IDLER & BEARING AS 3989341 - Caterpillar

Illustration 1. 6V4190 Auto Programmer Group.Used with the programmer group, the multitach has the ability of two tachometers. The auto programmer lets you use the magnetic and photohead inputs to make rapid comparisons of two speeds. A light push of the finger can let you make speed comparisons of a number of engine set-ups, like the measurement of fan speed against engine speed - almost immediately.
...It's easily adaptable to different applications.
Specifically, two pulses per revolution (P/REV) numbers, one for magnetic and one for photo operation, can be permanently stored in the programmer's memory. Since access to the programmer's controls is fast - they are on the outside of the case - P/REV numbers can be changed easily for different applications.
The 6V4190 Auto Programmer Group is easily installed on all 6V2100 Multitachs in replacement of the original rear cover. A 6V4865 Auto Programmer Connector is necessary for installation of the auto programmer. See Illustration 2. Make an inspection of your multitach to see if it has the 6V4865 Auto Programmer Connector. It is necessary to remove the rear cover of the multitach to make this inspection.
Illustration 2. 6V4865 Auto Programmer Connector.Remove six screws and separate the rear cover from the front cover. Illustration 3 shows the location of the six screws. If your multitach already has a 6V4865 Auto Programmer Connector it will be above the blue connector. Illustration 4 shows the location of the 6V4865 Auto Programmer Connector. All 6V2100 Multitachs assembled after April, 1981 have this connector installed. If your multitach does not have this connector, one must be ordered and installed before the auto programmer installation can be made.
Illustration 3. Location of screws to be removed.
Illustration 4. Location of 6V4865 Auto Programmer Connector.Special Instruction "Installation And Use Of 6V4190 Auto Programmer", Form SEHS7930 gives the necessary information for installation and use of the 6V4190 Auto Programmer and the 6V4865 Auto Programmer Connector.
Be sure to read thoroughly and understand Special Instruction "Using The 6V2100 Multitach and 6V3121 Multitach Group", Form SEHS7807, before the 6V2100 Multitach with the 6V4190 Auto Programmer Group installed is to be used.