Six-step diagnostic procedure

Apply six-step diagnosis to a real problem

Step 1 Confirm the symptom	Asked the customer to point out the light which is not working Confirm that it is the left front parking lamp, and only the left front, which is not working The symptom is real - move on to Step 2.
Step 2 Gather information	a. Question the car’s owner about the park light’s use and behaviour up to the time of noticing the fault. Some sample questions and answers are in the table below this one. b. Do the “look and feel” test. You find: The park light is mounted firmly in the plastic front bumper. The panel fit is good. The bumper is not loose. Looking behind the lamp, we can see that the wiring loom is intact and securely clipped to the bumper. We remove the globe and inspect it - sure enough, it’s blown! But what causes globes to blow?
Step 2 Gather information – cont.	c. Use other information sources: Even though we reckon we know this stuff, let’s check the workshop manual for any further information. The manual provides this chart: Symptom Cause Globe blown Old age - very high number of on-off cycles Vibration – loose lamp holder, loose panel mounting very rough roads Loose electrical connections – number of rapid on-off cycles High circuit voltage – over stressed filament Manufacturing defect Now that we have some reliable information, we can move on to Step 3.
Step 3 Consider the information and evidence gathered	What have we learned from our investigation so far? Have we got enough information and evidence? Can we confidently say what caused the globe to blow? Or can we at least narrow down the possibilities? Let’s compare each of the possible causes from the workshop manual with the evidence and judge how likely each possible fault is.
Feedback loop	Test 1 - We need more information. Time to get the multimeter out! Starting the engine and turning on the park light, we back-probe the wiring connector at the faulty lamp with our multimeter set on the 20 volt range. The result: 15.1 volts supplied to the light. Is this the right voltage? Only one way to tell - look it up in the workshop manual! The lighting circuit is part of the electrical circuit. The electrical circuit is supplied by the alternator. According to the workshop manual - Alternator regulated output voltage = 14.0 – 14.2 volts Compare the measured circuit voltage with the manufacturer’s specifications - it’s nearly a volt too high! We can now say that the most likely cause of the blown globe is high circuit voltage, which over-stressed the globe’s filament, causing early failure. Test 2 - We need to test the battery to make sure it hasn’t been damaged by over charging. Luckily it’s OK.
Step 4 Locate the fault and its cause	We now know the fault is a blown globe, and its cause is high circuit voltage which over-stressed the globe’s filament.
Step 5 Repair the fault and its cause	The blown globe must be replaced with a new one. The circuit voltage must be reduced to manufacturer’s specifications. Alternator output voltage on this car is set by the voltage regulator inside the alternator. The regulator needs to be replaced, but experience tells us that the alternator brushes will have suffered some natural wear as well. We could: overhaul the alternator in our workshop fit a change-over reconditioned unit supplied by the local auto electrician fit a brand new unit supplied by the dealership. Our recommended repair is to fit the reconditioned unit, which has been bench-tested and is guaranteed. It is equivalent to the new unit, but is much cheaper. We won’t do the overhaul ourselves because our workshop is fully booked, and in any case we can’t do the job any cheaper than the reconditioned unit. We should also advise the customer that all of the vehicle’s light globes have been stressed by excessive circuit voltage. In the interests of customer satisfaction, it would be wise to replace all of the safety-related globes to avoid any subsequent “old-age/ stress related” failures in the near future.
Step 6. Check all systems and confirm fault is fixed.	We test all functions of the lighting system for correct operation, switching, illumination etc. Re-check alternator regulated voltage, following manufacturer’s procedures. The job is complete, apart from the paperwork.

Step 2 a. Gather information -Question the car’s owner

What questions could we ask this customer?

Questions	What information do we want?	Answer
How often do you use the park lights?	We want to judge how much service the light has given prior to failure	About 2 hours each week
What sort of driving do you do?	We want to know if the car travels on rough roads a lot	Mostly city driving-sealed roads
Has it ever stopped working before?	To see if we’re chasing a recurring fault	No
Have any other lights stopped working in the past?	To get a history of the car’s lighting problems	Yes, a tail light and one headlight, at different times
What did you do about those failures?	We want to know about any work done on the lighting system prior to this	A friend put new globes in- he said they were blown
Have you noticed anything else unusual about the operation of your car’s lights recently?	We want to know if there have been any other symptoms such as flickering, changes in brightness etc	No
Has any other work been done on the front end of the car recently?	This could point to problems created during an unrelated repair, such as panel damage	No

Activity 4

Question 1

A customer complains that his car’s engine “misses under load”.

