Question about Carrier 36KCARMS Air Conditioner

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I have a trane XE800 1991 not heat pump and I was cleaning the coils and accidently miswired the contactor when I put the fan back. The unit has a brown and a blue or wire that go to the capacitor and a black wire that does to my contactor. I put the black wire on the wrong side of the contractor. What did I fry? Compressor and fan no worky!!!

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  • shipmate7 Jun 17, 2009

    I put the wires on correctly and now nothing is working. What voltage is on the black, blue and brown fan wires.

  • shipmate7 Jun 17, 2009

    The soution was helpful



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Check for power at the disconnect and contactor on most residential units you should have 240 volts ac between the terminals and 120 volts to "ground" or "earth". Some disconnects have fuses in them. If you have circuit breakers I see little reason for fuses other than to create a service call. I usually replace them with copper tubing.
Most contactors will allow you to push them in manually (DANGER HIGH VOLTAGE). If the fan runs and the compressor does not then you have an electrical problem with the other component. There are cases where a grounded compressor or bad fan motor will cause the fan motor to run slow even though the contactor is not pulled in. A bad run capacitor will cause the compressor not to run and the same for the fan motor. Some units have a dual run capacitor that takes care of both and if it fails (it has an internal fuse) the motors will just hum (drawing high current) but not run. The compressor will have an internal overload that will disconnect the compressor after a few seconds of not starting. It will remake as soon as it cools, this condition can be mistaken as a bad compressor. Some compressor will require a "hard start kit" to solve starting problems and if it doesn't have one I recommend one as a preventative measure.
Use a clamp on ammeter to verify which parts are drawing current. If there is no current flow through the capacitors then that is a clue they may be bad.
DO NOT let your system run if the either fan motor (inside or out) is not working you will destroy your compressor, the same goes if your unit is icing up or short of charge you will burn up your compressor motor.
No control voltage: Most residential units use 24 volts ac to pull in the contactor. The power for this usually comes from a step down transformer in the furnace or indoor unit through the thermostat. Some outdoor equipment will have its own transformer, but this is rare for residential.

If the indoor blower fan wont also work then the problem is NOT the contactor in the outdoor unit but a problem with the thermostat or the wiring to it either at the subbase or the furnace. Before replacing your thermostat you should isolate the cause of the problem or it will persist and drive you nuts. Look for wires touching or cut too long.
A contactor or relay is an electrical device that takes a control signal usually 12 volts DC, 24, 120, 208-230 volts ac and creates a magnetic field to pull in a set of contacts that controls another device that may or may not get its electrical power from the same circuit. Note: 99% of most control circuits are 24 volts AC.
The contactor has steel contacts that are plated with silver. When the silver wears away you have just plain steel and the steel will weld itself together. Sometimes if you whack the contactor with a screw driver you may free it for a while but the problem will re occur. This problem is especially a problem when a piece of equipment has not been run for a period of time.
It is normal for the contactor to wear out over time like brake pads on a car. If the contactor shows any signs of wear it should be replaced as a preventative measure or as part of maintenance.
If you suspect a stuck contactor a 100% accurate test is to turn off the power to the indoor section which removes control voltage to the outdoor section and it (outdoor section) keeps running. Do not keep messing with it, your contactor it is bad and you will destroy your compressor if you let it run!!!

Some heat pump systems use two run capacitors (total of 3 if you include the fan) instead of a crankcase heater for the compressor (GE, Rheem/Ruud and others). It is possible for the contactor to fail where the compressor or the fan will run but not the other. When replacing a contactor on a system like this be extremely careful to get the wiring correct or the compressor may be damaged. so kindly check ur compressor....
both brown and blue wires as mentioned before cary 24volts
If the fan and the compressor dont run then you must have a break in a wire or a bad contactor. It also could be the run capacitor. Either way, leaving the power on could harm the compressor. It may have already. Check to see if the compressor and fan share a run capacitor. It shud be a dual capacitor that boosts the compressor and the fan. It shud read open between the common and each of the other two terminals.

good luck.....
if u found me of any help kindly rate my service.....

Posted on Jun 17, 2009


    hi this is iversha again.... please do clik on the blue links... tht is a link that explains that particular component and some issues related to that


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If you cant smell any burning smell and no fumes or smell then disconnect from the mains and put the wires back on,be careful as a capacitor holds electrical charge.Then swap the wire and if you are lucky everything is fine...

Posted on Jun 17, 2009


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I have a trane xe1200 heat pump and washed out my condenser coil.I wired it back in but I think my fan is running backwards,I feel hot air coming out of the louvers rather than from the top,is this...

Hi, you say you wired it back in? Yes it is possible for the fan to run backward if the motor is a reversible motor. And yes, if its not running in the right direction, it will not keep the head pressure down like it should. On a reversible motor, they have 4- wires at the rear normally, that you interchange to reverse it. I don't know what wires you disconnected, but unless this is a 3 phase motor which I no its not, you would have had to change those 4- reversing wires to make it run either ccw or cw. It will tell you on the motor how to do this and the rotation. The blade on the fan is positioned to scoop up the air when turning, so you can look at it and tell the direction it goes. Air is pulled through the coil and out the top, or your head pressure we stay high and cause damage to the compressor in the long run, or shut it off on high head switch. I hope this has helped you. Residential units are single phase motors that can only be reversed if made to be, and can be changed by switching those 4-wires around.
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Thermostat Wiring and Terminal Designations

Here is a list of each common terminal and what their commonly used for. Also listed is what colors are commonly used. NEVER ASSUME these are what you have. Verify all your wires by following each to each piece of equipment. This will help you to be able to match your equipment with the terminal.

