Carrier 58sxa intermittent problem

Hello, I have a Carrier 58SXA that I don't know what to do with next. When the thermostat calls for heat, most of the time the furnace works. Sometimes though it just does nothing; no inducer motor, no noise, nothing. It shows heat on the thermostat but the temperature in the house keeps falling and the furnace is silent. I replaced the control board. Same thing. I replaced the inducer board and pressure switch. Same thing. I replaced the ignition box. Same thing. I replaced the pilot assembly and flame sensor. Same thing. I replaced the limit switch. Same thing. I replaced the thermostat. Same thing. I'm stumped. I've checked the wiring down from the thermostat. Everything is as it should be. Our local Carrier man doesn't know what is wrong. I haven't replaced the gas valve or wiring assembly. When the furnace works, it works great. Thanks always Eddie
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You need to break out the meter and do some actual testing when it won't start. You're just throwing parts at it.
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On Thu, 31 Jan 2008 14:31:43 -0600, "Edward R Morris"

You need to replace the wiring assembly FIRST! Second, replact the thermostat again. Then finally, replace the gas valve.......IN THAT ORDER! That should take care of it for a while. Bubba
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That furnace was made in about 1986, and according to my local Carrier wholesaler tech guy, "that furnace had problems". LOL The board was originally designed to shut the inducer off when the call for heat ended. Also, the combustion air intake would allow water to drip down onto the pilot assembly. The replacement board would makes the inducer run for 15 seconds after the call for heat ends. How many terminals does your replacement board have?

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Hi Bobb, The replacement board has terminals for Y, W, H, R, GH, C, G, EAC-1 and EAC-2. I've noticed the inducer motor runs for awhile after the call for heat has ended. I've read some of the problems this furnace has. Fortunately there is no sign of water dripping on the pilot assembly. I'm beginning to know this furnace more intimately than I want too..LOL. I would buy a new furnace but money is the problem.
Bobb, what do you think could be a (the) problem with my wonderful Carrier 58SX?
Thanks, Eddie

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I honestly don't know what the problem is, I can't see it from here. Assuming you have good voltage and gas pressure, if it stops in the same spot each time it malfunctions, then that's where the problem is. The thermostat signals the inducer motor relay built into that board you replaced. You need to put a meter on each terminal, one at a time.
Was "your local Carrier man" a service technician? If so, did he actually come out and look at the furnace, or did you just phone and ask questions? If a technician came out, was it malfunctioning when he was there?
A trained tech should have all the right tools and either know or have available a Carrier "Sequence of Operation". If not, it's available to him (not you) on the Carrier web site. It tells him what should happen and when. If it's malfunctioning when he's there, he should have very little trouble.
BTW, unless a heater was damaged by water, lightning, etc., multiple parts replacements are rare. I understand your need to save money, but if that furnace misfires, you're in for more excitement than any sane man really should want. Do yourself a favor and call someone qualified.

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Uh, the fact that it's 22 years old doesn't mean anything to you??
JK
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Hell no!!! they are supposed to last FOREVER!!!, or thats what they want to think.
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Big_Jake wrote:

58SXA is not 1986. [58PAV / RAV would be however.] 58SXA is a 10 year old product. Try somthing around 1997. And with the serial number, the age can be pinpointed.
--
Zyp



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Isolation relay.
If this was already proposed, then disregard. I didn't read all the responses to your question.
I recall a similar problem back in the late 'eighties when I was doing residential work. Same deal, intermittent no heat. Turn the power off to the furnace, back on, normal heat cycle starts and continues to cycle for undetermined amount of time until next failure. This problem arose when changing from a mercury switch thermostat like a T87F, to a solid state control thermostat like a Chronotherm or similar.
The fix: install a 24 volt isolation relay on the W (heat) circuit between the thermostat (t) and the board (b). When the call for heat satisfies, the relay makes a clean break between Wt and Wb, same as the old mercury switch thermostat did, eliminating any feedback or trace through the solid state thermostat which they were stealing to charge up a memory chip or battery or whatever they do.
Wt to one side of the relay coil. Cb (24v common) to the other side of the relay coil Rb (24v) to relay switch common Wb to relay switch NO (normally open).
Tom Beckner
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Tom Beckner wrote:

That's nice, there's no isolation relay needed on this model.
--
Zyp



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