Tip & How-To about Heating & Cooling

Checking out a air conditioner compressor and compressor problems FIRST DISCONNECT ALL ELECTRICAL POWER Ohm the windings C to R = example 1.2 C to S = example 3.2 R to S = example 4.4 total of C to R and C to S or very close. Then ohm each terminal to ground you shouldn't get any reading If the compressor is hot or you tried to start it, the ohms will be close but not exact. No reading from C to R or C to S open winding or thermal overload. Let compressor completely cool down then ohm the C to R and C to S again If it?s an open overload, you will get an ohm reading after it cools down and the overload closes, you may just need to add refrigerant. No reading from R to S and C to S open start winding. In case of any open windings the compressor will have to be replaced. If the compressor is getting the proper voltage and won?t start, it could be locked up. You need an Ammeter to check this to see if it?s drawing locked rotor amps (60 amps or above) You also need to check the run and start capacitor. A bad run or start capacitor, the compressor won?t run, it will just hum. If the compressor will run, but quits after a while and all of the above checks out OK. It could be drawing high amps ( you will need an ammeter to check this out). Dirty condenser or condenser motor not running, overcharge of refrigerant, shunted windings, bad bearings in compressor. The compressor gets hot and Suction or big line coming in to outdoor unit is warm or slightly cool, you are low on charge or metering device bad or stopped up. If compressor runs for a while and quits and the suction line is frozen, cold or cool, then the filter, evaporator or condenser coils are dirty or plugged up, blower or fan motor not running and unit going off on high or low pressure switches.

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maytag window ac blows line cord fuse soon as turned on


Check all your electrical wires and connections. If all okay, you can remove the compressor wires and ohm the compressor motor windings to ground. If you have continuity from any winding-to-ground, your compressor is shorted out and will need to be replaced.

Apr 09, 2010 | Maytag M6Q10F2A Air Conditioner

1 Answer

compressor won't switch on, have tried reset switch and circuit breaker, but though the wall unit comes on the compressor wont..anything I can do? This has three phase power Mitsubishi..Mr Slim


If you have any experience in working with electrical systems, you can, but if not you should call a service technician.
First being very careful, check to make sure contactor is engaging.
Then check to see if you have the same voltage across all three wires on the compressor side of the contactor, assuming this is 230 volts, check T1 to T2 should have 230 volts, then check T2 to T3 should have 230 volts then check T1 to T3 should have 230 volts. If you have 230 volts to all 3 wires then the compressor is bad probably an open winding and needs replaced. Before replacing the compressor you need to check the resistance (with an ohmmeter) between all 3 terminals at the compressor. In order to do this you need to disconnect all power to the unit and ohm the compressor terminals from T1 to T2, T2 to T3 and T1 to T3 they should all have the same resistance if they do then the windings are good and the compressor is locked up, if one of the the windings is different then the windings are bad, either way the compressor needs replaced.

Nov 08, 2009 | Mitsubishi Mr. Slim MXZ30TN Air...

1 Answer

No cold air


  1. The filter could be dirty This is the most probable cause and, of course, the easiest to check and correct.
  2. The evaporator coil face could be coated with lint,dirt, etc.Dirt or lint on the coil will restrict the flow of air through the coil and the unit must be removed from the recreational vehicle and the soil must be thoroughly cleaned with strong detergent (Coil X,Calclean, etc.) and water. Be sure to protect the fan motor and electrical controls during cleaning by covering them with polyethylene sheet. After the system is cleaned, allow it to thoroughly dry for several hours (before turning it on) to prevent electrical shorts.Before system is put back into operation, be sure the filter is properly installed to prevent recurrence of dirty coil.
  3. No compressor (Does not try to start).The compressor does not run and it does not hum.
    1.The selector switch may be open.
    2. Thermostat may be open.
    3. Overload switch may be open.
    4. Compressor winding may be open.
  4. Selector Switch
  5. Thermostat
  6. Low Voltage
  7. Overload
  8. Compressor
  9. Wiring (Mis-wired)
  10. PTCR or Potential Relay
  11. Start Capacitor
  12. Run Capacitor
To check the selector switch, remove wires from the terminals
and rotate the switch to the proper position and read
continuity as follows:
Terminals Switch Position
L-1-3 Lo Heat
L-1 Lo Fan
L-2 Hi Fan
L-1-4 Lo Cool
L-2-4 Hi Cool


