American Standard control board flashing 3x

Slowhand63

I’m at a loss for words.  

Yesterday, I woke up with the pressure error and F2 not running.  After powering it down for a while, it started up and ran fine all day.  Tried installing a brand new inducer - immediately got the error code, so I put the old inducer back in. 

It ran fine overnight and all day today.  

Believing it was a control board issue, I replaced the board. With the old inducer in it ran fine. Powered it down, and installed the brand new inducer.  Immediately got an error. Reverted back to the old inducer and it’s running again.  

For good measure I pulled the white plastic collection box and flushed it. I also replaced the capacitor on the inducer because I had the capacitor and it was easy to do.  

So…. It’s not the control board. 

I also removed and snaked the tubing - inspected it best I could.  Is there any other way to check for air leaks (I don’t have a manometer). 

I think there’s a good chance either tomorrow or Thurs morning I’ll wake up to an error code.  Upon reset it will run fine all day. 

I’m considering swapping the inducers between F1 and F2 to see if the problem moves, or maybe swapping the tubing from one to the other.  

Thoughts?

Slowhand63

Took 2 minutes and swapped the tubing between F1 and F2.  This was the white tubing that ran to the pressure switch, and the black square tubing that runs from the combustion chamber (?) to the gas valve assembly to the pressure switch.  It was easy to do - let’s see if it makes a difference.  

In the event it’s a tubing issue (if only I was so lucky!) is there a spec sheet or ?  I can probably find a match for the white tubing at the local hardware store, but the black square tubing is pretty unique.  

EdTheHeaterMan

Black square tube can be clear vinyl. White tube can be clear vinyl. It is transferring the air form the source of the pressure change to the air pressure switch. The color and shape of the outside of the tube will not make a difference.

The only thing I would check is the direction of any arrow on the tube. You know if the arrows are backwards the air might get confused and go the wrong way. I always purchase tubing with no arrows just for that reason.

Italic = Sarcasm

Slowhand63

Ed - thanks.  Just what I hoped for/needed…

109A_5

Hello @Slowhand63,

Without the furnace model number this is the best troubleshooting info I have found. The Pressure Switch appears to monitor two different pressures. Inducer pressure apparently closes the the switch and then if vent pressure becomes too high the switch will then open and shutdown the furnace.

The Pressure Switch and system pressures can probably be tested, monitored and / or verified with a home brew manometer (clear tube with water) easy to build and a 'Tee' adapter fitting. Don't get water into the equipment. Use the multi-meter to monitor the Pressure switch state. The other working furnace could be used for 'Normal' pressure references. Do the broken one first to get comfortable with the setup.

Slowhand63

Thanks for the suggestion.  I’ll see what I can rig up tomorrow. 

FYI model AUC1D120A9601AD

Mad Dog_2

Any luck getting Robert O Brien out there?  Mad Dog 

109A_5

Hello @Slowhand63,

I know it has been mentioned before, but make sure none of the hose ports are plunged up with debris.
From a more appropriate manual, the information looks pretty much the same.


How I believe that pressure switch operates in your case, what I don't know is the actual trip pressure for yours, I would think maybe a few inches of Water Column or less. With two 'Tee' hose adapters you can see the differential pressure across the Pressure Switch's Diaphragm.
Actually if I was in your situation with the same redundant furnaces I would get 4 'Tees' and enough hose to set up an identical manometer on each furnace and compare them in real time.

Slowhand63

The switch spec is 1.4” wc. 

JUGHNE

I had intermittent pressure switch codes on a Nordyne 90+.
It was recommended to increase the port size for the hose connection on the collector box (not inducer). I used office sizing bits with a 1/4" hand driver to increase the opening, maybe 3-4 sizes larger than original.

You do not want to over drill as there is not a lot of plastic there, also don't go in too far to hit the heat exchanger. Hand turning bit only.

Been running since Christmas with no shut downs.

This trick was recommended by the supplier.....factory would not suggest such modifications....why...who knows?....liability....admitting there was a design problem?

