Small Test Light Will Not Find Some Shortto Grounds

All the ground paths in this circuit will cause the light to be bright with or without the short-to-ground present. A larger load such as a headlight requires more current flow will work better.

H POWER SOURCE (Current Flow Chart)

Page Nos. of Related Systems

Code or \ Location \

Page Nos. of Related Systems

Code or \ Location \

CB or Fuse

223 228 228 199 228 234 234 234

Al A2 A3 A7 A10

15A ' 15A ' , 20A 7.5A 7.5A 15A J5Aj JOA JOA J5A ' 30A ' 40 A "










15A ~15A


228 228 234

A18 A21 B1 B2 B3

228 234

116 228 150 62 234 156

B4 B5 B6 B9 CI

Some technicians use a short finder or circuit breaker in place of the fuse. A short finder kit consists of a circuit breaker and a low-quality inductive type ammeter or compass. While the circuit breaker "pulses" the circuit OFF and ON, you follow the wiring with the inductive ammeter. When you reach the location of the short-to-ground, the ammeter will no longer show any current flow in the wire.

The success rate using a short finder is mixed. Isolating and following a circuit's wiring behind the instrument panel, or through harnesses which have additional wires that have normal current flow through them can be difficult. Keep in mind that depending on the gauge of wire and the type of insulation (vinyl or PVC), a circuit breaker (even a short finder) will allow momentary "bursts" of current flow that may exceed the capacity of wiring, possibly causing heat damage to the insulation or wire, and could also damage adjacent wires in the harness.

The Bottom Line The best tool to use for a finding a short-to-ground is a sealed beam headlight or a load which uses a few amps. A test light, short finder or circuit breaker can be used, but precautions must be taken to prevent damaging the harness, or mis-diagnosing the problem.

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    What is a 1985 Celica defog CB?
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