- R, Rc, Rh Red wire, hot side of transformer
- C various color wires Usually the common side of transformer
- Y Yellow wire, Energizes the compressor, cooling or heating and cooling for heat pumps
- W White wire, heating for most units
- G Green wire, energizes the fan or blower relay.
- O Orange wire, energizes cooling on most heat pump units
- B Blue and sometimes Orange wire, energizes heat on most heat pump units
- B or X Blue, Black, or Brown wire, the common side of the transformer when the t-stat needs a common. Some brands use B as the common (York, GE, and Trane)
- E Pink, Gray or Tan wires, Emergency heat relay on heat pumps with auxiliary heat
- T Tan or Gray wires, For units with outdoor anticipator reset control (Trane, American Standard, GE, and Carrier)
- W2 Pink, or Brown wires energizes second stage heating on 2 stage units
- Y2 Blue or Pink wires, energizes second stage cooling on 2 stage units
- L Can be most any color, energizes service indicator lamp on units that are equipped with that.

The wires that always cause the most confusion are the B and X wires.
Check out the B terminal first. The NEMA standard for the B terminal to be the heating changeover valve but with some units it is different.

Trane, GE, York and some other manufactures which includes older Honeywell thermostats often use it for the common side of the transformer.
“X” Usually is the standard for common, but just like “B” some manufactures do use “X” or “X2” as the terminal for the emergency heat relay.

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I have a trane XR12 Heat Pump. The cooling fan on the outdoor unit does not run nor does the compressor. The fan motor heats up and hums. I am guessing that the problem is the start capacitor on the fan...

Hello Rich,NO you have a dual capasitor that runs both fan & compressor motors.Shut it down and let it cool off.You need the uf rate numbers & the volt rating of the existing cap (printed on the side)to get EXACT replacement.The wires plug in to the top termanls C, HERM &FAN.Worth fixing good luck.

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Condensor fan went out on 1999 ruud heat pump.

Did you try pushing in the contactor to see if the unit will even run?

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I have an 80,000 btu ruud furnace and a trane central air unit. the a coil keeps freezing up? there was a new blower motor put last november. and the unit has been cleaned and a new filter put in.

Hi, here are a few things that will cause a unit to ice up, and I see you have checked some, but I will go through it. Not enough air flow across the indoor evaporator coil, a dirty evaporator coil, lets say the filter had not been changed by the previous owners the dirt will cave the filter in and collect a sheet of dirt over the coil. This is the hardest coil to check and clean, but I have cleaned many of them to stop the ice build up. You say the unit has been cleaned. As far as the fan motor, it must be plugged into the high speed terminal on the circuit board in the indoor unit. This motor that was replaced should have 3- speeds. High is used for cooling and low for heating. You will see the other leads wire tied together out of the way. Colors depend on the motor for speeds, but will tell you if you are able to slide the blower out enough to see the data plate on it. White or yellow are normally L-1 or L-2, speeds are normally blue, red, and black. The wires may also be marked for what speed they are. Look on your board and you will see where the wire for the blower speed connects, it will say HI and LO. When you check these, turn it on and you can tell if the motor is running higher or lower then before. It will switch over speeds automatically to heat when its winter through the board. Motors are different in wires they use for speed colors or I could tell you, and its not the oem motor ( factory ). Blue is normally med., low is red, and high would be black, but like I say, yours may be different. Anyway, the speed, dirty coil, low on freon charge is # 1 cause. Also, make sure you don't have another filter somewhere in the home ceiling or in the retrun air stream somewhere hiding. If you were able to put a set of gauges on the unit, it would tell you right away if this coil was dirty enough to cause it to ice as the low pressure would be down to around 30 p.s.i.and a normal head. Low on freon would be a low high side and low side pressures. Check your suction line at the outdoor unit, the insulated larger of the 2-lines for ice. If you have ice there when all is melted off first, and it starts to ice there, its probably low on charge. You have a 80,000 btu furnace, but if you look at the model number on the outdoor trane, it would tell me the size of it. You will see a number such as this, 024, 030, 036, 042, 048, and 060. This will tell you the tonnage of the condenser trane unit. Here's how to figure it. There are 12,000 btu's per ton of cooling. Look at the numbers and find yours. multiply 12x2=24 a 2- ton unit, 30 a 2 1/2 ton, a 5 ton unit would be a 060. I just wanted to teach you more then anyone else will no unless they were a service tech. Why I wanted to no the tonnage is to know if the unit has a TXV ( Thermostatic Expansion Valve ) for metering freon into the coil or a fixed device. If the TXV happens to get a restriction, it will cause the indoor coil to be starved of freon and not flooded as it should be and ice up. This is rare unless at the factory when brazing a tiny piece of solder is floating around and plugged it up. I have seen this. About all that you can do on your own, is to make sure the fan is on high. The connectors at the ends will have a plastic cover over them to prevent shorts. All you need to do is unplug 1-wire and plug another in. If not sure, do each one from motor and test by hearing. You may have a door or panel switch on the perimeter that will kill power when removed. If so, tape it down to restore power. Make sure the indoor coil has no insulation stuck on it, this happens, the new blower motor is OK. The best way to de-ice a coil if you have a gas furnace is to turn on the heat! This will melt the ice off very fast so you have flow again until you find the problem. This is when you want to check the outdoor lines when all is defrosted. If it starts to ice when you turn it on, more then likely you are low on charge. I am sorry for such a long solution, I do this to try and teach the owner a little about there units and how they work. Please be kind when you rate me, this would be very good of you. I will be here if you need me. Keep me posted.
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