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Discussion Starter · #1 ·
Furnace 2003:. C9MPD050F12B1
Stopped working, no codes,but gas valve was solid green light (not heartbeat), and nothing was happening (call for heat click but nothing else). Tech came out and stated gas valve and circuit board need replacing. Had both those done.

After replacing, call for heat and inducer motor starts and then blower motor and still no heat. Circuit board throwing code "flame sensed out of sequence" and gas valve is throwing code "limit switch open." I jumped all the limits switches, individually and all at once and gas valve still shows same code.

My smart valve has three wire harnesses that plug in, the largest Male wire harness doesn't fit properly and needs to be giggled or held a certain way in order to make a good connection.

I am without heat on Thanksgiving and recently lost my job and don't have loads more money to throw at this. Tech suggested I replace igniter but isn't sure that's the problem. I'm at a total loss on what to check or how to fix. Any help would be amazing.
 

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I’m not a tech but flame sensor may be working as designed to prevent a fire or worse.
I would call owner of HVAC shop owner for refund on parts that didn’t need to be replaced etc…
Pros here will likely come along with better advice.
 

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Discussion Starter · #5 ·
I’m not a tech but flame sensor may be working as designed to prevent a fire or worse.
I would call owner of HVAC shop owner for refund on parts that didn’t need to be replaced etc…
Pros here will likely come along with better advice.
Thank you.Im hoping to get some good advice, I definitely need it!
 

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May be that the male molex that isn't fitting right. Was the problem all along. Its a common problem.

Yes, call that company back, they changed parts, and left with it still not working. Tell them you want better tech.
 

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I order them from the HVAC supply house for the brand I need it from.
 

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Discussion Starter · #9 ·
I order them from the HVAC supply house for the brand I need it from.
Thank you,I will try to find somewhere else I called two HVAC places Wednesday and they state they do not sell them. I just found some Molex receptacles to buy online from some tech company,but shipping is insane.
 

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Discussion Starter · #15 ·
Need to check every circuit individually with the plug out, looking for continuity.

Keep in mind, the plug can get loose so you may not pick up the problem.
Where exactly should I place the multimeter leads in order to check for continuity?
I ultimately believe the plug needs replacing but it doesn't seem like a common part I can just buy, remove cables from other receptacle and place into new plug.
 

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Where exactly should I place the multimeter leads in order to check for continuity?
I ultimately believe the plug needs replacing but it doesn't seem like a common part I can just buy, remove cables from other receptacle and place into new plug.
one lead on the pin of the plug on the end that plugs into the valve, another on the wire lead going from that plug, set to ohms.

Disconnect what's connected to wire lead being tested.


Testing isn't fool-proof as the issue could be that part of the pin in the molex plug just doesn't make proper contact.

An issue like this is hard to sort out and really you should be contacting the company that replaced the parts, ask for another tech as beenthere suggested.
 

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Where exactly should I place the multimeter leads in order to check for continuity?
I ultimately believe the plug needs replacing but it doesn't seem like a common part I can just buy, remove cables from other receptacle and place into new plug.
If you look at the wiring schematic for the unit it’ll show you what pins do what. You'll have to dissect it from there as to what does what.
But whatever the issue is has to be determined before buying parts.
I’d suggest calling the company back that charged you money and didn’t fix anything.
 

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Discussion Starter · #18 ·
I have completed all repairs myself. I have called multiple HVAC and electric supplier stores who all state they do not sell just a molex connector. I can but the entire wire harness, but it's $200 and I only need the single plug. Any other suggestions on where to look?

Thanks in advance!
 

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Try radioshack.com (anybody still remember them) or give them a call and tell them what you are looking for. I don't think there are any more stores here in the US you can actually go to, but they still do business online.

They have all kinds of molex connectors, doodads, etc., you can browse through. Maybe you can find something that will work.

Hope you can find a solution soon that will work for you.

https://www.radioshack.com/search?type=product&options[unavailable_products]=last&options[prefix]=none&q=molex connector*
 
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