1994/08/29 Caterpillar

Improved Automatic Retarder Control (ARC) {3121}

Usage:

768C (02X),
772B (64W),
776B (6JC),
776C (2TK) Tractors;
769C (01X),
773B (63W),
777B (4YC, 3NF),
777C (4XJ, 8JL),
784B (5RK),
785 (8GB),
785B (6HK),
789 (9ZC),
789B (7EK),
793 (3SJ),
793B (1HL) Trucks;
771C (3BJ),
775B (7XJ),
Quarry Trucks

Description of Change: A new automatic retarder control (ARC) group replaces the former control group. The significant changes are:

* The engine overspeed protection feature has been added. The feature will function even if the accelerator is depressed and/or ARC is turned off. ARC will activate when engine speed reaches 2100 rpm (2475 rpm for 3400 engines). ARC applies the brakes to prevent engine speed from exceeding 2180 rpm (2560 rpm for 3400 engines). ARC will de-activate when engine speed decreases to 2075 rpm (2450 rpm for 3400 engines).

* ARC is improved to eliminate a problem. With the former ARC control group, retarding would not occur when the position of the shift cane was higher than the top gear limit programmed into the EPTC II control. The internal software of the new ARC has been changed to eliminate this problem.

* ARC will now work with the 768C,769C, 771C, 772B, 773B, 775B, 776C, and 777C. The entire ARC system must be installed (control group, valves and wiring).

* The factory default setting for the control speed is changed. The control speed is the engine speed that ARC maintains during automatic retarding. The factory default setting is now 1900 rpm (2230 rpm for 3400 engines). The setting of the control speed is programmable by the user. The range of settings is from 1850 to 1950 rpm (from 2160 to 2300 rpm for 3400 engines). The retarder lamp on the dash will light at 100 rpm less than the control speed setting, but never less than 1800 rpm (2125 rpm for 3400 engines).

* The ECAP service tool can now be used with ARC. The functions available with ECAP are:

Reading logged diagnostic information.

Setting the control speed.

Viewing the real time status of all inputs.

Reading the number of cycles on the ARC valves.

Using the ECAP on ARC requires:

Service Program Module NEXG4521 V1.2

7X-1700 Communications Adapter Kit

NEXG4523 Communications Adapter

7X-1570 Cable (Cat Data Link to Communications Adapter)

Either 7X-1420 Cable (for the old ECAP) or 7X-1851 Cable (for the new ECAP).

* The ARC control now has 12 status indicators within the display area. The former ARC control has 8 status indicators. A new "MODE" indicator is ON whenever the display mode is not mode "-0-". The other three new indicators are unused at this time.

Adaptable To: The new 113-2643 Control Group (ARC) is directly interchangeable with the former 105-1888 Control Group. See Chart A for the effective PIN of the new 113-2643 Control Group.