Oshkosh Corporation Classification ‐ Restricted
Title:

MCC HVAC Upgrades

Number:

SB_588

Release Date:

6/20/2022

Revision Number:

n/a

Revision Date:

n/a

Chassis Type:

Velocity, Impel, Enforcer

Component
Description:

MCC HVAC SYSTEM

Warranty:

Parts and 2 hours’ labor are covered under the 1-year Basic Apparatus warranty or the 3 year
Velocity/Impel chassis warranty (where applicable). Not covered outside of the 1-year Basic
Apparatus or 3 year chassis warranty *This is NOT A CAMPAIGN or RECALL. All claims subject to
terms & conditions per customer Service Policy & Procedure Manual

Parts:

N/A

Tools:

N/A

Subject:
Addressing fault codes and upgrades to the MCC HVAC system.

Purpose/Background:
1. When to update MCC HVAC control panel software (programming kit vs updated control panel part #)
2. Allowing temperature control while in defrost mode
3. Correction to unbalanced air flow out of the evaporator
4. CZ programming to fix the high and low side pressure readings from flashing in CZ Live Data screen
5. CZ programming to change HVAC SPN faults from #’s to verbiage
6. Supply HVAC fault code list for dealer reference

Description:
The MCC HVAC Control Panel has an internal software which allows for the HVAC system to broadcast pressure
readings, PWM signals along with faults that are internal to the system. What we have learned of the early
software in the control panel, is that it will broadcast these faults to our Command Zone system even when the
HVAC system is not active. Therefore, we have worked with the manufacturer of the control panel and have come
up with new software to program into the earlier versions to broadcast faults when the system is active.
There are 2 types of fault categories we are looking to eliminate from being displayed:
1. Any time messages
a. LIN communication loss
b. Air return sensor out of range, or
c. After coil temp sensor out of range
2. Messages only sent when the AC system is intended to be engaged
a. High and low pressure issues
b. Anti-icing sensor out of range
c. Air conditioner stopped due to issue
This will eliminate unnecessary messages and only display the faults that are currently active which will save time
on troubleshooting and part replacements. The upgrade also allows the temperature to be controlled in defrost
mode. To ensure that the AC system operates correctly and doesn’t spray condensation through the vents, an
internal baffle needs to be added to the diffuser as part of the air balancing package that also increased fan
speed.
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Procedure:
If it is determined that the control panel requires the updated software, please start a Technical Incident and you
will be advised what below option is best suited for the vehicle.
1. Control panel part number # 63-4753-0001.
a. This panel is the current, production version from HED with 7.06 software installed
2. Control panel part number # 4067788.
a. This panel is a refurbished part. A previously installed controller that has been updated to the
current software 7.06.
3. MCC programming kit part number # 4022115.
a. This allows dealers to program the current control panel on the vehicle with 7.06 software.
Dealers can hold on to these programming kits to update other vehicles in their area, if required.
b. Dealers will be refunded the cost of the kit when returned to Pierce Aftermarket Product Support
c.

If the programming is determined as the best option, the technical team will process the order.
When we process the kit, we will send out the programming instructions and software at that time

When the new software is installed, make sure the diffuser kit has been installed in the back of the evaporator. If it
is not installed, please order kit # 4067393 through Pierce’s parts team. Please see reference print 4021455 for
installation instructions.

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MCC HVAC Fault Codes:
LIN MODULE COMM LOSS

