IK1900198 - MaxxPower No Idle Battery-Powered A/C System Diagnostic Guide.

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Countries:

UNITED STATES

Availability:

ISIS, Bus ISIS, FleetISIS Revision:

Document ID: IK1900198

Major System:

ACCESSORIES

8

Created:

7/23/2012

Current Language: English

Last Modified: 6/4/2014

Other Languages: NONE

Author:

Viewed:

Will (Mark) Wiley

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Title : MaxxPower No Idle Battery-Powered A/C System Diagnostic Guide.
Applies To : Feature code 16UZL

Home

Table of Contents

Additional Resources

Basic Troubleshooting

Component Identification and Location

Diagnostics Table

Appendix

Circuit Diagrams

Photos with Call Outs

Parts Information

SRT Information

Change Log
If this iKNow Article is being revised, please type in the text box what has changed in the article. The change log is meant for Dealers to be able to see what
has updated/changed in the article.
Changed:
5/21/2014 - Updated "Parts Information" section to include new harness part numbers. Added SRT Information and links.

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

Description
Diagnostic guide for the MaxxPower A/C system.
• For the A/C side, only a few electrical components can be replaced.
• DO NOT REPLACE THE COMPLETE UNIT IF THE A/C IS NOT FUNTIONING.
• Refer to the BASIC TROUBLESHOOTING below prior to replacing any components. This will help you identify which component is at fault or any
electrical issues.
• Refer to PARTS INFORMATION to properly identify the parts that may require replacement
• The A/C portion of the system is listed below in the parts section.
• The 16UZL No-Idle HVAC system is designed to disengage when the engine is started, and can be turned on with the key in any position.
This battery-powered no idle HVAC system provides heating and cooling of the sleeper area without use of the vehicle engine.
The system is comprised of the no idle HVAC components located in the sleeper HVAC module, a separate fuel operated coolant heater mounted under the
sleeper, and four additional batteries housed in a second battery box. The no idle HVAC system shares the air handling assembly and several major
components with the truck's standard HVAC system. Most importantly, the shared evaporator core contains refrigerant circuits for both the no idle system and
the truck's standard A/C system. With this configuration, some procedures required to service the no idle A/C system will require opening the refrigerant circuit
of the truck's standard A/C system.
Trucks equipped with 16UZL No-Idle HVAC system have two separate HVAC systems (Standard Truck A/C and the MaxxPower unit), it is important
to identify each clearly, so you are troubleshooting the correct system.

Per the Operators Manual page 10: Run the heater at least once a month during the year (for a minimum of 15 minutes).
TABLE OF CONTENTS
Use the menu bar at the top of the screen to navigate through the topics listed.
• Basic Troubleshooting
• Component Identification and Location
A: Compressor Fuse 60 Amp (Maxi)
B: System Controller Fuse 10 amp (Mini)
C: Blower Fuse 20 amp (Mini
D: Condenser Fan Fuse 20 amp (Mini)
E: Relays (Compressor, Condenser Fan, Blower)
F: Fan and Temperature Control Display
G: System Controller
H Compressor Controller
I: Linear Power Module
J: Blend Door Actuator
K: Inlet Temperature Air Sensor
L: Discharge Temperature Sensor
M: Evaporator Blower
N: Condenser Fan

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O: High Pressure Switch
P: Compressor
Q: Thermal Limit Switch – Compressor
R: Evaporator Inlet Filter
• Diagnostics Table
• Appendix
A: Batteries
B: LED Control Display Testing
C: Relay Testing
D: Pressure Switch Testing
E: Fuses
F: Discharge Temperature Sensor/Freeze Switch Testing
G: Inlet Temperature Sensor
H: Blend Door Actuator
I: Compressor Thermal Limit Switch
J: System Controller
K: Compressor Controller
L: Condenser Fan Testing
M: Evaporator Blower/Linear Power Module Testing
N: Compressor Rubber Mount
O: Discharge Sensor and Air Inlet Sensor Chart
P: Navistar Fault Codes Chart
Q: Pin out Chart
R: MaxxPower Unit Wiring Diagrams
• Circuit Diagrams
• Photos with Call Outs
• Parts Information
• Additional Resources
• SRT Information

Basic Troubleshooting
Prior to replacing any components, these basic electrical checks should be performed.
• System will not turn on.
• System starts and cools, but then stops cooling or shuts off.
• Verify proper power and ground is present at the system controller. (Load test the circuits with a headlamp). If the complaint is the system stops cooling,
verify you still have power and ground at 31 and 32 when the issue occurs
• Verify 12 volt input to pin 6 from the Cool Switch
• Verify ground control output from pin 3 to the Compressor Relay and Condenser Fan Relay
If you have ground control from pin 3 to the relays and the system is still not operating properly, the system controller is not at fault. Continue with further
diagnostics.

