Carrier 40YA-series air handler blower will not shut off


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Old 07-21-10, 12:06 PM
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Carrier 40YA-series air handler blower will not shut off

Hello,

Back at the beginning of summer, I had the original circuit board on my Carrier 40yr0336300 or 40ya-036-301 go out. I had my buddy who is a commercial HVAC guy (large scale stuff like chillers) come out and put in a replacement board, an ICM272C
like the one found here: ICM272C Control Board. The rewiring of the new board was done on a wire-per-wire basis with the only differences being where the 24V control voltage made it to the wiring terminals (as explained by ICM272C instruction page).

When the system came back up, no matter what we did, the fan blower would run continually:
  • Fan set to auto
  • Fan set to off
  • System set to cool
  • System set to heat
  • System set to off
  • Thermostat disconnected

Thinking it may have been the sequencer (SEQ2 as shown in below wiring diagram link), we replaced the old T-O-D H24V 15SH2 309573 with a White Rodgers variant; same result--the blower still blows constantly.

Since then, I have rewired a second, new ICM272C, thinking it may have been that the replacement was bad, yet the blower still blows continually.

We've been through the wiring diagram of the heater package as a whole, found here about 10 times to verify wiring: http://www.docs.hvacpartners.com/idc...lit/40y-1w.pdf page #7, figure #5.

I have tried replacing my digital thermostat with the original thermostat with no effect.

The issue seems to be somewhat related with the blue wire coming off of SEQ2, terminal 2 to pin #11 on the ICM272C. Insofar as when this wire is disconnected, the fan doesn't blow, however we don't get any control voltage, either.

Does anyone have any ideas? We've pretty much exhausted all of the standard ideas, outside of replacing the entire heater package and that's only because our local Aireco supplier can't find or cross reference a compatible replacement heater package since this one (either a 40YA900151 or 40YA900171) has been obsoleted by Carrier. To me, the only other option is the blower itself, but I'm probably off track on that one.

Any help would be most definitely appreciated!
 
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Old 07-21-10, 03:37 PM
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first of all, the info you want is not located page 7 figure 5. you want page 15 figure 13 cuz thats what page it says to go for a 40ya-036-301. it does seem that one wire or jumper needs to be placed in the wiring harness, however i dont think i can help just by looking at the diagram. but if you cant find it please dont replace the whole furnace, just install a relay that will shut the fan off whenever the system goes off.
 
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Old 07-22-10, 09:22 AM
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Hi ender2272,

Thanks for he response. You are correct in a way about the unit (what I'd call a chassis) being applicable on page 15, figure 13, however the heater package that's in there does not match that schematic. It's my guess the previous owners already had to change out the heater package once.

What's in there is a 15kW system and it matches the wiring diagram on page 7, figure 5 wire-for-wire the entire way through.

I also agree about not replacing the whole thing, but am afraid that's what most any company I call will tell me exactly that since the entire air handler has been obsoleted by Carrier for quite some time.

Lastly, the ICM272C has a fan relay on the board itself, which is why I've tried two ICM272Cs in an attempt to eliminate the board (and fan relay) as the culprit.

I've probably spent, over the past few months, 40 hours on this, some 10 of that with my friend who is a HVAC mechanic (albeit not on home systems) and it's truly perplexing why this issue can't be resolved.
 
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Old 07-22-10, 04:36 PM
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Did you check for shorts in the t-stat wire? Pulling the low voltage wires from the board (with the power off, of course) and seeing if the fan still runs would be the quickest way.
 
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Old 08-02-10, 12:06 PM
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Hi Jones1, et al.,

I had some time this weekend to sit down and diagnose the problem further and re-verify all the runs of the wire.

I was able to determine that there were no shorts in the t-stat wire either coming from the thermostat or the portion that goes to the outdoor unit.

What I did find is that when the blue wire that goes to the ICM272C, pin #11 is disconnected from the sequencer, the fan will begin to behave as normal on when the outdoor unit is running, off when it's not, and will obey on and auto from the t-stat.

Based on the diagram referenced below on page #7, figure #5, the blue wire from SEQ01 goes to pin #11 on the ICM272 which ultimately goes to EAC1.

Can someone tell me the implications of the EAC1 terminal? I can tell you that the cooling works fine, but am concerned that the heating may not work now.

FYI, I did call and pay someone $85.00 to come out and professionally look at the system--someone who said they loved this kind of challenge, but once they got in there, they basically wanted to install @ least a new air handler, but a whole system, which is pretty much what I expected.

Anyhow, any insight on the EAC1 terminal would be greatly appreciated.


Originally Posted by Jones1
Did you check for shorts in the t-stat wire? Pulling the low voltage wires from the board (with the power off, of course) and seeing if the fan still runs would be the quickest way.
 
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Old 08-02-10, 09:31 PM
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Do you have 24 volts to the sequencer?
 
 

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