Section 13-09C: Gauges, Warning Devices, Low Coolant Level Indication System
1994 Mustang Workshop Manual
DIAGNOSIS AND TESTING

Pinpoint Tests

  

PINPOINT TEST A: LOW COOLANT LEVEL INDICATION NOT OPERATING PROPERLY

 

A1 CHECK FOR VOLTAGE AT FUSE 15 (10A)

Yes
GO to A3.

No
GO to A2.

 

A2 CHECK VOLTAGE SUPPLY TO SWITCH

Yes
SERVICE Circuit 640 (R/Y) for short to ground. RESTORE vehicle. RETEST system.

No
REPLACE fuse 15 (10A). RESTORE vehicle. RETEST system.

 

A3 CHECK CIRCUIT 640 (R/Y) FOR OPEN

  • Disconnect low coolant level sensor.
  • Using an ohmmeter connect one lead to output side of fuse 15 (10A), connect second lead to Circuit 640 (R/Y) at low coolant sensor connector.
  • Measure resistance.
  • Is resistance 5 ohms or less?
Yes
GO to A4.

No
SERVICE Circuit 640 (R/Y) for open circuit. RESTORE vehicle. RETEST system.

 

A4 CHECK LOW COOLANT SENSOR GROUND

  • Using an ohmmeter connected to a known good ground, connect second lead to Circuit 57 (BK) at coolant sensor connector.
  • Measure resistance.
  • Is resistance 5 ohms or less?
Yes
GO to A5.

No
SERVICE Circuit 57 (BK) for open circuit. RESTORE vehicle. RETEST system.

 

A5 CHECK LOW COOLANT SENSOR

  • Using a jumper wire, connect one end to Circuit 57 (BK), connect other end to Circuit 794 (LB) at coolant sensor connector.
  • Did low coolant lamp illuminate?
Yes
REPLACE low coolant level sensor. RESTORE vehicle. RETEST system.

No
GO to A6.

 

A6 CHECK CIRCUIT 794 (LB) FOR OPEN

  • Using an ohmmeter connect one lead to Circuit 794 (LB) at low coolant sensor connector, connect second lead to Pin 2, Circuit 794 (LB) at instrument cluster connector.
  • Measure resistance.
  • Is resistance 5 ohms or less?
Yes
GO to A7.

No
SERVICE Circuit 794 (LB) for open circuit. RESTORE vehicle. RETEST system.

 

A7 CHECK LOW COOLANT INDICATOR LAMP

  • Remove indicator lamp, inspect bulb for being burned or damaged.
  • Is bulb OK?
Yes
REPLACE instrument cluster. RESTORE vehicle. RETEST system.

No
REPLACE bulb. RESTORE vehicle. RETEST system.