Thermal Zone heater problem


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Old 10-26-07, 04:41 PM
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Thermal Zone heater problem

Hi everyone,
I have a Thermal Zone furnace and it will not stay running. It blinks 3 times and a code says PRESSURE SWITCH STUCK.
Any ideas what the problem could be? I guess if you blow on it or thru it it will work for a minute...
Thanks for your advice...
 
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Old 10-26-07, 07:00 PM
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Originally Posted by Cyndy View Post
Hi everyone,
I have a Thermal Zone furnace and it will not stay running. It blinks 3 times and a code says PRESSURE SWITCH STUCK.
Any ideas what the problem could be? I guess if you blow on it or thru it it will work for a minute...
Thanks for your advice...
Does the combustion air motor start?

Things to check:

cracked switch hose, obstructed switch hose, Bad switch, combustion air fan not running, combustion air fan not running at full speed- IOW bad bearings slowing it down, combustion air fan wheel rotted away or loose on the motor shaft.
Let us know if find anything.
 
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Old 10-26-07, 07:13 PM
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Thanks for your response but those are all fine, I guess we know it is the pressure switch but don't know if it can be cleaned or has to be replaced. It says PRESSURE SWITCH STUCK CLOSED...
Thanks again
 
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Old 10-26-07, 07:29 PM
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Originally Posted by Cyndy View Post
Thanks for your response but those are all fine, I guess we know it is the pressure switch but don't know if it can be cleaned or has to be replaced. It says PRESSURE SWITCH STUCK CLOSED...
Thanks again
usually replaced.
 
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Old 10-26-07, 07:57 PM
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Cyndy,

Codes do not always know the root cause though. The pressure switch may be closed, as claimed, but there might be a reason why it is closed, other than a faulty switch.

The pressure switch senses pressure from the drafting/flue process. The pressure in those rubber hoses is extremely minute'.

You were able to make the furnace work by sucking or blowing on it by overriding the natural forces involved. This may or may not mean it is the pressure switch itself. It could be that the pressure is just a hair off, that when the diaghram inside it moves, it is not moving quite enough to engage the electrical contact points.

You may be able to effectively test the diaghram by sucking in or blowing through one of the vacuum tubes and pincing off the hose quickly. If it holds without you either seeing the diaghram's plunger move (you can on some models), or hear it click afterwards - then it is good. But if you see it move, or hear it click after a while of holding the line pinced closed, then it is bad.
 
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Old 10-26-07, 08:14 PM
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Thanks ecman,
I don't see a diaghram or plunger to test that but blowing in the tube definetely starts it up...
 
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Old 10-27-07, 01:41 PM
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Now you just have to do as I suggested so you know if it is indeed the pressure switch itself, or instead if the switch is not responding because the suction or push in the line you blow or suck on is insufficient due to other things like dj suggested in a post below.
 
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Old 01-30-09, 06:17 PM
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all zones stay on at same time

I have a TZ-3 Honeywell Total zone sys. and all zones stay on. It should be on each station until it reaches temp then switch to the next... it doesn't.
 
 

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