Coolant Low Indicator

A coolant low indicator is standard equipment on all instrument clusters. The coolant low indicator is located near the lower edge of the instrument cluster, to the left of the multi-function indicator display. The coolant low indicator consists of the International Control and Display Symbol icon for "Low Engine Coolant" imprinted within a rectangular cutout in the opaque layer of the instrument cluster overlay. The dark outer layer of the overlay prevents the indicator from being clearly visible when it is not illuminated. A red Light Emitting Diode (LED) behind the cutout in the opaque layer of the overlay causes the icon to appear silhouetted against a red field through the translucent outer layer of the overlay when the indicator is illuminated from behind by the LED, which is soldered onto the instrument cluster electronic circuit board. The coolant low indicator is serviced as a unit with the instrument cluster.

The coolant low indicator gives an indication to the vehicle operator when the engine coolant level is low. This indicator is controlled by a transistor on the instrument cluster circuit board based upon cluster programming and a hard wired input received by the cluster from the engine coolant level switch. The coolant low indicator Light Emitting Diode (LED) is completely controlled by the instrument cluster logic circuit, and that logic will only allow this indicator to operate when the instrument cluster detects that the ignition switch is in the On position. Therefore, the LED will always be off when the ignition switch is in any position except On. The LED only illuminates when it is provided a path to ground by the instrument cluster transistor. The instrument cluster will turn on the coolant low indicator for the following reasons:
- Bulb Test - Each time the ignition switch is turned to the On position the coolant low indicator is illuminated for about two seconds as a bulb test.
- Engine Coolant Level Switch Input - Each time the cluster detects an appropriate input on the low coolant fluid level sense circuit (engine coolant level switch resistance low = engine coolant level low) while the ignition switch is in the On position, the coolant low indicator will be illuminated. The indicator remains illuminated until the low coolant fluid level sense input to the cluster changes (engine coolant level switch resistance high = engine coolant level full), or until the ignition switch is turned to the Off position, whichever occurs first. The engine coolant level switch also features a diagnostic resistor connected in parallel between the switch input and output to provide the cluster with verification that the low coolant fluid level sense circuit is not open or shorted.

The engine coolant level switch integral to the coolant bottle provides a hard wired input to the instrument cluster circuitry through the low coolant fluid level sense circuit. The engine coolant level switch and the low coolant fluid level sense circuit to the instrument cluster can be diagnosed using conventional diagnostic tools and methods. For proper diagnosis of the instrument cluster circuitry that controls the coolant low indicator, a DRBIII(R) scan tool is required. Refer to the appropriate diagnostic information.