RELAY 2852068 - Caterpillar

All 24 Volt Electric Starting SystemsReference: Service Magazine; December 10, 1984; Page 4; "Starters That Remain Engaged After Engine Is Running". Starters sometimes remain engaged after the engine starts due to a faulty start switch, or faulty relay, or accidental actuation of the start switch by the operator after the engine is running. This can damage the: ... Pinion drive.... Ring gear.... Starter.... Batteries.
All cranking circuits are similar to that shown in either Illustration 1 or 2. Either circuit can be modified so when the engine starts the starter can not be engaged.
Illustration 1. Typical 24V starting circuit without a start relay.
Illustration 2. Typical 24V starting circuit with a start relay.For Illustration 1 circuit, add a 3T2171 Relay Assembly and a 9F3099 Switch (Start Relay). See Illustration 3.
Illustration 3. Typical 24V starting circuit with both the relay assembly and switch (start relay) added.For Illustration 2 circuit that already contains the 9F3099 Switch or equivalent, add only a 3T2171 Relay Assembly. See Illustration 3.
With the correct modification, when the engine starts, the alternator (R) terminal causes the 3T2171 Relay Assembly to pull in and inhibit the 9F3099 Switch. This prevents actuation of the starter.