Outside Unit Not Coming On

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Outside Unit Not Coming On

by Bob
(NJ)

I have a Carrier central air unit (model 38ed048300)manufactured in 1983. It has been serviced several times over the years. When I set the thermostat switch inside my home to "cool" the furnace blower comes on and everything appears to be ok at the furnace.

The fan on the external unit does not come on at all. I checked the two cartridge fuses (50A) in the fuse box near the AC, and they checked good with an ohmeter. When I had the fuse block out, I checked the voltage at the fuse box and there was about 25v AC across each of the fuse terminals. This voltage was there even with the thermostat switch inside the house set to "Off".

I also checked the main circuit breaker box in my garage to see if any breakers were tripped but none were. I even turned each circuit breaker off and then back on. It made no difference.

When I look inside (through the vent holes) my AC unit, everything appears to look relatively new. Should I take the cover off the AC unit and look more closely inside ? Is there anything else I can check ?

I appreciate any help you can provide.

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Outside Unit Not Coming On

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Aug 08, 2011
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Contactor
by: Anonymous

I have 240 volts on one side of the contactor in my AC condenser and 0 voltage on the other, does this mean the contactor is bad?

Aug 08, 2011
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Book
by: Anonymous

I have that book, what should I look for?

Aug 08, 2011
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Great Book
by: Dadan

this is NOT DIY site, and I really don't want a lawyer knocking on my front door.

if you're not familiar with electricity, it is not something to play with.

If you have a lot of time in your hand, there is a great book by Carrier, "hvac servicing procedures." You may find it useful.

Thanks for understanding

Dadan

Aug 08, 2011
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FAN
by: Anonymous

IS THERE ANY WAY TO BYPASS THE FAN TO IF IF THE COMPRESSOR WOULD KICK ON?

Aug 08, 2011
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5-TON AC CONDENSER UNIT
by: Anonymous

I HAVE A CARRIER 5 TON UNIT LIKE YOURS WITH THE SAME PROBLEM, HAS ANYONE COME ACROSS ANY SERVICE OR REPAIR MANUALS FOR THESE UNITS, I HAVE BEEN LOOKING, AND SINCE THEY ARE FAIRLY OLD I HAVE NOT HAD ANY LUCK YET. I HAVE BEEN ON OTHER SITES AND THINGS LIKE BAD STARTING OR RUN CAPACITOR, BAD STARTING RELAY, BURNED OUT COMPRESSOR MOTOR, BURNED OUT FAN MOTOR OR SEIZED BEARINGS ON THE FAN MOTOR, SOLENOID VALVE CLOSED, AN OPEN SWITCH, BURNED OUT CONTACTOR CONTACTS OR COIL, THE COMPRESSOR OVERLOAD OPEN OR SWITCH OPEN, ALL THESE HAVE BEEN MENTIONED AS POSSIBLE PROBLEMS. ALSO POSSIBLY LOW ON FREON, BUT IT SEEMS THESE OTHER PROBLEMS SHOULD BE ELIMINATED FIRST. DOES ANYONE KNOW HOW TO TEST FOR THESE? I HAVE DONE NOTHING TO MY CONDENSER UP TO THIS POINT, OTHER THAN CLEANING, OILING FAN MOTOR AND I HAVE CHANGED A TRANSFORMER ABOUT TWO YEARS AGO AND THE INDUCER FAN, ABOUT 15 YEARS AGO ON MY NATURAL GAS FURNACE ALONG WITH THE GENERAL MAINTENANCE FOR THE FURNACE. I WOULD LIKE TO FIX THEM RATHER THAN REPLACE THEM RIGHT NOW. THEY HAVE BEEN VERY RELIABLE UP TO THIS TIME.

Jul 29, 2011
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Fan or Capacitor
by: Anonymous

I have same unit. Either your fan motor is dead or you have a bad capacitor. The compressor won't operate unless the fan works.

Jul 18, 2011
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Where the unit wire diagram?
by: Anonymous

It would save a lot of thinking and educational guesses, if someone would provide a wire diagram of the unit.

Sincerely,

Need Pix

Jun 28, 2011
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not coming on
by: mtsflorida

Do you have a 24v electrical relay, is the thermostat getting voltage, do you have a voltmeter, does the main breaker send voltage, how about the breaker near the blower, or lastly the breaker near the big condenser fan outside?
From the drip pan runs a white pvc pipe that contain a sensor, that sometimes has water stuck inside that is preventing the system from getting power. Water must be able to drain from the drip pan or it will not work. Wires could be loose going to the thermostat from the relay. You can try to bypass the relay and send 24v straight to the themostat along the red lead or lead labeled for what is desired (i.e. heat, cold, high, low pressure) but that could cause a short, so don't even consider it.

Jun 09, 2011
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Same problem here
by: Anonymous

Did any one find the solution yet? Please let us know.

May 16, 2011
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condensate removal pump?
by: Anonymous

Could it be your condensate removal pump? When the pump breaks the condensate (Water) reservoir fills up. When it is full the outside unit will not come on and you will continue cycling your inside air through the blower. Some brands use other forms of condensate removal. This is one problem to consider.

May 13, 2011
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Re:Outside Unit Not Coming On
by: Chad

I am having the same problem. I have a Trane AC unit which is a 3or so yrs old..so basically still brand new. I just took the cover off and flipped the breaker inside the house to on. The furnace Blower goes on and stays on, but the outside unit (Fan and compressor) have not. I check all connections, and all is fine. I verified that power is coming to the outside Unit. The outside Box is fine. I even checked the wires going to the Thermostat (Honeywell) and all is fine. Same about the wires going to the Furnace.
I have Yellow, Green, White and Red between the Furnace and the Thermostat. and I have Red and White from the AC unit to the Furnace. the white from the AC Unit connected the white in the Furnace, the Red from the AC unit is connected to a slot that has the letter "C" on it, beside the "R" where the red from the Thermostat connects to.

I am hoping these wires are connected correctly.
I even opened the cover on the AC unit and check all connections, and all were fine, noting loose and all are getting power..

I never had any problems before and always turn the breaker inside off for the AC unit winter season and cover the unit.

Could this be a refrigerant problem?
is it a Thermostat issue, not sending a signal?
are the wires from the Thermostat to the Furnace and from the AC unit to the Furnace connected properly?
Do I have a bad fuse somewhere, where could it be?

Any help would be greatly appreciated

Thanks!

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Outside Unit Not Coming On

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