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-   -   central unit will not come on ....please help (http://www.diychatroom.com/f17/central-unit-will-not-come-please-help-25619/)

guyasc 08-23-2008 03:02 AM

central unit will not come on ....please help
 
I recently replaced my 1978 GE exterior condensing unit....The inside unit iwas recently put in ( appx. 3 years old ). The inside unit is a self contained Fridgidaire.

After connecting everything the unit will not come on. I checked the condensor first. The capacitor checked out ok. The contactor on the condensor is new. I noticed that if I manually hold the contact in the exterior condensor operates fine.

Next, I checked the 24volt lines at the contactor (condensing unit). The lines did not show any voltage at all. I moved to the inside unit to check for power. I checked the main power outlet where the unit plugs into and it checked fine. I then checked the terminal where the 24 volt lines run from (long vertical black 5 screw plastic type). No power there. I noticed that the unit does have a red and green light on the same circuit board that the 24v terminal is set on. Both of these lights are currently off.

I did not notice any major lines feeding the circuit board. I noticed that the terminal with the 24v lines also held the wires going to the thermostat (Honeywell digital type ..Wal Mart). Is it possible that if the thermostat has a short it can feed back and not allow outgoing 24v? What have I not checked?

All breakers are good. There is power going to the inside unit so what could cause an interruption. I also noticed a single fuse on the circuit board (It was still good). Any suggestions would be greatly appreciated.

THX

buletbob 08-23-2008 05:48 AM

see if there is a red reset button on the condenser,?.where the disconnect switch feeds into the unit.

biggles 08-23-2008 07:45 AM

you should have a 24V at the board first thing(stat off/on doesn't matter)with power up on the air handler..the line power out at the condenser is looking for that 24V signal(to close the contactor you pushed in) from the stat by way of the air handler wiring out to the condenser.check the secondary right out of the TR in the air handler then into the board...if your digital on the stat is it lit on the LED screen.check R/C on the stat subbase should be a constant 24V...so your looking for 3 constants on that 24V ......at the stat..... on the board .....out of the secondary on the air handler TR

guyasc 08-23-2008 10:51 PM

thx for your time....

I did check and no there is no reset...It comes on when I hold down the conact and goes off as soon as I let go....whats strange is before I replaced the condensing unit the inside unit fan ran fine...It was very hot so even though it would not cool I just ran the fan in spurts. Now notta.....I replaced the t-stat wires from terminals on the inside unit circuit board to the thermostat...the wires were lugged twice by the installer so I went ahead and ran a new wires...still notta....

I figured I would check the float next....I have one of those units where the coil sits atop the furnace...I took the cover off but I did not see a float.....The coil pack is shaped like an A and there is a cover panel on it as well but I am not even sure if the float is in there.....

I also checked the circuit board (visually looked at the back for indications of breaks in the "lines") nothing.......still have power at plug in where the unit is plugged into....but no 24 volt.....the fan wont come on either (on the inside unit)...

1610 CUB 08-24-2008 07:15 AM

If I did not have 24 volts I would look for the 120 volt to 24 volt transformer. Also the door switch needs to be closed, or nothing will happen.

biggles 08-24-2008 05:10 PM

can you read 24Vs on the secondary of the TR in the air handler ...that is a constant as long as power is up un the air handler.when you changed the condenser and you shut the dissconnect down to do the work you might of thought the 24Vs was from there but it comes from the air handler.you might of sparked(shorted) the 2 thin wires that carry the 24Vs out to close the condenser contactor that brings the comp/cond fan on.if the 24Vs isn't on that TR you need to change it 115V/24V 40VA rating with a push button reset for the secondary mounted on it.


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