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Old 11-09-2008, 07:02 PM  
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I thought we had eliminated the inducer motor and relay last week. The troubleshooting document you provided told us the limit switch is bad. Are we now getting power to terminal TH on the ignition control module?
What were the results from the troubleshooting guide in regards to testing the control module?
You could have a bad inducer motor (even though it is running) and does lend itself to explaining why the limit switch was toasted. However, before you go that route, check for blockage in the exhaust flu (backdraft damper closed, wasps nest, birds nest, dead bird, etc....).
If we can get some feedback on the ignitor module, we'll know more. After that, I'd start suspecting a bad ignitor. These are very delicate and should not be touch by the human hand and/or physically cleaned. It serves as both a flame ignitor and a flame sensor which, lends itself to how the system was working last season. These are symptoms but, not conclusive or exclusive.
What's that red button on the incuder flu housing?

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Old 11-11-2008, 11:07 AM  
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Default Works for now(fingers crossed).

Works for now(fingers crossed).
Turned out inducer blower was working, but not good enough to close the pressure switch.
Removed inducer blower, vacuumed inside, rotated fan manually.
Removed flue collector box to which inducer blower is connected, cleaned it too.
It wasn’t like I found something blocked or cracked to explain loss of pressure, but after putting all back in place furnace works!

I also found (well hidden inside) model # for furnace P2UDD06N03B01D.
model # in the 1st post of this thread was for cooling half, I’ve updated it now.
All the same there is no info on it anywhere, I wanted to find out about right high limit switch for this unit.
Does anybody know?

To be safe, will buy the 305F I had before
(I have 320F temporary).

Last edited by rodge; 11-11-2008 at 03:48 PM.
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Old 11-17-2008, 08:38 AM  
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Unit continues to work fine, tested by temps in the 20-s at night couple of times.
York part # for FLAME ROLLOUT switch pictured in post #12 is 025-26908-000 and I bought it real cheap here
Thank to kok328 and this forum.
Haven’t figured how to officially close the thread by myself, leaving it to admins.
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Old 11-28-2008, 12:24 PM  
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Rodge and kok328, I have a similar furnace that just began to fail recently. It starts to run the burners ignite and preheat the vents. The fan limit control rotates as the temperature rises and the blower motor kicks in. Very soon after this, it shuts down and repeats the cycle.

Rodge, it is a different model than your P2UDD06N03B01D. Your newer design is quite an improvement over my P1UDD06N03B01A. On my unit, all of the drainage hoses for the elimination of the condensation water are placed over blower motors or over critical circuitry. Leaky hoses have caused moisture to drip into the control boxes and corrode many connections. After cleaning the connections the unit still behaves the same. It is a very simple unit and has no error code LED. How would you begin to troubleshoot this unit?

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Old 01-11-2009, 05:36 AM  
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Default Troubleshooting Direct Spark Ignition Systems

Flame Rectification Is Vital Knowledge For Gas Heat Troubleshooters.

This article deals with flame rectification as it applies to direct spark ignition (DSI) modules. They are manufactured by a few different companies — Fenwal, Honeywell, Robertshaw, and White Rodgers, to mention a few.
The procedures for DSI flame rectification are pretty much the same for all manufacturers. It is a good idea, however, to check the specification sheets for the particular manufacturer’s equipment you are working on.
One of the primary uses for DSI systems has been on some power gas conversion burners. The initial problems with DSI systems have been eliminated by today’s technology — such things as multiple-try systems and what is called “soft lockout” (where the system will attempt several tries at ignition and, if it fails to ignite the burner, the system will shut down for 60 minutes, then go through another series of tries). This has prompted a comeback of DSI use with some manufacturers.

DSI Components And Specs

Standard DSI systems include the following components:
• A system control module that contains the electronics for regulating the system’s sequence of operation;
• A dual valve combination control (or two in-line single valve gas controls) that provides for positive gas shutoff and control of the main burner gas;
• Ignition hardware that provides for spark ignition of the main burner and monitors the presence of the main burner flame; and
• Auxiliary controls that complete the system — temperature controller, high limit control, transformer, etc.

DSI Control Modules

Honeywell DSI control modules include the S825A, B, C, and D; the S87A, B, C, and D; and the S89A. All modules are for low-voltage (24 VAC nominal) application on gas-fired furnaces.
When powered by a suitable 24-VAC, 60-Hz transformer and activated by the system’s temperature controller, they perform the following functions:
1. Check for a false flame condition (short to ground) before each startup. If a false flame condition is present, the module does not allow startup.
2. Generate a potential of 30,000 V (open circuit) at the spark igniter for direct ignition of the main burner.
Note: The S89A does not include a spark generator circuit. The S89A has an internal relay for activating a separate spark generator for ignition of the main burner.
3. Open the main valve(s) of the gas control(s) to allow gas to flow to the main burner.
4. Sense the presence of a main burner flame and discontinue ignition spark. If the burner fails to ignite within the trial-for-ignition period, the module goes into safety lockout.
5. If there is a loss of power, the systems will shut down safely. Startup is initiated when power is restored.
6. If there is a loss of the main burner flame, the trial for ignition is repeated. Safety shutdown occurs if the flame is not re-established within the trial-for-ignition period.

Gas Controls For DSI

The American National Standards Institute (ANSI) requires that all new DSI-equipped gas-fired appliances must have dual gas controls for positive shutoff of the main burner gas. This requirement can be met by using any of the following methods:
• By installing a dual-valve, “VR”-type combination gas control in the gas supply piping ;
• With a direct burner ignition valve , where the direct spark or hot surface systems use the same valve, and the two main valve operators work simultaneously under the control of the electronic module;
Note: For direct burner ignition, there is no pilot; leave the plug in the pilot outlet.

Ignition, Flame-Sensing Hardware

Ignition and flame-sensing hardware for DSI systems is available in several configurations:
• Separate flame sensors and spark igniters;
• Combination spark igniters and flame sensors that are mounted on a common bracket; and
• A single electrode igniter-sensor.
Generally speaking, the separate flame sensors and spark igniters are used together, or the single electrode igniter-sensor is used alone. However, some appliances use a different combination of these components; for example, an igniter-sensor for ignition and a separate flame sensor and spark igniter for flame sensing.
Whatever the combination, the system must have components, or a combination of components, for spark ignition and flame sensing.

Check Safety Lockout

1. With the system power off and the temperature controller set to call for heat, manually shut off the gas supply cock.
2. Turn the power on to energize the control module; begin spark ignition; immediately start timing.
3. Determine the number of seconds to safety lockout (spark cutoff). It should not exceed the time specified by the manufacturer.
4. After spark cutoff, manually reopen the gas supply cock. No gas should flow to the main burner.
5. Reset the system control module as described here:
• If the control module goes into safety lockout, it will remain locked out until the system is reset.
• To reset the system, adjust the temperature controller below room temperature, wait 30 seconds, and turn the temperature controller up to call for heat. Normal ignition should occur.

Final System Checkout

Start the system and observe operation through at least one complete cycle to make certain all controls are operating safely, according to the manufacturer’s specifications.

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