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There are four standard Terrain Settings: Highway; Cross Country; Mud, Sand & Snow; and Emergency. Should you require any additional settings such as Kneeling position, to facilitate transport height or wheel loading, please consult factory.

The individual sub-assemblies that provide the above tire pressure settings are described as follows:

SWITCH-PACK CONTROLLER

This Controller is of a digital design and interfaces with two PCB’s, one each located in the switch-pack and the cover of the manifold. The PCB located in the switch-pack drives and controls the input while the PCB in the manifold activates the manifold to start the CTI operation. The results of the automatic operation are displayed on the numeric display. The controller operates on 5 VOLTS after the original 24 VOLTS supply has been reduced and conditioned.

MULTIPLE CHANNEL SYSTEM

The CTI system from CM Automotive is available as a single or a dual channel system. Single channel means that all tires are connected to the same channel. Dual channel systems allow two selected groups of tires, each connected to a dedicated channel. Additional multiple channel systems are not popular and, as a consequence, we do not have these in 3 production. However, up to a four channel configuration can be produced but it is cost effective only on large quantity programs. Please consult the factory.

OVER SPEED CONTROL

For tire safety a speed control is necessary. As the vehicle speed increases over and above the set point for a given tire pressure and for one minute time period, an amber light will start blinking on the controller, indicative of the higher speed. When the one minute time period is exceeded, the CTI system is activated to inflate the tire to the next higher setting and lowering the vehicle speed has no effect. After the tires have been inflated to the next higher setting the vehicle speed can be lowered and the controller reset to deflate the tire to a lower pressure setting.

TIRE PRESSURE MEASUREMENT

The pressure transducer selected for our CTI system is a name brand from Texas Instrument. This company has been resold after relocating. For the last 30 years and under new ownership, we have had the same reliability and performance from the product. The transducer has the measuring range of 150 psi. Software provides tire pressure calculations to include temperature compensation. Such measurement improves the overall accuracy of the adjusted tire pressure.

PRIORITY PRESSURE SWITCH

As the name suggests, the pressure switch provides for the priority of air to be supplied to the brakes. When the CTI system is in full operation and other devices like windshield wipers and brakes are also operating, the heavy consumption of air may lower the air supply pressure. When uninterrupted, the air supply pressure could dip below the minimum operating pressure for the brakes. The priority pressure switch is set to stop CTI operation at 94 psi, maintaining the balance of air pressure in reserve for the vehicle brake operation.

BLACKOUT MODE

The CTI Controller works with two separate electronic circuits; LED’s and power circuit, and both circuits can be switched off independently. Therefore, the LED lighting can be turned off while the power circuit continues to operate the CTI system. For a hardware connection, the CTI controller provides a single wire that the customer can integrate in to a vehicle blackout mode switch to turn off the LED lamps of the CTI system.

LOW AIR INTERRUPT

As noted in the description of the priority pressure switch above, during the decreasing pressure mode the pressure switch trips out at 94 psi. This is also known as the “low air interrupt” that also shuts off the CTI system. As the compressor runs, the air supply pressure continues to build up. When the pressure reaches 115 psi, the pressure switch closes and reactivates the CTI system. The tire pressure will start building up from where it left off when the low air interrupt occurred.

Such interruptions can be a consequence of a low output air compressor. On a 6×6 vehicle I have noticed 8 interruptions from emergency to highway increasing the inflation time to 40 minutes. The compressor size was 10 cubic feet per minute against the recommended size of 15 cubic feet per minute. An adjustment of the inflation valve orifice to lower flow allowed no interruption and lowered the inflation time to 20 minutes. Please call the factory for help should you find yourself in the above situation.

AUTO TIRE PRESSURE RECHECK & ADJUST

The CTI controller provides a periodic check of the tire pressure. An adjustable timer on board is available from 30 minutes to 60 minutes to activate the CTI cycle. Upon recheck, all tires are opened to the manifold so the transducer can measure the tire pressure. If the measurement falls within the tolerance of the last adjusted tire pressure, the system shuts off. If not, the tire pressure is adjusted to the last tire pressure setting, the CTI system shuts off and the timer resets.

NUMERIC DISPLAY

The switch-pack controller houses a digital display that provides CTI operational information to the driver. During the tire pressure adjustment process the actual tire pressure is displayed in two digits, increasing for inflation or decreasing for deflation along with the location of tires; front or rear. The second line also displays the title of the process like,Tire pressure adjustment.