Matt_67

Just to clarify an earlier comment, the order of events is important. If the fault occurs before the inducer starts, that would indicate that the control is seeing the pressure switch closed without the inducer running and assumes it is stuck closed. So it doesn’t start the inducer and gives the pressure switch fault. If it’s giving the fault after the inducer is running you’ll need a manometer to verify what’s going on. It could be a intake or exhaust pipe restriction or it could be a restriction within the heat exchanger.

JUGHNE

Another modification to exhaust piping.
Had at least 3 Nordyne's with pressure switch issues.
After several years the inducer fan did not have the power for exhausting.

These are shipped with a 2" PVC pressure tee, the exhaust goes into the branch (bull), the cond drain down one run and the exhaust up out the other run.

I changed these with the exhaust into the run, the drain out the branch and the exhaust went out the other run. Then a street 90 out the exhaust run.

The sharp 90 bend of the tee was adding enough resistance that the fan could not overcome. Going to a DWV street 90 for the turn made the difference.

All of these were piped by the book for distance and fittings.
I even use 2 spaced 45's instead of a DWV 90 for less friction.

Another situation IMO is the use of periscopes for the exhaust.
0-10 degree air will migrate into the outlet filling the exhaust with cold dense air which the inducer fan has to overcome.
This effect seems to happen even if the periscope riser is inside the heated building, not quite as much as external risers.

Slowhand63

Not much to report today.  Furnace ran fine. Bought some clear tubing to make a manometer, but couldn’t find the tees I needed anywhere (ordered online).  I’ll continue to monitor and will post if/when I learn more. 

Should anyone else have any ideas, suggestions, feel free to comment.  

Thx

Slowhand63

Nothing to report today…. The furnace ran fine overnight and this morning.  I’m waiting for a couple of parts to be delivered today/tomorrow to build a rudimentary manometer.

Friday night/Saturday morning forecast is for 9 deg F.  I’m expecting trouble then.  

I’ll post if something changes.  

Slowhand63

Furnace running fine.  I’m starting to think that after all this MAYBE it was simply a loose connection (at the pressure switch?).  I had hoped the error would return before I leave town tonight, but no such luck.  

I connected the manometer I built and connected it with a tee to the bottom of the pressure switch.  Currently pulling between 2” and 2.25” wc (manometer graduations, lighting, meniscus and angle impact accuracy). Later today I’ll check the other side of the switch and then F1 for comparison.  

I also ordered a Dwyer Magnahelic gauge that I’ll mount with a 3-way valve so I can switch between the 2 units and take readings.  That should arrive Tuesday.  

Photo FYI

Slowhand63

Resurrecting my 3 month old thread.  After a couple of weeks troubleshooting and replacing parts in late January my furnace ran fine for months… until this morning. 

As had happened then, I noticed about 7:15 this morning that the furnace seemed to be running for a long time.  I went down in the basement expecting furnace #2 to have no flame - and I was correct - no flame was visible. While looking through the sight glass the flame lit but was unsteady.  It was if I had a compressed air hose pointed at the flame.  Rather than the triangular or diamond shaped pattern Of blue flame I’m used to seeing - instead the flame was dancing all around - and then went out.  I immediately powered down both units (I didn’t think to check the control board light).  

Any ideas/suggestions of what I should be looking for?  I pulled one of the burners - but not sure what they should look like considering the unit is 10+ years old. 

All comments/suggestions greatly appreciated.  

EdTheHeaterMan

One of the tests I used to test for a breach (or crack) in the heat exchanger is to observe the flame with the blower on and the blower off. If the opening is large enough there will be a difference in air pressure on the cell that has the crack when the blower is on compared to the blower off. That difference in the air pressure will affect the flame. This is further verified with combustion testing instruments. This may be a little more involved when a furnace is twinned since both blowers operate in tandem. You will need to power off the furnace that you are not testing. Then operate the burners only on the problem furnace, and observe the flame. While the flame is operating, turn on the fan for that furnace and watch the flame on the suspect burner. If there is a substantial change compared to the other burners, you have a crack.