Compressor Motor
The compressor motor is located inside the hermetic
compressor housing and therefore not accessible for service or
visual observation in the field. However, the motor winding
condition can be analyzed by using an ohm meter. Be sure to
remove all the leads from the compressor terminals before
making this check.
1) If the resistance between any two terminals is 0
ohms, the motor windings are shorted.
2) If the resistance between any terminal and the
compressor housing is anything but infinity, the
winding is grounded.
3) If the resistance between any two terminals is
infinity, the winding is open.
On a good compressor, the highest resistance will be between
the R (run) and S (start) terminals. The lowest resistance will
be between the C (common) and R (run) terminals. The
intermediate resistance will be between the C (common) and
S (start) terminals. Notice that compressors have the
identification of the terminals marked on either the terminal
cover or on the compressor housing.

Capacitor Check
There are several capacitor test devices available. The ohm
meter is one of them. The ohm meter cannot verify a
capacitors MFD (microfarrad) value. However, the following
procedures will show you how to use an ohm meter to
determine if the capacitor is good, open, shorted or grounded.
Before testing any capacitor, always perform the following
procedure:
* This test must be done with a analog type meter.
a) Disconnect all electrical power to the air conditioner.
b) Discharge the capacitor with a 20,000 ohm (approx.
3 watt) resistor or larger.
c) You may discharge capacitors with a standard volt
meter if you use a scale over 500 volts and touch the
leads (one lead to each side of the capacitor). The
volt meter will discharge the capacitor.
d) Identify and disconnect the wiring from the
capacitor.
e) Set and zero the ohm meter on the “highest” scale.
When testing for a good, open or shorted capacitor,
perform the following checks: Place the ohm meter
leads across the capacitor terminals (one lead on
each terminal) and perform a continuity test. Then
observe the action of the meter needle or indicator.
Reverse the leads and test again. The result should
be the same. Note: If the capacitor had not been
properly discharged, a false reading could be
indicated on the first test. Always test several times
(reversing the leads with each test). This will verify
the capacitors condition.
Good Capacitor
If the capacitor is good, the indicator will move from infinity
(the left side), towards zero ohms and slowly return back to
infinity. Reverse the leads and test again. The result should
be the same.

Start Capacitor
Most models use a start capacitor and a start relay to give the
compressor high starting torque. The compressor will,
therefore, start against normal pressure difference (head
pressure minus suction pressure) even when shut down for a
short period of time. The start relay will disconnect the start
capacitor when the motor reaches approximately 75%
running speed.
Start (Potential) Relay
The start relay consists of –
1) Normally closed contacts internally between
terminals #1 and #2 which switch in the start
capacitor in parallel to the run capacitor during shut
down and then switch out the start capacitor when
the motor reaches approximately 75% normal
running speed.
2) A high voltage coil internally between terminals #5
and #2 to actuate the contacts. The coil is too weak
on line voltage to actuate the contacts, but it is
connected in series with the start winding and it gets
the generated voltage of the start winding portion of
the compressor motor. This generated voltage is
much higher than line voltage and varies with the
speed of the motor. Therefore, since the relay is
designed to open the contacts at 75% of normal
running voltage (measured between terminals #5 and
#2), the contacts will open (thus disconnect the start
capacitor) at approximately 75% of normal running
speed.
(B) Positive Temperature Coefficient Resistor
(Commonly Known As PTCR Start
Device)
The resistor acts like a potential relay in that it takes the start
capacitor out of the start circuit, but uses resistance of
electrical flow (back EMF from compressor) instead of
opening a set of contacts. The service person should be careful
handling the resistors. They will be hot during operation (up
to 160 degrees F). The air conditioner needs to be off for 3-5
minutes during cycle time and when servicing to let the
resistor cool down.

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That covers everthing.
Please rate this a fixya

Feb 09, 2009 | Coleman Mach III Air Conditioner

1 Answer

Haier AC Problem Troubleshoot.


Your compressor is faulty, you could test this with an ohm meter or a mega tester to confirm that you have continuity between windings and earth or that the insulation on one of the start or run windings has overheated and broken down. Before you give up though, you can try to change the compressor capacitor, with same rated microfarad capacitor.

Jan 16, 2009 | Haier hwr10xc6 Air Conditioner

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