SERVICE MANUAL
TIREBOSS
TM
Tire Pressure Control
3-6
f:tec\manuals\Service\SERVICEv5.indd - V6-0615
“HEATER CURRENT ERROR” ALERT
Valve Circuit Board 1393-02
(Note: Valve board 1393-02 accommodates both 12V and 24V systems)
This alert appears on the cab controller display to indicate a problem related to the system valve heater circuit
operation.
There are two different conditions that will cause the Heater Current Error Alert to appear. The fi rst, and least
common, is a condition where the heaters are on, and based on the ambient temperature, should not be on; the
second, and most common, is the condition where the heaters are not on, and based on the ambient temperature,
they should be on.
The fi rst problem, where heaters are on and should not be, is pretty easy to diagnose and is typically caused by a
defective or failed relay (relay failed in an on-state, as if energized).
The second problem, where heaters should be on but are not, could be any one or a combination of the following:
Blown heater circuit fuse
Failed heater circuit control relay (relay is off and will not energize)
Broken heater wire(s) or loose heater wire connections
Failed heater element(s)
Incorrect heater(s) installed
Cab controller is not set up properly for the number of installed heaters
Cab controller is not set up properly for the wattage rating of installed heaters
Short description of the valve heater circuit operation:
Valve heater(s) are installed on vehicles used in locations where, at times, the ambient temperatures may be be-
low freezing. Freezing temperatures can prevent proper operation of the system control valve(s) due to moisture,
contained in the air supply, freezing inside the valve(s).
The system valve(s) are located inside of the valve box which is typically mounted on the truck frame behind the
cab. There is a heater element attached to the bottom side of each valve. The heaters are resistive elements
contained in a fl at pad with two wires exiting the pad for electrical connection to the circuit. Also, inside the valve
box is the valve controller circuit board, mounted inside its own enclosure. The circuit which controls turning the
heaters on and off is located on the valve controller circuit board.
Refer to drawing on page 1-8 for location of the following components on valve circuit board:
Heater power positive (+12V/+24V) is supplied through fuse F2 (10 Amp Mini-ATO) and control relay 3CR, located
on the valve controller circuit board. The +12V/+24V connection for the heater(s) is then supplied on Terminal Strip
J2 at terminal 15, marked HT-COM. The ground side connection for the heater(s) is different based on the system
voltage. For 24V systems, heater ground is at terminal 16, marked HT-28V. For 12V systems, heater ground is
at terminal 17, marked HT-14V. Power is only available at HT-COM with the 10 amp fuse in place and the Relay
3CR energized. This relay is activated by the operator controller after receiving a low temperature message from
a temperature sensing element. Each system has one TEMP SENSOR regardless of the number of valves heat-
ers used in the system. The TEMP SENSOR looks like an electrical ring terminal with two wires coming out of it
and is mounted to the side of one of the valves. The TEMP SENSOR wires are connected at Terminal Strip J2 at
terminal 7, marked TH1 and terminal 8 marked TH2. Note that connection of the HEATER
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