Amber

519169

31

0xC3

LIN MODULE COMM

Amber

519169

31

0xFE

HIGH SIDE PRESS SENS ISSUE

Amber

519170

31

0xFE

HVAC HIGH PRESS SENS ISSUE

Amber

519170

31

0xC3

HVAC LOW PRESS SENS ISSUE

Amber

519171

31

0xC3

HVAC LOW PRESS SENS ISSUE

Amber

519171

31

0xFE

Amber

519172

31

0xC3

Amber

519172

31

0xFE

AFTER COIL TEMP SNSR OUT
RANGE

Amber

519173

31

0xC3

AFTER COIL TEMP SNSR OUT
RANGE

Amber

519173

31

0xFE

ANTI ICE SENSER OUT OF RANGE

Amber

519174

31

0xC3

ANTI ICE SENSER OUT OF RANGE

Amber

519174

31

0xFE

EO HIGH SIDE PRESS TRANS
ISSUE

Amber

519175

31

0xFE

HVAC LOW PRESS SENS ISSUE

Amber

519176

31

0xC3

CAB TEMP SENSOR OUT OF
RANGE
CAB TEMP SENSOR OUT OF
RANGE

There are no LIN modules connected to HVAC
dash panel.
There are no LIN modules connected to the
HVAC dash panel.
The high side (discharge) pressure transducer
is reading a value out of normal operation
range.
The high side (discharge) pressure transducer
is reading a value out of normal operation
range
The low side (suction) pressure transducer is
reading a value out of normal operation range.
The low side (suction) pressure transducer is
reading a value out of normal operation range.
The cab air temperature sensor is reading a
value out of the normal operation range.
The cab air temperature sensor is reading a
value out of the normal operation range.
The overhead after coil temperature sensor is
reading a value out of the normal operation
range.
The overhead after coil temperature sensor is
reading a value out of the normal operation
range.
The air condition anti-icing temperature sensor
is reading a value out of the normal operation
range.
The air condition anti-icing temperature sensor
is reading a value out of the normal operation
range.
The engine off high side (discharge) pressure
transducer is reading a value out of normal
operation range.
The engine off low side (suction) pressure
transducer is reading a value out of normal
operation range.

Troubleshooting Common Issues:
1. Engine Off High/Low Side Pressure Transducer Issue Faults and HVAC High/Low Pressure Sensor Issue
Faults
a. Are codes present with system off?
i. Yes - update software in control panel or order new panel as stated in above procedure
ii. No - go to step B
b. Unplug transducers and see if AC turns on
c.

If system activates, then recover refrigerant

d. Charge refrigerant to appropriate charge in table below:
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e. After the vehicle is properly charged, do codes go away?
i. Yes - no other checks are needed
ii. No - replace transducers (if only a high side fault-replace just high side transducer
f.

Last step is to look at charge written on the data placard to ensure it shows the correct refrigerant
charge

g. Order data tag if incorrect charge is on data placard

2. Anti-Ice and After Coil Temp Sensor Out of Range Faults
a. Are codes present with system off?
i. Yes-update software in control panel or order new panel as stated in above procedure
ii. No-go to step B
b. Inspect sensor and sensor wiring (pins 11 and 12 out of LIN Module and common ground from
pin 4 of 4 place connector for evaporator)
c.

If sensors and connections look good, please start technical incident with Pierce technical team to
be advised on part replacement

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3. Flashing pressure readings in Command Zone display
a. Flashing high and low side pressure values have been reported while monitoring the readings in
the live data page on the Command Zone Display
b. Flashing values can cause the AC system to not activate
i. Start technical incident to have CZ programming completed to correct values from
flashing
4. MCC HVAC fault codes display as SPN numbers
a. Fault codes that are broadcasted from the control panel to the Command Zone display can show
as SPN and FMI numbers
b. We would like to have these programmed, so it is correct to come up as verbiage to help assist
our customers and dealers when diagnosing
i. Start technical incident to have Command Zone programming completed
5.

AC System Does Not Activate
a. Are there fault codes present?
i. YES
1. See above if they are related to issue 1 or 2
2. If they are Lin module comm loss or temp sensor faults, please start a technical
incident for assistance
ii. NO
1. Refer to chassis AC print and verify control panel has a good IGN source (12
VDC) at pin 1, 5-volt reference on pin 2 and a good ground on pin 3
a. Repair if not present
2. Inspect AC on signal out of control to ensure it has 12 VDC going to Evaporator
(ckt 3413, pin 5 of controller to pin 2 of 6-place connector on evaporator)
a. If not present out of controller, please start technical incident
3. Check to ensure 3413 is present at the thermostat module inside the evaporator.
If this is present the thermostat module will then send out a signal on ckt 1395 to
the binary high-low pressure switch
a. If 12 VDC are present on ckt 3413 “AC on Signal” to the thermostat
module, but no voltage on ckt 1395 “comp clutch” then it is likely there is
not enough load to indicate that the thermostat module does not have an
open circuit.
b. If 12 VDC are not present, then please start a technical incident. The
thermostat will most likely have to be replaced with one that has a
resistor built in to supply a large enough load or a module with the open
circuit check removed
4. Pressure switch will close and allow the signal to go to the compressor on/off
relay

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6. Digital Temperature Displayed in Wrong Format
a. Temperature can be displayed in Fahrenheit or in Celsius
i. To change one from the other, press the center AC button quickly 6 times and wait 10-15
seconds for it to change
ii. It might be required to wait and press the AC button one more time for it to change over

AC Button

7. Evaporator Fans Slow Down or Will Not Run
a. Ensure faults are not active and not in a load manage state
b. Mechanical siren cable needs to be ran back and connected to the battery. It can be connected
direct or switched battery. We just need to eliminate it from the passenger side cab distribution as
it requires such a high amp draw at start up and operation
c.

If condition continues after siren cable reroute, then wires (ckts 1397 and 1398) for the evaporator
need to have the wire size increased to 8 awg. This will be run from the evaporator fan fuses in
the cab roof distribution all the way to the evaporator fans.

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Reference Print 401455

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