What could you do to confirm that this symptom exists?


Question 2

You need to get more information about the fault. Write down four useful diagnostic questions you could ask the owner.

1.

2.

3.

4.

Question 3

Choose a workshop manual and look up the manufacturer’s trouble shooting information for the symptom of “engine missing under load”.

OR choose a different symptom you would like to investigate.

Complete the table below by filling in the possible causes of this problem.

Symptom	Possible causes

Question 4

The steps of a typical diagnostic procedure are set out below in boxes.

Explain the purpose and importance of each step.

1. Confirm the symptom		Purpose
2. Gather information		Purpose
3. Consider the information and evidence gathered		Purpose
4. Locate the fault and its cause		Purpose
5. Repair the fault and its cause		Purpose
6. Check all systems and confirm fault is fixed.		Purpose

Question 5

Here are some questions you might ask a client to collect information about a vehicle problem.

Why would you ask each question? How could the customer’s answers help you to diagnose the problem?

1. 
   “How often does the problem happen?”
   

2. 
   “How old is the vehicle?”
   

3. 
   “When does the problem occur?”
   

4. 
   “Have you had any work done on the vehicle recently?”
   

5. 
   “Do many different people drive the vehicle?”
   

Ask your trainer to check your results before proceeding.

Trainer Signature: .............................................................. Date: .....................

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Activity 5

Question 1

Create a diagnostic procedure for yourself in the space provided.

Include the six steps you have learned about.
Include all safety precautions necessary for safe work practices in your workplace.

You can design your procedure as a flow chart, or using dot-points, as long as another person could easily follow your reasoning.

Remember to:

• 
  Ask questions and collect information
  
• 
  Think about all possible faults
  
• 
  Describe any tests you make
  
• 
  Recommend an appropriate repair.
  

The problem:
I’ve got a flat tyre!

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Reporting and documenting diagnosis and repairs

Often in an automotive workshop you will need to write things down, record them, and pass them on to other people.

This section deals with the documentation and reporting that may be required by diagnosis tasks.

Why do we need to document the diagnostic process?

Recording information about a diagnostic procedure is important so that:

• 
  The technician can keep track of the process eg tests done and their results
  
• 
  The technician can see the build-up of information which will help them eventually recognise the fault
  
• 
  The business can communicate accurately with the customer from the start of the diagnostic procedure until the repair is completed and paid for
  
• 
  The business can obtain authority to repair at the appropriate stages as the procedure is worked through
  
• 
  There is an accurate record if there is any dispute over the work done
  
• 
  There is a service record can be a helpful reference for future jobs.
  
  

The information should always be written down in an organised way so that anyone who looks at it can understand it. It is risky and bad practice to rely on your memory – the information needs to be written down, and not on a scrap of paper that can easily be lost or misplaced!

When a customer approaches a business for a fault to be diagnosed, most businesses set up a job card for the particular job. The job card becomes part of the vehicle’s service record, which is a file of information maintained by the workshop over time.

Set up a Job Card

When a numbered Job Card or Repair Order is set up, you should record the following information:

• 
  Owner’s details
  
• 
  Car’s details
  
• 
  Customer’s concerns about the vehicle
  
• 
  Customer’s signature in the‘Authority to Repair’ space on the card.
  
  

The Authority to Repair is signed on the understanding that the customer will be consulted if the repair is going to be bigger or more expensive than first thought.
Example:

Directory: auto
auto -> Unit: Automotive and Auto Body
auto -> Word Wall Chants Use these as fun ways to practice word wall words at home!
auto -> A message from Mr. Dryden
auto -> Major works data sheet
auto -> U. S. Steel Corporation, Elbert H. Gary Gary was corporate lawyer who became the U. S. Steel Corporation president in 1898. U. S. Steel was the leading steel producer at the time
auto -> Identify the choice that best completes the statement or answers the question
auto -> Historical periods to memorize
auto -> Geography handbook
auto -> It rose out of the tropical Pacific in late 1997, bearing more energy than a million Hiroshima bombs

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