Intermittent Fault

Intermittent errors can be a challenge to diagnose. Failing to recreate the fault can lead to incorrect diagnosis, lengthy troubleshooting, or unnecessary parts swapping.

Intermittent electrical faults occurs when the parameters create an environment which introduces the error. Paying attention to what the parameters are, that is, under what conditions the fault occur, is important to the diagnosis process.

Relevant questions to ask:

  • What is the frequency in which the fault reoccurs?
  • What is the driver doing when the fault occurs?
  • What is the car doing when the fault occurs?
  • What are the environmental conditions? Cold, hot, windy?

The main parameters are typically put into 3 categories:

  1. Temperature
  2. Vibration
  3. Moisture

Temperature changes, both heat and cold condition can affect electrical components and their ability to operate. Heat can make motors, solenoids, pumps, relays, ignition coils, etc. fail. Errors that occur after a period of “warm-up” time are suspect to temperature related errors. Once you have a direction of which component may be failing, it can be tested using a heat gun to apply heat to the component and its surrounding while testing it for its functionality. If the components fail or struggles to operate as it heats up, the suspicion can be confirmed.

Vibration can trigger loose electrical connections. This will trigger the fault during gear changes, bumpy roads, startup or in some cases – at specific engine revolutions. Troubleshooting this is done via the wiggle test. Components suspected are inspected visually first, and they put to a wiggle test, both on wiring and connections to see if the fault reoccurs. Once the fault can be recreated with the wiggle, the root cause must be identified. This can be a poorly fitting connection, internally broken wire, or corroded contact surface.

Corrosion in connector
Corrosion in connector

For a poorly fitting connection, check the pins to connect firmly with the mating surface. Perform a drag test ensuring the connection between the pin and hole is not too loose. Broken wires will identify them selves as not being connected when bent on certain angles. Electrical corrosion can be detected by its white and green crusty appearance on the electrical connection surface.

Moisture affects electrical component and connections, resulting in short circuit, failing components and accelerated corrosion. If the error occurs under wet conditions, the environment can be recreated with a water spray bottle set on spray/mist or a water hose, depending on the location of the suspected component. Components fitted under the car will usually be protected by separate weather shielding. Components fitted inside the engine bay will usually have limited shielding due to its already protected location.

Tools used for monitoring, while trying to recreate the fault via temperature, vibration or moisture, are bi-directional test equipment, oscilloscope, or a multi-meter with graphing capability. Regardless of tool used, it is important that the monitoring can be displayed over a timeline, so a good result can be differentiated by a bad result.