I have a Carrier 48SS-036100331-- (about 11 years old) and my house is
approx 1750sq ft. The heat works fine when the outside temp. isn't too cold
(ex. greater than 50 degreesF). However, when it is colder outside, the unit
frequently locks out. The exhaust fan continues to run, but the burner isn't
lit. I had to have my heat exchanger replaced last season. I vaguely
remember the technician saying it was likely there wasn't enough airflow, so
the exchanger was getting too hot which decreased it's lifespan. This made
me suspect that the limit switch was tripping. However, the led on the
controller board blinks 8 times when it's locked out, which corresponds to
"internal control fault" according to the schematic. I have opened all my
dampers to maximize airflow. When I flip the breaker off then on again to
the unit, the burner will light up again and will work for awhile and then
lockout again if it is cold outside. Here are pictures:
Any ideas? "Internal control fault" sounds like the controller board, but
why would it work except when it gets cold out? What is the best way to
troubleshoot "internal control fault" error?
look in the middle of the circuit board, see the two big square white
resistors and the two resistors immediately above them? One looks
like its been over heating....also the mounting holes/slots in the
ignitor assembly.....sand paper the metal around those mounting
locations as well as their corresponding mating surfaces where they
mount. you need a good grounding connection there...
too bad when they replaced your heat exchanger they didnt also replace
the totall rusted out inducer housing. Inside that inducer housing is
a totally rusted inducer blower wheel. the wheel should have been
replaced as well, as they tend to disentegrate
also, check for tightness on all stake on connectors and the edge
connector on the ckt board. those units are notorious for
over-firing. be sure to check and set the pressure at the gas valve.
your service tech should have de-rated the burners if its overfiring
see that round black gizmo with wires coming out of it at the back of
the inducer motor? thats the Hall-Effect sensor, a total piece of
shit. It tells the control board the inducer motor is running and
its ok to open the gas valve and spark the ignitor. It is a piss-poor
design though, as the inducer motor can be spinning a totally rusted
out inducer wheel. So when the gas ignites, you get major flame
roll-out, which usually burns all the wiring up. Did I mention I LOVE
finally, take a shop vac to the crap in the bottom of the burner
compartment. cleanliness is next to godliness.
ps- error code 8 is carrier's way of saying.....get ready to spend
the big bucks....
On Sun, 21 Jan 2007 00:34:01 GMT, firstname.lastname@example.org wrote:
Shhhhhh. Cmon Fish........dont give away all the secrets.
We just luvvvvvvvv those Carriers. Its the best equipment on the
planet <snicker, snicker> Well, they have to be right? All their
commercials say so. :-)
Who else can go through about 10 revisions of a shitty circuit board
and keep charging the customer for it? Carrier......Thats who. We love
you. Just like money in the bank
Thanks for the reply.
Yeah, those two resistors do look like they have been overheated.
I cleaned the ignitor and flame sensor and where they contact the mount
yesterday (with steel wool and wire brush). I thought that might have done
the trick because the heat worked all day yesterday afterwards and this
morning (which was very rare beforehand). However, it was locked out when I
got home today. :(
Soap and water (while powered up of course) was sufficient. Not only is the
heating up and glowing red, but it also plays music now.
Seriously, I plan to check all the connections to make sure they are secure
and everything, that should be, is well grounded. If that doesn't fix, I
have to assume the circuit board needs to be replaced.
??? Leave it powered up and scrub the back of the circuit board with oo
wool to get the soldered connections clean???
Is this a joke? I don't know much about heating and cooling but I'm an EE
is not a good idea for any circuit board. It will short out components and
likely damage the board. If there is high voltage on the board it could
electrocute a person. It would also not fix any bad connections on the
back of the
This has to be a joke for people who know better but some non-technically
person may actually try this. Not very funny.
guard0g had written this in response to
I had a similar problem (as have many others) and hope this information
Intermittent furnace lockout with Internal Control Fault (8 flashes),
sometimes accompanied by the "modified fan blower delay" fault (1 flash).
Problem occurs especially when the temperature falls below 32 degrees.
Exhaust Fan continues to blow after lockout. Checked rollout switches and
flame sensors, no problem.
Excessive vibration triggering the relays on the Integrated Control Panel,
which cause the internal control fault (usually the vibration can be felt
by touch on any part of the unit)
Dampen the vibration to the control panel using high-temp flame-resistant
Vibration most likely due to imbalanced exhaust blower wheel (cage wheel
inside the blower that pushes flame exhaust out of the unit). Replace
blower cage wheel.
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