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My acworks fine when i switch to heat blower comes on but heat doesnt also no 24 volts on contactor in heat

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Is this an electric furnace using heating strips as the heat source?
Or is it a heat pump system?

Posted on Dec 02, 2014


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Posted on Jan 02, 2017

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SOURCE: Carrier AC Compressor Fan will not turn on.

Bad contactor - replace

Posted on May 07, 2009

  • 146 Answers

SOURCE: i have a split system air conditioner. the inside

contactor working means fan might be bad can you feel any resistance from fan or bad capacitor.

Posted on Jun 24, 2009

  • 26 Answers

SOURCE: I replaced the contactor and the unit still doesn't work

Are you getting 24 volts at the contactor coil? If not check your control voltage wiring to the unit. If all is good check refrigerant charge, you will need gauges for this, compressor can be held out due to low pressure, also unit can be out by the high pressure safety switch which is normally reset manually.

Posted on Jul 14, 2009

  • 86 Answers

SOURCE: Blown Transformer heat pump

blown transformers are usually from a low voltage short the first thing i would do is wire a automotive or resetable 3amp fuse in line with the transformer so you dont blow transformer after transformer the wire coming off the transformer that say 24v take that wire a couple of inches down and cut it and install the fuse in series there

now you can go through your low voltage wires one by one and test them unhook all the wires to your outdoor condenser at your indoor unit(furnace or airhandler) and try turning it to cool now if you blow the fuse the short is between the tstat and the indoor unit if the fuse is still good leave it on cool and hook up one wire at a time to your outdoor unit starting with R a lot of times your contactor or your defrost board will short out on you also look for pinches in wires wires with cracks in the insulation and wires touching metal this situation can be a real pain sometimes i would recommend calling a hvac company if you start to get stumped
hope this will help you

Posted on Jul 26, 2009

  • 674 Answers

SOURCE: contactor not pulling in on 24 volts after

Set the thermostat so that the a/c should be on. Make sure you have 24vac at the contactor. If you don't recheck your wiring. Also you can go to the thermostat and install a jumper between R and Y. The contactor should pull in. If it does, your thermostat may be the problem. Let me know what you find so I can offer more advice.

Posted on Aug 06, 2010

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I have a Arctic King through wall AC model MWW-12ERN1-MI0 and the compressor will not engage to cool the air. Can anyone help me diagnose and fix this problem?

On the ac unit electric section, check for power at Y1, should have power, possibly to x or c ( common terminal).
Check for power across the compressor contactor, should have power or something is open such as a pressure switch or compressor protection. If there is control power at compressor contactor solenoid ( 24 volts control), then check for supply power on line side of contactor, then on load side of contactor (supply voltage e. g. 230 volts. If all voltages are present, then check the compressor for opens and electric continuity.
CAUTION: electricity is dangerous, can kill and/ or cause fires. Do not attempt if not aware of safety procedures.

Aug 08, 2017 | Heating & Cooling

1 Answer

Why won't the compressor run

This can be for a variety of reasons. It ranges from something as simple as no supply power (blown fuse, open breaker, faulty contactor, or run capacitor) or it could be more serious as a grounded or open winding in the compressor motor. My suggestion to any novice and or person without proper tools and knowledge; First check the low voltage (24 volt control voltage) by turning on the "Fan on" switch located on the thermostat to on, not "Auto" The blower fan should come on, indicating there's 120 volt and 24 volt available. Fan doesn't come on is an indication that there's no control power. The next step would be to check for power at the transformer and fuse located in the air handler. There should be 240 volts feeding the transformer, and 24 volts coming out. The control voltage is needed to operate the thermostat (which is the switch that sends the 24 volt signal to the compressor contactor to turn the compressor on/off. This 24 volt also powers other relays and switches in the system. knowing that 24 volt is available also tells you that the problem is most likely in the condensing unit (outside, where the compressor is located). At the condensing unit you should check for 240 volt supply power. Upon finding 240 volt supply power the question now becomes whether or not the thermostat is calling for anything (cool or heat if the unit is a heat pump). There should be 24-30 volt available at the small gauge wires feeding the contactor coil. While having the thermostat set at a temperature lower than the current room temperature (in the cooling mode) the thermostat should send a 24 volt signal to close the compressor contactor and turn it on. The non-metallic end of a screwdriver can be used to depress the moveable part of the contactor. After pushing in the contactor, should the compressor start then you may only need a new contactor. It may just hum because of a faulty run capacitor or grounded or shorted internal motor windings (grounded or shorted windings are usually indicated by tripped circuit breaker and/or blown fuse). It's a good idea to have a good multi-meter and knowledge of use before attempting any repairs or diagnosis on your own. I recommend some basic knowledge of electricity before even thinking about attempting any repairs or diagnosis.

May 08, 2014 | Goodman Manufacturing Goodman GSC130421...

