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Old 12-14-2010, 07:58 AM  
accokeek89
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Remove the hose from the low pressure switch and plug. The control board will then run the inductor fan at high speed which should cause the high switch to close and allow the ignition phase to begin. This should allow the furnace to run on high only till you can get a new low switch.



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Old 04-30-2011, 09:31 AM  
Louieg
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Default Similar problem

I have a similar problem. I have ruled out pressure switch which I have replaced. Exhaust seems unrestricted outside the house. There is not enough vacuum for the pressure switch to be activated. Could this be a heat exchanger problem?



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Old 09-17-2011, 12:48 PM  
NATEHAWK
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Hello everyone I'm new to the forum but see this site is very informative. Right now m having he 3 blinking lights error on my Trane XE90. I removed the inducer blower and it spun free no blockage. I also checked outside in the pipes and they looked good also. Now I removed the little rubber hoses starting with the one on front of the pressure switch and the switch spilled out a good amount of water. I take it that's my problem? I let it drain and took off the pressure switch and drained all the remaining water out of it. I'll hook everything back up and see if it work now? What could be the cost of that switch filling with water? I'm putting two and two together and thinking something has to be clogged. What should I check?

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Old 09-19-2011, 04:43 PM  
hvactechfw
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Originally Posted by NATEHAWK View Post
Hello everyone I'm new to the forum but see this site is very informative. Right now m having he 3 blinking lights error on my Trane XE90. I removed the inducer blower and it spun free no blockage. I also checked outside in the pipes and they looked good also. Now I removed the little rubber hoses starting with the one on front of the pressure switch and the switch spilled out a good amount of water. I take it that's my problem? I let it drain and took off the pressure switch and drained all the remaining water out of it. I'll hook everything back up and see if it work now? What could be the cost of that switch filling with water? I'm putting two and two together and thinking something has to be clogged. What should I check?

Thanks
Nate
The switch needs replaced if it was water logged. Check the drain trap. Remove it and run water through till all the debris inside is gone. Also, make sure the drain hoses from the inducer and cold header to the trap are free and clear of debris. This is what would have allowed water to reach the press. switch.
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Old 10-09-2011, 06:18 PM  
lostpilot28
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Hi everyone, I've been dealing with the same problem for a couple years, but it's getting worse. In the past, the unit would cycle a couple times before igniting and providing heat. Toward the end of last spring I awoke to a few cold mornings and found that if I pulled the small hose off the front of the pressure switch, I'd hear the 3-clicks and it would start working. Now it's getting cold again and doing the same thing, so I ordered a new pressure switch. Same problem!

So, it appears that the front side of the pressure switch isn't getting enough pressure. What I've noticed with the new pressure switch is that if the draft blower starts, and I'm getting the 3 blinks on the LED panel, I can pull the front pressure switch hose and blow air toward the hole and it will start. I'm not even touching it, just blowing air at it. This tells me that the pressure on the back-side of the switch is VERY close to being enough to close the switch. What could cause the pressure to to be like this? I've checked all the vent lines, in and out and they appear very clean. I don't have a sag in the line, so I'm stumped. Any help is greatly appreciated!

Also, how do you know if the 1.40" WC switch is right for my unit?

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Old 10-09-2011, 07:29 PM  
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Remove and clean the drain trap.

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Old 10-09-2011, 07:48 PM  
lostpilot28
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Thanks for that, HVACTech. I was looking at that thing today, but I didn't see how it could have any effect on the pressure switch. Can you elaborate a bit?

Update: It took me about 15 minutes to remove, clean and reinstall the trap, then test. It didn't fix it...still getting the 3 flashes.

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Old 10-10-2011, 03:35 PM  
lostpilot28
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Thanks for that, HVACTech. I was looking at that thing today, but I didn't see how it could have any effect on the pressure switch. Can you elaborate a bit?

Update: It took me about 15 minutes to remove, clean and reinstall the trap, then test. It didn't fix it...still getting the 3 flashes.
Also, would a weak draft inducer motor cause this? My heater is 8 years old and I would think they'd last longer than this. Is there a way to test or check the motor or impeller (whatever it is) to see if it's good?
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Old 10-10-2011, 04:25 PM  
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the proper way to find out whats going on with the unit is through the use of a dual port manometer or a magnehelic. These are specialized tools. You may want to call a pro. But before you do.... Do you hear water sloshing around in the inducer while it is running? Follow the pressure hoses back from the switch where it enters the cold end header of the heat exchanger (to the left of the inducer... should be a clearish hose) make sure that port is free and clear of any debris.... use a piece of wire or a long drill bit and put it through the port to ensure it is clear. Much beyone that and you will need a pro or some specialized tools.

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Old 10-10-2011, 04:28 PM  
lostpilot28
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Thanks again...I've cleaned the hoses to the pressure switch, and I've verified they're not blocked on the header. There is no water sloshing around in the inducer. Any further ideas?



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