Page
22 of 39
Number
SM001-300
HVAC: Idle Management System
If the separator switch tests okay, reconnect the separa-
tor wires, unplug the BMS for at least 15 seconds, recon-
nect BMS and repeat BMS test. If the BMS will not
operate the separator, replace the BMS.
M. Can Bus
NOTE
Before checking Can Bus, if control lights for a few sec-
onds and goes out, disconnect the controller harness
at the controller unit. Reconnect to reset. If unit does
not run, continue with Can Bus tests.
Also, before checking can bus, disconnect BMS and
retry system for operation.
POWER TO BOTH DEVICES (EHVAC AND BATTERY
MANAGEMENT SYSTEM) MUST BE DISCONNECTED
TO PERFORM THESE TESTS.
The communication from the BMS to the EHVAC unit
travels through the controller harness and the BMS har-
ness. These harnesses have a twisted pair of wires, yel-
low (Can H) and green (Can L). These harnesses should
be loomed and routed away from any components in the
truck that could cause interference, such as florescent
lights, etc.
First, determine what part of the can is affected. If you
lose the Can Bus to the BMS, the EHVAC unit will oper-
ate normally. You will not see volts and amps displayed
on the service screens and the battery symbol will indi-
cate full as a default.
If the digital controller does not communicate to the
EHVAC unit, the unit will not operate. If the unit is operat-
ing and loses communication for more than 5 seconds it
will shut down.
The Idle Management System has the CAN BUS 120
ohm resistors built internally in the digital control panel
and Battery Management System (BMS). To test the
CAN BUS, remove digital control and disconnect the har-
ness. Check across pins 3 and 4 on the control. You
should measure 120 ohms. Back probe the harness. You
should again measure 120 ohms with harness connected
to the unit and BMS.
If not, check at BMS. Disconnect harness at BMS.
Check pins 6 and 7 on the BMS. You should measure
120 ohms. Reconnect the harness to the digital control.
With harness still connected to control and unit, back
probe harness. You should measure 120 ohms.
Reconnect the harness to the BMS. With all harnesses
connected you should measure 60 ohms.
N. Testing the Espar Heater Connected to
the EHVAC Digital Controller
The Espar heater control harness connects to the
EHVAC unit using a 6 pin connector. Pin 1 is heater
option. This is a 12 volt input from the Espar heater to the
main controller pin C3, signaling that the Espar heater is
connected to the system. Pin 2 is heater enable. This 12
volt output from the unit to the Espar heater enables the
heater to turn on. Pin 3 is ground. Pin 4 is heat level. This
wire transmits the temperature signal from the EHVAC
temperature sensor to the heater ECM. The Espar heater
will regulate heat according to this temperature and the
set point of the control. When checking resistance on the
temperature circuit, always use the brown/white for refer-
ence.
Selecting HEAT mode will turn the ENABLE signal on.
The heat level will be controlled through the EHVAC
(gray/red) wire coming from the unit on pin 4. This is a
variable resistance signal from the EHVAC digital control-
ler. Resistance ranges from approx. 1.8k ohms for low
heat and 2.2k ohms for high heat.
First, set the EHVAC digital controller to HEAT mode, set
the temperature to full heat 85 degrees. When testing the
heater, the ambient temperature in the sleeper must be
below 85 degrees.
Check for the heat enable signal between the yellow
(positive) and brown/white (negative) wires. You should
have 12 volts. If the digital controller shows the tempera-
ture set point and heat mode and you do not have 12
volts, check the EHVAC internal system controller output
from pin C15. If you have 12 volts on pin C15 but not out-
side the unit, you have a bad connection or the harness
is defective. If you do not have 12 volts on pin C15, you
have a defective system controller.
With 12 volts on the heat enable, check the heat level
signal on the EHVAC (gray/red) wire using the
brown/white as ground. This variable resistance signal
will range from approx. 1.8k ohms to 2.2k ohms. If this
resistance is within range, the heater should operate. If it
