board keeps on running.

What is up with this? It seems like something really quite simple (diag mode runs most everything else, and I can push A/C contactor in and get that unit to go).

Thanks!

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Old 07-30-2012, 01:55 PM   #2
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Carrier 9200 problem


Wiring of the old stat and wiring on the new the same? Got pics?

It's not the board or the transformer if the board is consistently giving you a normal operation code. It wouldn't do that if the transformer was shot.

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Old 07-30-2012, 02:41 PM   #3
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Carrier 9200 problem


Doc:

Reasonable question.

I don't have pics, but can tell you the following: I use this same Honeywell Tstat in my home, and know how it works. That said, I did the usual thing: where the wire went to a color code on the Carrier tstat, I routed that wire to the same color code input on the Honeywell. R->R, W->W, G->, Y->Y. I did not connect the blue wire, as that one isn't needed on a battery powered tstat.

But here's the thing: when I put the Carrier Tstat back in (after having been out of the circuit, without power for a few days), it seems to clear itself of the last setpoint and mode and so on. And, it comes to life: I can see the display nice and plain. If I now call for heat, as soon as I set a setpoint that crosses the current temperature (for heat), the display instantly goes blank. This is also when I can measure the 1.6v at the terminals on the board in the 9200.

The original Carrier tstat, I don't think, was miswired or is otherwise shorting anywhere: I am following the wiring from the living room all the way down to the furnace, and out from the furnace to the A/C unit.

Moreover, independing of the tstat (make and model), I _should_ simply have to jumper from Red to Yellow to cause the A/C to come on, or jumper from green to red to have the fan come on, or jumper from white to red to have the furnace come on.

No joy in any of those cases. Reads 1.6v at the 9200 PCB terminals.

All the while, the PCB shows 26.6v at these terminals (common and red), and the yellow led is continuous on.

This is why I am puzzled; a straight jumper will not produce component turn on, yet, much of this will turn on when I trigger the diagnostic mode. If that PCB wasn't also powered by the same 26v xformer, I'd say the xformer is shot.

But there I am: a contradictory set of observations, and no working furnace or A/C, yet, passes diagnostics!

I am about to bypass the whole mess and drive direct; it is simply not making any sense to me.

Is this making any sense to any of you?

-M
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Old 07-30-2012, 02:47 PM   #4
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Carrier 9200 problem


Not color coded, just so happens on your stats to work out that way.


Stat terminals:
R-24 volts (provided from furnace control board)
G- Fan
Y-Cool
W-Heat

Did your old stat have the common hooked up? Is the common hooked up in the furnace?

Did you try jumping at the control board, r to y for cool or r-g for fan? Turn the stat into the off position and jump controls at the control board.
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Old 07-30-2012, 02:54 PM   #5
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Carrier 9200 problem


Doc:

Yes, I have been following the same color code you indicated for the various functions:

R- 24v
G- fan
Y - A/C
W - heat

I am sure the common is on the terminal strip at the PCB in the furnace; it is NOT being brought out to the Tstat, that much I know for sure.

I will disconnect the tstat from the wall plate, and then do the jumpers directly on the terminal strip that is on the PCB.

You are clearly thinking that the tstat is the problem, it seems.

Thanks,

M
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Old 07-30-2012, 03:03 PM   #6
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Carrier 9200 problem


I'm thinking your wiring is the problem. The stat is merely a switch, directing control voltage back to the control board which in turn controls the system. You don't have to remove the stat from the wall. All you need to do is remove the wire from the R terminal to the stat and then jump at the board. By removing the power to the stat it is out of circuit completely. I'd also remove the common if there is one going down to the stat which is still hooked up at the control board just to be safe. If you remove the r and the C to the stat at the control board make sure it's the common to the stat and not the common to the outside condenser if indeed there are two. Without a common to the condenser the outside unit will never come on and that common is hooked at the C on the control board as well. In other words, if there are two wires on the common on the board, one is going outside (with at least one other wire) and then the other will be going to the stat if it's there.

Or simply connect that common in the stat and then try the stat. Simple.
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Old 08-01-2012, 11:09 AM   #7
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Carrier 9200 problem


This is in my daughter's new house, and I can get over there only periodically.

However, last night, I confirmed the following:

1. The common is a blue wire, and does come up the Carrier tstat on the livingroom wall.

2. When I disconnected the tstat from the wall mounted plate, I was able to do the following:

I made a jumper, connected to the R terminal on the furnace controller PCB, and then jumped as follows:

R->G : blower comes on.
R->W : furnace comes on.
R->Y : A/C comes on.

I did this while keeping the tstat wiring in place on these terminals (although the tstat had been removed from the wall plate before I did this).

So, all elements appear to function. This would indicate to me that the original problem, in which the system was set to call for cooling, with the A/C coming on, and which quit about 15 minutes later, with the tstat display winking out, is really caused by a failure of the tstat itself.

I have a new honeywell tstat, and I'd like to use this in its place. The thing is, I have wired it pretty much straight up:

Y-> Y
G-> G
W-> W
R-> R (this one has R jumpered to RC on the mounting plate).

I left the Blue wire off this tstat, as the manual indicates not to hook this one up if it is the common.

In this configuration, I can't get any of the furnace functions to come on (although I can hear the relays clicking when, say, I am calling for heat, and the setpoint goes above the room temperature).

I suppose it's possible that I have a bad tstat right out of the package, I am not sure.

Thanks,

M
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Old 08-01-2012, 12:33 PM   #8
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Carrier 9200 problem


Disconnect the common at the control board or hook up the common at the stat.
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Old 08-01-2012, 12:54 PM   #9
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Carrier 9200 problem


Dear all
Please help me. My Computer not run properly.
some error message.

Thanks
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Old 08-10-2012, 10:43 AM   #10
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Carrier 9200 problem


After a great deal of screwing around, I found the problem. Furnace and A/C had been installed with a Little Giant pump to push collected condensate to a remote drain. This pump has a float operated switch, which worked fine. It also has a float safety switch, which had been wired in series with the Red terminal of the furnance PCB. The safety switch was bad- seriously intermittent with varying contact resistance. This explained why the tstat was flickering and going dead altogether, and why a replacement tstat did not work, either.

I don't quite understand why this was wired in series with the Red line; I would have wired it in series with the Yellow. After all, if the condensate pump fails, you want the A/C to shut off, right? Not the whole system.

Anyway, bypassing the safety switch (pump operates just fine off its float switch; it is the safety switch that's bad, here) all is good. Getting replacement switch.

Thanks for the help!
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Old 08-10-2012, 01:31 PM   #11
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Carrier 9200 problem


if it is a 90% furnace which makes water in the winter you would want the R wire to be opened by the secondary float.
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Old 08-10-2012, 01:37 PM   #12
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Carrier 9200 problem


Thanks for that- it IS a 90% furnace, and I did not know this would make water during use for heating. Good to know; I now understand why that safety switch was wired in the way it is, and I won't change that. Just will replace the faulty switch.

Excellent help from this site! Greatly appreciated.
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Old 08-10-2012, 08:27 PM   #13
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Carrier 9200 problem


I never break the red of a gas furnace, just the yellow. A condensate over flow from it is less costly and time consuming then a water line freezing and breaking in the winter.
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Old 08-10-2012, 08:32 PM   #14
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Quote:
Originally Posted by beenthere View Post
I never break the red of a gas furnace, just the yellow. A condensate over flow from it is less costly and time consuming then a water line freezing and breaking in the winter.
guess that depends on where you live and if furnace is above or on a conditioned space. We get cold here but pipes rairly freeze and break here. every once and a while we get those winters. See alot more pumps fail and damage floors.

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