In this video I will show you the tests you need to perform on a car with a dead battery. The three main things we must determine:

  1. Does the battery need to be replaced?
  2. Is the alternator charging correctly?
  3. Is there a parasitic drain on the system with the ignition off?

When you have a car that is only driven once a month combined with a cold climate, special attention must be made to the battery drain test. (parasitic drain).

symptoms

  • battery keeps going dead (1 year old battery)

fix 50

  • replace battery

test shown

  • how to test a charging system
  • how to be sure the alternator diodes are okay
  • how to test a battery
  • how to test for a parasitic drain (battery drain)
  • what is the acceptable current flow from a battery with the ignition off

Tools used

  • graphing multimeter (digital multimeter may be used)
  • jump pack (battery jump starter)

end faq

Playlist

Starting, Charging and Battery system problems

Related videos:

How to locate a battery drain (parasitic drain test) Part 1:

How to locate a battery drain (parasitic drain test) Part 2:

Bad Alternator Diode causing transmission/speedometer problems:

end faq

Parasitic Drain Tests (SD Premium videos):

How to test for a battery drain problem (parasitic drain test) - Lexus GS 300:

Alternator parasitic drain classroom review (Lexus GS 300 Case Study):

2011 Caravan Intermittent No Crank, No Start, Dead Battery (TIPM Problems):

end faq


For more information on this topic, I have written a “field manual” called Engine Performance Diagnostics which is available as an eBook or paper book.

Want even more diagnostic training? Whether you are a DIY trying to fix your own car, someone looking to become an auto technician, or a current auto technician that wants to get more into diagnostics, subscribe to ScannerDanner Premium. There is a 14 day free trial.

On ScannerDanner Premium I will bring you right into my classroom at Rosedale Technical College. You will find page for page lectures taken right from my book as well as exclusive classroom type case studies. What is so special about these classroom case studies? I pull live problem vehicles directly into my classroom and we troubleshoot them in real time, using and applying the theory and testing procedures we learn during the classroom lectures. There is no better on-line training of how to troubleshoot automotive electrical and electronics systems anywhere!

 

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0 #2 ScannerDanner 2018-05-04 08:34
Quoting patrickw:
Dear Paul,
I enjoy your videos, you are a great teacher and I have learned so much. I was recently working on a car using my snap on low amp clamp on a mt2400 and I could not get my amp clamp to stay at zero. It would keep going up on the meter with out the clamp being around the cable. I ended up doing the draw test with my amp meter in series. What would cause the mv to go up on its own like that. Thanks

Because the inductive low amp probes are not good at measuring these very small milliamp conditions. I almost never use it for this test because of the exact thing you are describing
0 #1 patrickw 2018-05-03 10:49
Dear Paul,
I enjoy your videos, you are a great teacher and I have learned so much. I was recently working on a car using my snap on low amp clamp on a mt2400 and I could not get my amp clamp to stay at zero. It would keep going up on the meter with out the clamp being around the cable. I ended up doing the draw test with my amp meter in series. What would cause the mv to go up on its own like that. Thanks