Help with outside unit and 24 volt


Old 03-06-06, 11:29 AM
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Help with outside unit and 24 volt

Ok... I am at wit's end...

Here's the deal...

The inside fan works fine..
My outside unit does not turn on at all.... Not for A/C ... Not for heat...
I checked everything possible...
I jumpered the Y and R and still nothing.. I went out to the unit and opened it up..
I found that I am getting power outside..
I am getting 240V into the contactor... Everything looks good from the capacitor...

When I push in the 24 V switch... The condenser and the motor turn on.. I even held it in for a period and cold air was blowing...

So, I figured that for some reason.. I am not getting 24 volt across the contactor..
I changed out the contactor for a new one...

That led me to the board inside the unit...
When I run the voltmeter across the R and Black/Blue (return 24v)... I get 24 Volt...
So I know that power is there...
For some reason it is not shorting between the R and Y...

I even unplugged one of the leads from the contactor... and touched it directly to the R... and everything kicked on...

One of the questions I would have is...
Inside the garage, inside the handler... If I run a voltmeter between R and Y, should I get 24V.

At the Tstat... when I voltmeter R and Y... I do get 24v.

Any thoughts....

Old 03-06-06, 12:02 PM
Join Date: Feb 2005
Location: kansas
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Please be careful! I know you want to do it yourself, but what you are doing isn't safe. May want to call a pro in.
Old 03-07-06, 04:14 PM
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My money leak in the coil. Let me know.
Old 03-07-06, 07:58 PM
Join Date: Nov 2005
Location: race city, usa, mooresville
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i know that this might be the same ole song and dance, but i wish posters would at least tell us what type of system they have, the age, size, any work performed recently, etc. the more info we have on the system, the quicker we are to be able help you solve your problem.
and by the way your board is bad.

Old 03-08-06, 04:11 PM
Join Date: Nov 2002
Location: Massachusetts
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check the wire that runs from the thermostat to the air handler, usually 4 wires at least, and jump the low voltage terminals R&Y together, if this starts the outdoor unit, either the thermostat or its' wire is the problem.
If it doesn't start, check to see if you have 24V going to the outdoor unit. This should be checked at the low voltage terminal strip also, only this will have only two wires being used in the bundle. If you have 24V there, check it before it goes to any type of switches. If you still have 24V, your still good, but if it goes to a freon pressure switch, and its open ( test this with the air handler off and OHM the switch) it should show continuity, if not, you have likely contaminated the system by sucking in air when you pushed in the contactor, and need a tech anyhow...

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