Rheem Classic 90 Inconsistent Operation

Old 12-31-12, 07:25 PM
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Exclamation Rheem Classic 90 Inconsistent Operation

Hi, I have a Rheem Classic 90 that was installed in my house when it was built about 7 years ago. It hasn't become a serious problem yet, but something is failing on the unit and I don't want to be left in the cold this winter. 70% of the time, the unit starts up and works properly. The other 30% it fails and shuts off. I've searched all over the web and can't find anything as goofy as what i'm experiencing. The heater sometimes seems to be starting up in the the wrong order.

This is what happens when it fails to start:

1. Exhaust blower turns on
2. Ignitor turns on and glows for about 10-15 seconds, then shuts off
3. Gas valve does not open and burner does not attempt to light
4. Main blower turns on circulates cold air for about 2-3 minutes
5. Main blower and exhaust blower shut down
6. Ignitor turns back on and gas valve opens
7. Burner flame "pops" and goes out
8. Gas valve shuts off

Usually on the next attempt it will start fine. Although, it has done this 2 or 3 times in a row before, with a 2-3 minute period inbetween attempts. It seems to be doing it more frequently now. This time I smelled gas after a failed attempt sitting about 15 feet away from it. Not stong, but enough for concern. I'm an automotive HVAC tech, so this is a little out of my expertise.

A technician visit really isn't in the budget right now, so I'm hoping there is something I can diagnose and repair with your help. I do electronics repair on the side, so I do have testing equipment.

I'll try and get a video of this thing if I can catch it in the act.

Edit: If I peek through the window on the lower door, there's a green and an orange LED lit.... if this means anything.
Old 01-02-13, 12:23 PM
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Usually the diagnostic codes are posted on the inside of the fan compartment cover. Look for those codes and post the descrip[tion of the codes being signalled by the ignition control.

There might be more than one.

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