|
Posted by on February 18, 2007, 7:08 pm
There are lots of things that can cause this problem. 1/2 are
electrical faults and the others are mechanical.
Here are a few of the mechanical ones:
If the exhaust vent runs more than a few feet through an unheated
space at that outdoor temp and/or has the inappropriate slope back to
the furnace (1 " per 4 ft for eg, a pressure switch may shut the
system down due to water sitting in the pipe or ice build-up. It
thinks the exhaust is blocked and shuts down. If the exhaust runs
through an unheated space (including more than a few feet out doors)
it should be insulated.
The exhaust and the supply pipes could be reversed.
The installer forgot to install the baffles on the intake.
Electronically speaking, you need a qualified service tech who has the
trouble shooting manual for that furnace.
Fault 42 means that the venting motor, which is also an ECM motor,
like the blower motor whose speed is controlled by a circuit board, is
operating outside its valid speed range. You will also get the same
fault code if the venting motor has not started within 10 seconds of
the call for heat.
Some people sell these furnaces without having technicians
sufficiently qualified or prepared to repair them. The service tech
must have the Carrier trouble shooting guide for that furnace. It
will lead him through the appropriate test procedures to do the
diagnosis. Its about a 44 page manual. It might be available on the
Internet to authorized Carrier dealers.
I am an energy management consultant, not a service tech., but this
should point you in the right direction.
Doug
>I have a Carrier 58MVP120 that was installed in 2000. The unit fails to
>function when the outside temperature drops into the teens or lower. The
>inducer motor will spin up, but no ignition will occur and the unit will
>spin back down, followed by a 42 error code. When the temps come up above
>the teens the problem does not exist. The unit is located in a crawl space.
> I have placed a temperature sensor there and the temps stay above 50
>degrees at all times. The unit is under warranty and an authorized Carrier
>tech has spent about 6 hours testing the unit (3 hours on two different
>occasions). He did observe the problem. The thermostat is not at issue,
>apparently when isolated all of the components are fine. The tech has been
>as helpful as possible, but is as stumped as I am. I have on a few
>occasions placed a portable heater in the crawl space and heated it into the
>60's The problem does not occur as frequently when I do this, even when the
>temperatures drop into the single digits outside. This would seem to
>indicate that somewhere there is a freezing problem, but it is unclear to me
>how that could occur when the temps have always been at least in the 50s in
>the crawl space. If the pump dealing with the condensate was
>malfunctioning, could this be causing the problems? Any thoughts on ways
>to tackle the problem would be appreciated.
>
>John
| 
Yahoo! 
Google 
Windows Live 
del.icio.us 
digg 
Netscape 
XML Sitemap