Why generators show "low coolant level": 10 documented causes and brand-specific fixes, compiled across 7 manufacturers.
Low coolant level; bad low coolant level sensor; bad wires 573 & 573A; bad controller
2 brands- Generac: Test 80 – Check Coolant Level; Test 77 – Test Low Coolant Level Sensor; Test 78 – Check Wires 573 & 573A; Add coolant and check for leaks; Replace low coolant level sensor; Repair or replace wires as necessary; Replace controller
- Nexus: Test 80 – Check Coolant Level; Test 77 – Test Low Coolant Level Sensor; Test 78 – Check Wires 573 & 573A; Add coolant and check for leaks; Replace low coolant level sensor; Repair or replace wires as necessary; Replace controller
Engine coolant level has fallen below the warning trip point
1 brand- Cummins/Onan: If generator is powering critical loads and cannot be shut down, wait until next shutdown period, then follow code 235 procedure; if engine can be stopped, follow code 235 procedure; If generator is powering critical loads and cannot be shut down, wait until next shutdown period, then follow code 235 procedure; if engine can be stopped, follow code 235 procedure.
Engine coolant level has fallen below the shutdown trip point
1 brand- Cummins/Onan: Allow engine to cool down completely before proceeding: check coolant level and replenish if low, look for possible coolant leakage points and repair if necessary; reset control and restart after locating and correcting problem; Allow engine to cool down completely before proceeding; check coolant level and replenish if low; look for possible coolant leakage points and repair if necessary; reset control and restart after locating and correcting problem.
Engine coolant level has fallen below the warning trip point.
1 brand- Cummins/Onan: If generator is powering critical loads and cannot be shut down, wait until next shutdown period, then follow code 235 procedure. If engine can be stopped, follow code 235 procedure.
Engine coolant level has fallen below the shutdown trip point.
1 brand- Cummins/Onan: Allow engine to cool down completely before proceeding. a. Check coolant level and replenish if low. Look for possible coolant leakage points and repair if necessary. b. Reset control and restart after locating and correcting problem.
The engine coolant level fell below the optional coolant level sensor
1 brand- Cummins/Onan: Add coolant as necessary and repair leaks
Insufficient liner standout; Excessive liner standout differential between cylinders; Low head bolt clamping loads; Rough/damaged liner flange surface; Cracked/deformed gasket combustion flange; Out-of-flat/damaged/rough cylinder head surface; Missing/mislocated gasket fire ring; Block cracked in liner support area; Gasket section dislodged, missing (blown); Excessive fuel delivery; Advanced injection pump timing; Hydraulic or mechanical disturbance of combustion seal
1 brand- PowerTech: See HEAD GASKET INSPECTION AND REPAIR SEQUENCE in Section 02, Group 020 of this manual
Excessive liner standout; Excessive liner standout differential between cylinders; Low head bolt clamping loads; Out-of-flat/damaged/rough block surface; Out-of-flat/damaged/rough cylinder head surface; Cracks/creases in gasket body surfaces; Damage/voids in elastomer beading of gasket
1 brand- PowerTech: See HEAD GASKET INSPECTION AND REPAIR SEQUENCE in Section 02, Group 020 of this manual
Coolant level is low and needs to be replenished; The sensor or harness is defective
1 brand- Cummins/Onan: Check the level of coolant in the radiator; Add coolant to the radiator if necessary; If the coolant level is normal, isolate the source of the low coolant signal (GND signal); Disconnect the signal lead at the sender and reset the control; If the 197/235 message drops out and does not reappear, replace the sender; If the 197/235 message reappears and remains after the control is reset, remove connector P7 from the base board and check for continuity from P7-32 to the ground; If there is continuity, replace the harness.
Engine coolant level has dropped below the shutdown threshold for low coolant level
1 brand- Cummins/Onan: Refer to fault code 197