1 Answer

A/c blower comes on but outside unit does not

do you have power to the outside unit. If so you may have a bad contactor or loose 24 v control wiring

Apr 23, 2014 | Ruud Rheem Weather King 24 Volt Contactor...

1 Answer

Cool will not come on when it's set in auto mode

A thermostat is only a switch, nothing more. It's job is to cut on and off the cooling/heating equipment based on a preset temperature setting. It sends 24-28 volts to a contactor or relay which does the actual closing (turn on) or opening (turn off) the power to the compressor or furnace, and that's all it does. There could be a problem with the other parts of the system. When the space temperature exceeds the preset temperature the thermostat should provide 24-28 volts to the compressor contactor, to start the compressor. The "Auto-on" switch on the thermostat controls the fan only. If there isn't 24-28 volts from the thermostat to the coil of the contactor, the compressor will not operate,

Oct 30, 2013 | Hunter Fan Company 42999B - Heat/Cool...

1 Answer

Electrical diagram for contactor (240 v/1 phase/24 v coil)

How to connect motor 1 phase with mcb , contactor , timer ,switch selector on off on , and lamp indicator

Feb 17, 2012 | Omega Trane Furnace Draft Inducer Blower...

2 Answers

Model UAKA 030JAZ was working fine. Now, the compressor fan does not come on and neither does the compressor. I don't know how the contactor works but it is not engaging (the spring loaded contacts are...

You need to complete the 24 volt circut from the themostat to the transformer to get the contactor to pull in.

Check for voltage at the transformer,should be 120 v in 24 volts out.Also there may be a small reset button on the transformer.

Apr 18, 2011 | Ruud UAKA030 Air Conditioner

1 Answer

I have an old Miller 3 ton heat pump. It will work fine sometimes but when it decides not to work i can go outside and press the power contactor and the unit will come on as long as i hold the contactor...

it sounds to me you need just a really good tune up maybe a new contactor retest your low voltage what do you have from common to 24 volts it should be 27 volts if you test each wire you want get 24 v it will be like 7 or so

Sep 22, 2010 | Heating & Cooling

1 Answer

No heat or cool on my payne heat pump

If you can manually push in on the contactor and the fan runs, your not getting 24 volts across the contactor coil.
If the contactor is not energized, your compressor want be running, the contactor controls the fan and compressor.
You need to measure the voltage across the contactor coil and if you don't have 24 volts then you need to either jumper the pressure swiches or measure the voltage across the pressure switches if you read 24 volts then they are open.
If low pressure switch is open you are probably low on refrigerant, if high pressure switch is open it's bad.
If these check out ok then you might check the low voltage wires for loose connections or the wires from unit back to house and under the house to see if there's any breaks or insulation chewed up from lawn mower or animals.

Jan 09, 2010 | Heating & Cooling

3 Answers

Replace Contactor Relay on Rheem Air Condenser

I have a Rheem heat pump/airconditioner, Mod # RPFA-036JAS, that I have had problems with for at least 5 years and have paid over $1,000 in parts and service calls. I can vever recreate the problem when a tech is here. It usually happens in the middle of the night. I hear a Click, ckick, click sound, through the unit and it sounds like it is comming out of my air handler, but the outside unit also clicks at the contactor and the condensor cooling fan moter will start and stop about every half secongd or second. Both contactors have been replaced, the small one twice, one capaciter
has been replaced. I allow the unit too cool down and its alright for a few hours. That is difficult when the outside temp is below zero. HELP PLEASE!

Feb 16, 2009 | Heating & Cooling

1 Answer

No heat , out door unit doesn't run?

turn fan switch at stat to on . does fan run? it should within 2 to 3 minutes if not sooner. if it does then you know you have low voltage and high voltage a blower and electronic brain . go outside and see of you hear a hum like a faint buzz. that is the contactor being closed and energized. check to see if outdoor disconnect has power ,usually 220 volts and then remove service panel and see if 220 volts arrives at contactor. see if spring loaded contactor points are pulled in and check to see if voltage is feeding through contactor . this will be hot! be sure you know how to use a meter and work live power. if contactor is not pulled in then you have a control voltage problem and you have to get 24 volts from stat to indoor blower to outdoor condensor. with and insulated screwdriver you can simply mash in on the contactor points and fan and compressor should run . only do this for a second or two, but it does simply say hey contactors open, ive got power and it will run but no controll volytage.IF ITS A RUUD OR A RHEEM SOME OF THEM HAVE A RESET BUTTON DOWN WHERE THE REF LINES GO IN . MASH IT IN AND IT MAY RESET, THEYTRIP OFF HIGH PRESSURE, DIRTY FILTER OR COIL IN HEAT OR A BAD FAN MOTOR OUTSIDE IN COOL.

Oct 09, 2008 | Goodman Heating & Cooling

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