No voltage at thermostat


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Old 05-15-21, 03:55 PM
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No voltage at thermostat

Hi,
I have honeywell thermostat and there is no voltage between R and any of W,Y,G when switching to "fan on" or cool mode.
transformer does show 24v in output side.
In control board, it shows 24V between R and C,W,Y,G.
Niether blower comes on when in any mode, nor does condenser start in cool mode.
condenser can be started locally by pressing contact.
what should I check next ?
 
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Old 05-15-21, 04:09 PM
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jumping R and G at control board, no effect
jumping R and Y, condenser starts
 
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Old 05-15-21, 05:25 PM
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jumping R&G works too - it takes 15-20 secs for fan to start.
So now problem is that jumping wires at control board starts blower and condenser but there is no voltage at thermostat, neither any of controls from thermostat work.
I don't see any overflow shut off device in attic.


 
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Old 05-15-21, 05:39 PM
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Tripped float switch?
Or more likely is a tripped Low pressure switch in the condenser due to low refrigerant charge. Make and model of outdoor condenser unit age & refrigerant type (R-22 or R-410A)?
Outdoor temperature also?

Is the filter present and if so is it clean and the right size?

Possibly more issues will cause this but I mentioned the most common ones.
 
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Old 05-15-21, 06:24 PM
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The "zoned thermal equalizer" box has a fuse in it. Check there.
 
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Old 05-16-21, 02:23 AM
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Welcome to the forums.

As Astuff mentioned....there is a fuse (2A) in the zoning control plus it may be powered by a separate transformer.

The pdf file below should be your unit.
 
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Old 05-16-21, 11:50 AM
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The "zoned thermal equalizer" box has a fuse in it. Check there.
Welcome to the forums.

As Astuff mentioned....there is a fuse (2A) in the zoning control plus it may be powered by a separate transformer.

The pdf file below should be your unit.
Sorry for maybe incorrect information however I never seen one of those before
I'm just used to people asking me for a purple "E" fuse and then look at me funny when I say go to any local auto parts store for a 3 amp fuse then say but this is not for a car?

 
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Old 05-16-21, 01:59 PM
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jumping R&G works too - it takes 15-20 secs for fan to start.
That tells you the fuse on the furnace board is good.

Sorry for maybe incorrect information however I never seen one of those before
Have never seen what before ??

If I've posted the correct install manual for the zone board.... it says there is a 2A fuse on the board.
There is no description of the fuse type and I don't see it in the pictorial so I've no idea what type fuse it uses.
 
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Old 05-16-21, 09:00 PM
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Have never seen what before ??

If I've posted the correct install manual for the zone board.... it says there is a 2A fuse on the board.
There is no description of the fuse type and I don't see it in the pictorial so I've no idea what type fuse it uses.
A zone board

The message you have entered is too short. Please lengthen your message to at least 25 characters.
The message you have entered is too short. Please lengthen your message to at least 25 characters.
 
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Old 05-16-21, 09:48 PM
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Ahhh.... yes. The 25 character minimum.

That's a zoning controller. There are two thermostats and two dampers connected to it.
Each thermostat operates its own damper. When either calls.... the damper opens and the proper heat or cool command is sent to the equioment. It should have its own 24v supply as it needs to control motorized dampers.
 
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Old 05-17-21, 07:48 AM
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sorry for some reason my reply did not post. It was zone controller fuse2ag 2am that was blown. (4.5x15mm)
I picked one from home depot (listed as 5mmX20 mm) but it is more likely 6mmx20mm.
Anyway I pushed it in and everything works. I have ordered correct fuse online and replace it in few days.
mine does not have separate transformer. thanks for all your help.

 
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Old 05-19-21, 08:43 PM
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Glad you got it fixed never seen one of the zone controllers before I just mentioned the normal faults for condenser not powering on PS: Don't manually depress the contacors button as this can damage the condenser the contactor or shock you with 240VAC if you touch the wrong parts

PPS: Those glass fuses were common in older cars and audio equipment I don't know if an urban myth but there is a story floating around that someone stuck a live round in their trucks head light fuse holder with the resulting BOOM!
 
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Old 05-19-21, 09:59 PM
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I don't know why they used a 2A 2AG except that it's an odd size. It's 5mm x 15mm.
A common protection fuse would have been a GMA 2. It's 5mm x 20mm.



 
 

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