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• Verify proper voltage at pin 30 of the Compressor Relay. (Load test the circuit with a headlamp).
◦ If you do not have proper voltage at this point, you need to check the truck wiring from the fuses in the battery box to the relay terminal.
• Verify the relay engages and power is present on the output pin 87 to the 60A Maxi Fuse.

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• The 60A fuse feeds power to the compressor controller circuit board
• Check the 4 pin connector between the fuse and the compressor controller circuit board, ensuring the terminals are fully seated and locked.
• Verify proper power and ground at pins C1 and C2 of the compressor controller connector. (Load test the circuits with a headlamp).

• Depending on the type of compressor controller, you will have one of the 2 style connectors on the compressor.
• Check for 6 volts cycling on each of the three wires.

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Component Identification and Location
Navistar main system fuses

Navistar main system fuses in battery box:

• Location: Inside battery

box
• These fuses are identified on the wiring diagram as F6 and F7

A-E: Fuses and Relays:

A: Compressor Fuse 60 Amp (Maxi)
• This fuse provides short circuit protection for the compressor.
• Location: On the control center

B: System Controller Fuse 10 Amp (Mini)
• This fuse provides short circuit protection for the unit controls.
• Location: On the control center

C: Blower Fuse 20 Amp (Mini)
• This fuse provides short circuit protection for the evaporator blower.
• Location: On the control center

D: Condenser Fan Fuse 20 Amp (Mini)
• This fuse provides short circuit protection for the condenser fan.
• Location: On the control center

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E: Relays
• Location: On the control center
• Compressor Relay
•

This relay controls the voltage to the compressor controller.
• (ENGINE OFF MODE)

Condenser Fan Relay
This relay controls the voltage to the condenser fan.
(ENGINE OFF MODE)
Blower Relay
This relay controls the voltage to the evaporator blower.
(ENGINE OFF and ENGINE ON MODE)

F: Switches / Fan and Temperature Control Display
• COOL / No Idle switch:
• Lights up and starts the MaxxPower A/C unit at default settings in the parked mode.

HEAT / No Idle switch:
Lights up and starts the MaxxPower unit and auxiliary coolant heater at default settings in the parked
mode.

LED Display:
Allows for temperature and Blower speed adjustment of the MaxxPower unit when operating in A/C or
heat mode.
• Operates like standard Auxiliary HVAC when the engine is running.
• MaxxPower A/C Unit and Auxiliary Coolant Heater - stop when, engine is started, unit is shut off or
batteries are depleted.

F: Switches / Fan and Temperature Control Display:

G: System Controller:
• This device stores the operating program and controls the MaxxPower unit.
• Location: Under the bunk, next to blend door motor, under the grey 32 pin

connector.

H: Compressor Controller:

G: System Controller:

• This device controls the output voltage to the variable speed compressor.
• Location: On the top / rear area under the plastic access cover.

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I: Linear Power Module (LPM):
• This module controls the amount of voltage delivered to the evaporator blower

creating variable blower speeds.
• Location: On the blower wheel housing.

H: Compressor Controller:
J: Blend Door Actuator:
• This actuator operates the blend door, changing air flow path through the

MaxxPower evaporator coil and heater core.
• Location: Under the bunk, near the blower motor.

K: Inlet Temperature Sensor:
• This sensor monitors the return air temperature in front of the evaporator coil.

I: Linear Power Module:

L: Discharge Temperature Sensor - Freeze Switch:
• This sensor monitors the evaporator outlet temperature as it enters the vehicle duct

system.

