Title:

MCC HVAC Upgrades

Number:

SB_588.4

Release Date:

6/20/2022

Revision Number:

4

Revision Date:

7/25/2023

Chassis Type:

Velocity, Impel, Enforcer

Component
Description:

MCC HVAC SYSTEM

Warranty:

N/A

Parts:

N/A

Tools:

N/A

Subject:
Addressing f ault codes and upgrades to the Midwest Climate Control (MCC) HVAC system.
Purpose/Background:
1. When to update MCC HVAC control panel sof tware (programming kit vs updated control panel part #)
2. Allowing temperature control while in def rost mode.
3. Correction to unbalanced air f low out of the evaporator.
4. CZ programming to f ix the high and low side pressure readings f rom f lashing in CZ Live Data screen.
5. CZ programming to change HVAC SPN f aults f rom #’s to verbiage.
6. Supply HVAC f ault code list f or dealer ref erence

Description:
The MCC HVAC Control Panel has an internal software which allows for the HVAC system to broadcast pressure
readings, PWM signals along with f aults that are internal to the system. What we have learned of the early
sof tware 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 sof tware to program into the earlier versions to broadcast f aults when the system is active.
There are 2 types of f ault categories we are looking to eliminate f rom being displayed:
1. Any time messages.
a. LIN communication loss
b. Air return sensor out of range
c. Af ter 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.

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SERVICE BULLETIN #SB_588.4
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 def rost
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 dif f user as part of the air balancing package that also increased f an
speed.
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 f or the vehicle.
1. Control panel part number # 63-4753-0002.
a. This panel is the current, production version f rom HED with 7.10 sof tware installed.
2. Control panel part number # 4231502.
a. This panel is a ref urbished part. A previously installed controller that has been updated to the
current sof tware 7.10.
3. MCC programming kit part number # 4022115.
a. This allows dealers to program the current control panel on the vehicle with 7.06 sof tware.
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.
4. If vehicle is hardwired (not using multiplex networking) re-pin load manager connector to control panel
part number # 63-4753-0002.
NOTE: Do not re-pin connector if the vehicle matches the table below:
Chassis

Wire Harness Part Number

Description

Velocity

64-3407-H011

Wire Harness, Cab, Inst, Panel

Enf orcer

64-3407-H011

Wire Harness, Cab, Inst, Panel

a. With the correct Mini-Fit Junior pinning tool, re-pin wire 3495 in connector C184 from pin 16 to pin
14.
b. If the correct Mini-Fit Junior pinning tool is not available:
i. Cut wire 3495 at connector C184.
ii. Connect wire 3495 to wire 4562 at connector C309.
iii. Leave wire 4562 in connector C184 pin 14.
c. Ref er to diagram below:

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SERVICE BULLETIN #SB_588.4

When the new sof tware 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 f or
installation instructions.

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SERVICE BULLETIN #SB_588.4

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 of f ?
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 ref rigerant.
d. Charge ref rigerant to appropriate charge in table below:
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e. Af ter 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 f ault-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 Af ter Coil Temp Sensor Out of Range Faults
a. Are codes present with system of f ?
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 f rom
pin 4 of 4 place connector f or 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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SERVICE BULLETIN #SB_588.4
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 f rom
f lashing.
4. MCC HVAC f ault 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 f ault 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 f or assistance.
ii. NO
1. Ref er to chassis AC print and verif y control panel has a good IGN source (12
VDC) at pin 1, 5-volt ref erence 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/of f
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 f or 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 f aults 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) f or the evaporator
need to have the wire size increased to 8 awg. This will be run f rom the evaporator f an f uses in
the cab roof distribution all the way to the evaporator f ans.
8. Low Air Flow out of the Rear Vents
a. If there is a significant notice in decreased air flow in the rear of the evaporator compared to the
f ront, we need to inspect and cover the recessed compartment where the LIN Module is mounted.
b. Creating a f ab part to mount over the compartment has significantly increased the air f low in the
rear.

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SERVICE BULLETIN #SB_588.4
Reference Print 401455

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