Replacement pilot assembly for Carrier 58ssb


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Old 02-11-09, 03:58 PM
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Replacement pilot assembly for Carrier 58ssb

I have followed several threads detailing problems with the Carrier 58ssb furnace. I have had similar problems where the furnace starts fine upon a call for heat: inducer fan turns on, pilot lights, burners come on, blower kicks in and then the burners shut down and then relight several minutes later.

I have traced the problem to the 3-wire pilot/sparker via jumping the yellow and white wires. When I did this the unit ran with no premature shut down of the burners. Cleaning the pilot assembly didn't solve the problem. Assume that the pilot flame moves away from the bimetal strip allowing it to cool down and trip the gas valve off.

So, today I purchased a replacement 3-wire pilot assembly (PS730A: replacment part for LH68005) at my local HVAC parts store. When I installed this new pilot, the sparker sparked, but the pilot never lit. I let it spark for several minutes, however, it appears that the gas valve never accuated the pilot line. When I put back the old pilot, it worked fine, except for the short cycle.

I would have assumed that the connections were simple: gas pilot line, sparker and 3-wire plug. But I guess not..

Wondering if my new pilot is defective or if something may be up with the voltage requirement?

Any help would be appreciated!!
 
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Old 02-11-09, 06:59 PM
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Are you sure you have the nat gas orifice installed and not the LP one??
 
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Old 02-11-09, 07:09 PM
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The package says natural gas so assumed that it had the correct orafice supplied. It was a different shape that what was in the old pilot assembly, but the hole size appeared about the same.
 
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Old 02-11-09, 07:46 PM
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I'm interested in seeing what you did when you jumpered the white and yellow wires, but the circuit diagram I have doesn't list the color of the wires. Please identify which color wire is connected to the terminals on the electric gas valve --- presumably terminals 1, 4 and 5.
 
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Old 02-11-09, 07:59 PM
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SeattlePioneer

Here is where the wires go from what I can see:

White to terminal 1
Green to sparker to terminal 5
Yellow to connector next to pressure switch then brown back to terminal 4

I haven't messed with the wiring. I simply disconnected the old pilot, installed the new and then connected the molex connectors.
 
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Old 02-11-09, 08:05 PM
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Originally Posted by gandalfirons
When I installed this new pilot, the sparker sparked, but the pilot never lit. I let it spark for several minutes, however, it appears that the gas valve never accuated the pilot line. When I put back the old pilot, it worked fine, except for the short cycle.

Was gas coming out of the pilot burner? You seem to be saying that no gas was coming out, but it's important to know for sure.

When you have the new pilot switch in, measure the AC voltage between "C" or the chassis ground and terminal 4 and then again between ground and terminal 5.
 
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Old 02-11-09, 08:23 PM
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It was sparking, but I didn't detect any gas (smell). The old pilot lights almost immediately upon sparking.

I will have to check the voltages tomorrow or Friday as it is getting late. I will also check the voltages for the two you suggest with the old pilot (currently in place).

I assume the "C" refers to the "C" on the control board?
 
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Old 02-11-09, 08:35 PM
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Originally Posted by SeattlePioneer
When you have the new pilot switch in, measure the AC voltage between "C" or the chassis ground and terminal 4 and then again between ground and terminal 5.
That's terminal 4 and terminal 5 on the gas valve.

Both those terminals need to be energized with 24 VAC for the pilot gas to turn on. If one is not energized it explains why you are getting no pilot gas and points toward which part of the circuit is likely to be the problem.
 
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Old 02-11-09, 08:41 PM
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Originally Posted by gandalfirons
I assume the "C" refers to the "C" on the control board?
---------------------------------------------------------


Yes.
 
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Old 02-15-09, 08:22 PM
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Well, I finally found time to mess with the furnace again. Before I attempted to measure any voltages, I replaced the old pilot assembly with the new one. After restarting the furnace, the pilot assembly work as it should.

Unfortunately, the same problem exists. The burners turn on for 4-5 minutes, go out for 1-2 and then relight starting the sequence over and over. One thing I did notice was that the shape of the pilot changes when the burners light. It appears as if this causes the flame to move a bit away from the bimetal strip. I assume that this would cause the burners to then trip off when the strip cools down.

Any ideas on why the pilot would change so much when the burners turn on?

Furnace works and heats the house, just a lot of cycling on and off.

Thinking it may be time to get a new furnace. Hopefully we can make through the heating season without any other problems.
 
 

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