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Discussion Starter · #1 ·
I do mostly residential work but was asked by a friend to look at a weathermaker gas pack. There is no model number or serial number information, ID plates are missing. customer believes it to be a 7.5 ton around early to mid 1980. Also no schematic. I was wondering what the operating sequence is for the heat cycle. On a call for heat the pilot lights and that’s all, main valve won’t open. I replaced the gas valve (diaphragm was torn). How does the automatic pilot switch work? It looks like it breaks common? When the thermocouple senses a flame it makes the common connection? Is there a way to check the switch to verify?
Thanks for any help

Augie
 

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Discussion Starter · #3 ·
It doesn't look like that. I think its some kind of flame sensor. Carrier part number HH71PD024 Type 3049-52
 

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I do mostly residential work but was asked by a friend to look at a weathermaker gas pack. There is no model number or serial number information, ID plates are missing. customer believes it to be a 7.5 ton around early to mid 1980. Also no schematic. I was wondering what the operating sequence is for the heat cycle. On a call for heat the pilot lights and that’s all, main valve won’t open. I replaced the gas valve (diaphragm was torn). How does the automatic pilot switch work? It looks like it breaks common? When the thermocouple senses a flame it makes the common connection? Is there a way to check the switch to verify?
Thanks for any help

Augie
If you look in the control panel box, where all the electrical components are, you should see a "hidden" model and serial number. Depending the year.......earlier carrier equipment used various pilot flame proving methods. Knowing the exact year would be critical. Most likely though you are working with one that is using flame retification...not a thermocouple. On flame retification systems the pilot assembly has a hood with a rod. When the pilot lights, the flame is conductive and therefore provides a closed circuit to the rod which leads back to the ignition module.

If your working on an even earlier module without intermitten pilot(spark ignition) then you would in fact have a thermocouple...HOWEVER a thermocouple simply generates enough DC voltage (18v) to hold a magnetic valve open inside of the main gas valve. This allows the gas valve to open the main gas valve to the manifold. When a thermocouple goes bad it is not able to generate enough DC voltage to hold the magnetic valve open and therefore when you release the manual pilot "button" the pilot goes out.
 

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I do mostly residential work but was asked by a friend to look at a weathermaker gas pack. There is no model number or serial number information, ID plates are missing. customer believes it to be a 7.5 ton around early to mid 1980. Also no schematic. I was wondering what the operating sequence is for the heat cycle. On a call for heat the pilot lights and that’s all, main valve won’t open. I replaced the gas valve (diaphragm was torn). How does the automatic pilot switch work? It looks like it breaks common? When the thermocouple senses a flame it makes the common connection? Is there a way to check the switch to verify?
Thanks for any help

Augie
I Googled that pilot flame sensor number and this Carrier Weathermaker manual came up. It describes the sequence of operation for gas heat operation on page-4 and has multiple wiring diagrams and schematics in it, but it might be for newer models only, so don’t know if it actually pertains to your unit. Good luck with her.

http://www.docs.hvacpartners.com/idc/groups/public/documents/techlit/48_50a-3w.pdf
 

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Discussion Starter · #6 ·
The pilot assembly is a tube that runs the length of the burner assembly. Looks like a small ribbon burner. The spark igniter lights the pilot and the thermocouple is at the end of the tube. The 3 wires go to the gas valve. One goes to terminal 5 one goes to terminal 4 which also jumps to the spark igniter and the other goes to terminal 1
 

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The pilot assembly is a tube that runs the length of the burner assembly. Looks like a small ribbon burner. The spark igniter lights the pilot and the thermocouple is at the end of the tube. The 3 wires go to the gas valve. One goes to terminal 5 one goes to terminal 4 which also jumps to the spark igniter and the other goes to terminal 1
By your description your dealing with a pilot re-ignition system in which case that is not a thermocouple. Earlier models of the Weathermaker utilized flame rectification. Pilot is lit via the spark generator. Once the pilot flame ignites, the highly ionized flame completes the flame rectification circuit which, in effect, shorts out the spark to ground thereby "sensing" the flame. Once the pilot is proven the main gas valve opens, igniting the main burners.

Another variation of this utilizes a pilot safety, a monometal or liquid filled bulb that, once heated up, opens the main gas valve.
 
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