Carrier 58MVP120 - problem re: intermittent failure during extreme temps

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
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Uh... get a tech who knows what he is doing.
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Think slope and pitch and stop thinking temperature. Then read the installation instructions following the venting of the pvc piping closely. Then replace the thermostat. Its almost always the thermostat Bubba
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You have electronic problem I don't know how many electronic parts you on control card but you will find that problem is there. some solid state components do not like cold and will simply shout down or will not come on when temperature drops below rated limit and will operate normal as soon as they warms up Get Carrier to replaced it for you.

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This is an INDOOR residential furnace, not a roof-top. How would the circuit board feel the outdoor temperature? The colder it gets outside, the more the furnace has to run, but the ambient temp isn't going to be felt by the indoor board. It may or not be a board issue, but not because of the reason you stated.
--
Respectfully, Bob

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Bob_Loblaw wrote:

    To answer your question about the circuit board "Feeling the outdoor temperature," the unit is located in a crawl space. If it were my unit, I would look closely at the circuit board for poor solder joints. The symptoms have all the characteristics of a intermittent solder connection. No criticism intended, just throwing out a theory.
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Bob against my better judgment that you don't deserve answer I will gave it to you "Regardless were equipment maybe located" the connection failure occurs from stress, stress can be ? pressure, vibration or temperature solid state components are more septic to temperature then anything else. as Ken put it, it could be bad solder connection however unless there is some type of stress on the connection not likely it will fail.
wrote

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Here's what you said, Dido...
"some solid state components do not like cold and will simply shout down or will not come on when temperature drops"
I said .. "This is an INDOOR residential furnace, not a roof-top. How would the circuit board feel the outdoor temperature?" I also said it may be the board, but not because it's getting cold. You figure it out.
--
Respectfully, Bob

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Bubba, Dido and Bob,
Thank you for your thoughts on the problem. I will explore each one. I do appreciate your time and expertise. When I get it isolated (although this may take a while), I'll post and let you know what helped. Thanks again.
John
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............I'll be holding my breath......... Bubba
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Take the inlet pipe out of the combustion air box. I bet the furnace will fire up.
Sounds like an inlet blockage. Or a condensate problem. The colder it is the longer it runs, produces more condensation then can drain out. Look for blockages. You would need a tee and a dual port digital manometer to tell you exactly which side has the blockage.
-Canadian Heat
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Any tech who leaves without finding the problem is incompetent. Intermittent or not, experience and persistance will find any problem. Do the customers just keep paying? If the guy charges you once to diagnose a problem, keep calling him back under that same charge until he figures it out. Don't pay another cent until the problem is diagnosed.
And don't hire a guy named bubba! HAHAHA
-Canadian Heat
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On 18 Feb 2007 22:33:12 GMT, DANgER ( snipped-for-privacy@heat.com) wrote:

Sounds exactly like you DANgER..........INCOMPETENT!

Sounds like that leaves you out, hack-boi.

Sure they do, Canuck. The same way you do business. Just keep replacing parts till you get it right. And charge for each part.

You'd pretty much go out of business that way heat-boi.

Hell no. Nobody wants something done right and done right the first time. Keep dreaming Heat- boi of the North. You can only dream of being a ture professional one day. The day right after hell freezes over.

Bubba
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HAHAHA!
Case and point!
bubbs your as dumb as a dog.
:P
-Canadian Heat
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On 19 Feb 2007 19:44:03 GMT, DANgER ( snipped-for-privacy@heat.com) wrote:

Then that would make you dumb as dirt under a rock. Bubba
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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

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