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TECHNICALLY By
Ed Brink, Meier Supply Training and Technical Specialist |
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2010 Issue1
Meier Supply Co., Inc., 123 Brown Street, Johnson City, NY 13790
www.MeierSupply.com EBrink@MeierSupply.com 607-797-7700
INSIDE THIS ISSUE
1 Secrets of Mitsubishi P- Series Fault Codes
P Series Maintenance Tool
3 List of Mr. Slim fault codes
Unlocking the Secrets of Mitsubishi P Series Fault
Codes
Let’s talk about fault codes. One of the
most frustrating things for a technician is coming across a piece of equipment
that is flashing a fault code and not having any idea as to what that code is
telling them. Manufacturers use fault
codes and flow charts to help guide the technician in troubleshooting equipment
failure. With the implementation of electronics and CPUs in HVAC equipment,
more and more HVAC manufacturers are designing equipment that is capable of performing
self-diagnostics and if a problem exists, display a fault code that is
associated with it. In order for the technician to effectively troubleshoot the
equipment, they need to decipher the code and interpret its meaning. Without
this information the technician is at a disadvantage during the troubleshooting
process.
This article will focus on how to retrieve fault codes and the use of
manufacturer’s flow charts for the most common fault codes associated with
Mitsubishi P series ductless splits. I will also review some common test
procedures that can be used to aid in the troubleshooting process and how the P
Series maintenance tool (part# PAC-SK52ST) is an important device that can save
the technician valuable time.
In order for any piece of equipment to operate properly it must be supplied
with the correct voltage and wired properly. Line voltage is wired to the
outdoor unit and power to the indoor unit is supplied from the outdoor unit
using 16 or 14 gauge stranded wire (not thermostat wire). If a means of
disconnect is needed at the indoor unit it is recommended that the TAZ-MS303 3
pole switch be used. Refer to the wiring diagram or the technical service
manual (found at http://www.mrslim.com/customerCare/resources.asp) of the
specific model to determine proper wiring location and expected voltage
readings at those locations.
Power is supplied to the outdoor unit at L1 & L2. Power is supplied to
the indoor unit from the outdoor unit on terminals S1, S2, & S3. Terminals S1 & S2 are the line voltage
power supply wires to the indoor unit and should measure a voltage between them
of 208-240 volts A/C. Each leg should
have a voltage of 110-120 volts A/C to ground.
Terminals S2 &S3 are the communication wiring between the indoor and
outdoor PC boards and should measure a fluctuating voltage of 12–24 volts DC.
Verifying these voltages is the first step in the troubleshooting process.
The next step is to retrieve the fault code from the unit. There
are several ways to do this depending on the type of controller being
used. Refer to the technical service
manual (found at http://www.mrslim.com/customerCare/resources.asp) for the
proper procedure associated with the type of controller used. If the technician
has the P series maintenance tool and the outdoor unit is compatible with the
maintenance tool, the technician can simply plug the maintenance tool onto the
outdoor circuit board at terminal CMN to retrieve the fault code. Codes are
displayed on the maintenance tool using 2, 7 segment led’s (example P-8). Fault
codes will have a prefix of: P, F, U, Fb or E.
Let’s take a
look at them individually: P1-P9 & Fb indicate a malfunction of the
indoor unit, U1-UP & F3-F9 indicate a malfunction of the outdoor unit,
E0-E5 indicate a remote control transmission error and fault codes of E6-EF
indicate indoor/outdoor communication errors.
Once the fault code is retrieved the technician can start the
troubleshooting process. He must determine what the fault code is telling him
by using the appropriate charts to decipher its meaning. Then he can use the
appropriate flow chart to find the root cause.
Here is an example using a U1 fault and a PUZ-A24 outdoor unit. The unit
will not run. The fault code needs to be retrieved. This can be done in one of
three ways. If the system uses the PAR 21 wired controller the fault code of U1
will be displayed on the controller’s screen. If using the maintenance tool
the fault code of U1 will be displayed on the
screen that was retrieved from the outdoor circuit board. If the system uses a
wireless controller the fault code is retrieved using the malfunction-diagnosis
procedure of the wireless control. When this information is recalled there
would be 6 beeps with an output pattern of B that corresponds to a U1 fault
(remember to refer to the technical service manual for the proper procedure
associated with the type of controller used).
Next we need to use the troubleshooting section of the technical
service manual for the PUZ outdoor manual to look up the meaning of the U1
fault code (Found on page 37). It states that a U1 fault code is caused by the
high pressure switch opening during compressor operation. The technical service
manual also gives a flow chart for determining the root cause of the problem.
With this information we have the necessary information needed to effectively
troubleshoot this fault. As you can see, the code is useless unless we are able
to interpret its meaning using the appropriate technical service manual.
As the HVAC industry changes and equipment becomes more intelligent, we as
technicians need to stay a step ahead and arm ourselves with the tools
necessary to make our jobs easier. Our tool boxes are going to look less
traditional as time goes on. Service manuals, diagnostic tools and laptops are
going to be as commonplace as a screw driver or pump pliers. We not only need
to be able to collect information but we must be able to interpret it.
Mitsubishi has all of this information easily obtainable with the P series
service tool. There are over 50 pieces of valuable information that can be
obtained using this tool. In addition to retrieving fault codes, this tool
enables you to see what the circuit board is reading as operating conditions.
Here are a few examples: compressor
operating current, LEV position, all sensor readings, DC bus voltage,
compressor frequency, superheat and sub-cooling reading can be obtained using
this tool. Once you have this information you can retrieve the technical
service manual from: http://www.mrslim.com/customerCare/resources.asp or use
the attached flow chart to aid in servicing the most common fault codes
associated with the P series product line.
The final topic is the power up process for Mitsubishi P series equipment
with individual service switches at the indoor and outdoor units. In order to
place the equipment in service after a repair or to properly clear any faults
the equipment needs to be powered up in the proper procedure. If this procedure
is not followed correctly the unit may go into a communications fault. After the entire system has been powered off
for a minimum of five minutes, apply power to the indoor unit first, then the
outdoor unit. The communication signal
is sent from the outdoor unit and if the process is reversed the outdoor unit
may not receive a signal from the indoor unit in the proper amount of time
causing the unit to go into a fault.
If you have any questions, please
contact:
Ed Brink, Meier Supply Technical and
Training Specialist
Meier Supply Co., Inc.
123 Brown Street
Johnson City, NY 13790
email: EBrink@MeierSupply.com
phone: 607-797-7700