Whisperheat dead


Old 11-14-08, 07:46 AM
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Whisperheat dead

I have a Lennox Whisperheat natural gas furnace.

Problem: Will not start at all in heat mode.

Worked 11/09 - did not fire on 11/10 - no problems before that.

Ignition Controls: Johnson Controls G776RGD-11, 24vac on THS, no signals elsewhere. LED is OFF all the time. Did hard reset (powered down for 1 hour) LED didn't even flicker when restarted.

No pilot light, cleaned flame sensor with a dollar bill.

When I jumper between P.V. and THS the gas valve opens but there is no spark.

Unit works fine in AC mode.

there is 24vac across both flame roll out sensors.

Edit: Electric Damper door is ALWAYS open with power turned onto the unit.

Right now I think I need a new ignition module, but in the off chance there is another external signal it is not receiving, where would I look and what am I checking for?

Is there a decent replacement since no one has the Johnson controls in stock?
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Old 11-14-08, 03:53 PM
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Do you have power coming into the Johnson Control module, at least at the closing of the low volt safeties?

If you have a module with a metal plate on it or otherwise is gounded, I'd back out the mounting screws and retighten, to freshen up the ground, and also remove all spade connectors, and reinsert to make sure you have good contact. This might only help if the module is receiving power to it, of course. Otherwise, you'd naturally have to figure out the chain of command as to why power is not reaching it.

I recently had to replace 2 of the most simple (Johnson Controls) modules you have ever seen, on a Lennox. And the supply house charged me $190 a piece, including charging us $10 for shipping. Modules that look like this are usually $80 or less. I expressed my displeasure. The heating pro at the supply house even told me himself that modules like that usually only cost $70-80. I'm not sure who was the big profit reaper here. I plan on calling Johnson Controls to see what these things are supposed to sell for. Seeing that 5 more of them might be going out in the near future.

A heating contractor I deal with will often substitute parts, by using something different out of his cube van. But he is someone licensed in the HVAC business. I am not in such a position to offer tips on such retrofit changeouts.
Old 11-14-08, 04:15 PM
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Replace that control with a Honeywell 5l190 or a number similar. I don't recall the exact number that is a replacement for the G776. That control on the Whisperheat has been a problem. Of course I'm not saying that is your problem without proper troubleshooting.

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