J: Blend Door Actuator:
M: Evaporator Blower:
• This blower pulls air through the evaporator coil or heater core and blows

conditioned air into the interior of the sleeper. This blower operates with parked (noidle) and engine driven systems.

N: Condenser Fan:
• This blower draws air from outside the truck, through a section of the louvered door

K-L: Inlet and Discharge Temperature Sensor:

on the passenger side and pushes it through the condenser coil to cool the
refrigerant flowing through the system. The hot air is exhausted out the same louver
panel on the passenger side of the truck.
O:High Pressure Switch:
•

This brazed pressure switch will open and prevent the operation of the compressor
due to high internal pressure. It is NOT serviceable.

M: Evaporator Blower:

P: Compressor

• This unit is part of the hermetically sealed refrigeration system.

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N: Condenser Fan:

Q: Thermal Limit Switch on Compressor:

• This is a normally closed (auto reset) switch to protect the compressor from high
temperature.
R: Evaporator Inlet Filter:

• This filter protects the evaporator coil from dust and debris.
• It should be inspected and serviced periodically during routine maintenance.

O: High Pressure Switch:

P: Compressor:

Q: Thermal Limit Switch on Compressor:

Diagnostics Table
Problem

Possible Cause

Corrective Action / See Appendix

Test with Engine OFF
Unit Will Not Run or Turn
ON

1.
2.
3.
4.
5.
6.
7.
8.
9.

Loose Connection
No power is available at the unit
Blown fuse or fuses
Check Voltage path to controller and
switches
Defective Switch on Control panel
System Controller Defective
Park brake switch defective or wrong
logics
Broken wire or defective wire harness
Check for Fault code

1. Confirm all connections are tight, including ground lugs, and terminals
crimped on wires and battery cables.
2. Check ALL batteries for Voltage. Low voltage disconnect is set to
11.8vdc
3. Check all fuses, F6 and F7 are Navistar main system fuses in the
battery box. See photo above.
4. Check for 12 volts through fuse F6 continuing through System
Controller Fuse to Condenser Fan Relay and Blower Relay Coils, Pin
32 of the System Controller and to the control panel switches as vbat.
See appendix, A, B, and J.
5. Check switch continuity. See appendix B.
6. Test System Controller. See Appendix J.
7. Only relevant if key is in the ACC position. Always perform initial
diagnostics. Eng OFF / Key OFF see appendix J.
8. Inspect wiring harness and all ground wires.
9. View faults on the information display or check communication using
Diamond Logic Builder or Edith

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IK1900198 - MaxxPower No Idle Battery-Powered A/C System Diagnostic Guide.

Unit Runs- But Does Not
Blow Cold Air

1. Airflow blockage
2. Compressor Fuse or Relay
3. Compressor Controller connections /
defective compressor
4. System Controller
5. High pressure switch
6. Evaporator discharge temp sensor /
Freeze switch defective
7. Compressor thermal switch
8. Blend door position
9. Evaporator blower
10. Loss of charge (Refrigerant System not
serviceable)

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1. Clear any blockage from recirculation grill or louvers. Also check
condenser inlet and outlet for restriction (outside truck)
2. Check Compressor Fuse and Compressor Relay. See appendix C, E
and K.
3. Confirm all wire harness plugs are connected. Test Compressor
Controller. See appendix K.
4. Check System Controller and compressor speed signal from system
controller to the compressor controller. See appendix J and K.
5. Check high pressure switch and condenser fan. See appendix D and L.
6. Check sensor. See appendix F.
7. Check normally closed thermal switch. See appendix I.
8. Check Blend door operation. See appendix H.
9. Check Evaporator blower and linear power module (LPM). See
appendix M.
10. If all tests check OK, a loss of refrigerant charge may have occurred.
NOTE: This unit has a dual core evaporator. It uses refrigerant from the
engine driven compressor during engine running mode. If all electrical
components work, including the electric refrigerant compressor and the
unit does not cool, please call Navistar dealer. You can try operating
the unit ENGINE running.

Unit Cycles On and Off

1. Poor electrical connection.
2. Condenser fan inoperative.
3. Air flow blockage causing high pressure
or freeze condition

1. Check all electrical connections.
2. Check condenser fan. See appendix L.
3. Check for restricted airflow outside truck at condenser inlet and outlet