How to Use a Parasitic Draw Test Switch & Cable

[mrrsm]

How to Use a Parasitic Draw Test Switch & Cable



PRECAUTIONS:
ALWAYS WEAR EYE PROTECTION
REMOVE ALL RINGS, WATCHES AND JEWELRY
DO NOT CONNECT THE TEST SWITCH TO THE POSITIVE (+) BATTERY TERMINAL
DO NOT OPEN THE TEST SWITCH WITH THE ENGINE RUNNING… ELECTRICAL SYSTEM DAMAGE MAY OCCUR
CHECK THAT ALL CONNECTIONS ARE CLEAN AND TIGHT

BATTERY CONNECTIONS:

(1) Turn the Ignition OFF.
(2) Disable the Under Hood Light.
(3) Remove the (-) Negative Battery Cable.
(4) Install the Test Switch Side Mount Cable Bolt to the (-) Battery Terminal.
(5) Alternatively, Attach the Top Mount Cable Connector to the (-) Battery Post.
(6) Install the OEM (-) Negative Battery Cable to the Test Switch.
(7) Turn the Green Test Switch Knob to the “ON” Position.
(8) Start the Vehicle and Take a Short Test Drive to Test All Normal Systems.
(9) Turn the Ignition Key to the “OFF” Position.
(10) Wait 20 Minutes.
(11) Set the Ammeter to the 10 Amp Scale and Connect the Leads to the Test Switch Terminals.
(12) Turn the Green Test Switch Knob to the “OFF” Position.
(13) Measure the Amperage.
(14) If the Ammeter reads Below 2 Amps… Turn the Test Switch “ON”.
(15) Switch the Ammeter to the Milli-Amps (mA) Scale.
(16) Turn the Green Test Switch Knob to the “OFF” Position.
(17) Measure the Amperage in Milli-Amps (mA). THAT Reading is the Parasitic Draw.

NOTE:
ALWAYS Turn the Green Test Switch Knob to the “ON” Position before Opening the Vehicle Door to Remove a Fuse to Avoid Damage to the Ammeter.

(18) If the Parasitic Draw is TOO HIGH (Above acceptable Limits) Remove One Fuse at a Time until the Parasitic Draw returns to Normal. Refer to the Vehicle Electrical Circuit Diagram(s) to Trace down which components are the cause of the problem.

EDIT: PDF Modified on Wednesday, March 18th, 2020 @ 11:31 PM

I've converted this Instructional to a PDF Document attached below:

 

[Mooseman]

Added to Tech discussion FAQ

 

[mrrsm]

Part 2...

Parasitic Draw Testing: Some Additional Tips​

(1) A Rapid way to calculate ‘...an acceptable Parasitic Draw...’ is to Divide the Recommended Battery Reserve Capacity for your Vehicle(s) defined as (RC) rating by 4:

Example: 100/4 = 25 Milli-Amps (mA) 0.025 Amps

Any Parasitic Draw above this level may require further investigation and Testing.

(2) With the Test Switch turned “OFF”… Place a 10 Amp Fuse via Two Leads across the Test Switch on those Two Brass Pins BEFORE Connecting up the Ammeter. If the Fuse Does NOT Blow once the Test Switch is Turned “ON”, the present Amperage is LESS THAN 10 AMPS. Doing this FIRST can help to prevent overloading your Ammeter or DMM and inadvertently Damaging the Tool.

(3) If the Vehicle supports maintaining the Radio, HVAC Climate Controls, Seats, Navigation Units or other After Market Items, including Computers, Cell Phones, etc, that have SLEEP MODES (Typically involved on 1998 through Later Model Vehicles, Connect a JUMP BOX ...NOT A BATTERY CHARGER to the Positive (+) and the Engine Block BEFORE Performing this Parasitic Draw Test.

(4) Remove the JUMP BOX ...JUST BEFORE performing the Test. This action will serve to preserve the Pre-Sets in Memory and not inadvertently put any of the Computers to Sleep. (Some Computers MAY require up to a few hours to Go To Sleep.

(5) Some GM Vehicles may have certain System Modules working to Wake up Periodically (On-Star, Alarm Systems and Keyless Entry Systems) so if you become aware of this Jump in Battery Power Consumption, those events should NOT be factored in with any actual Parasitic Drain Down.

(6) If the Vehicle has a Retained Accessory Power (RAP) Feature, After taking the Test Drive before Turning Off the Ignition, BEFORE Turning the Ignition “OFF” , Leave the Radio “ON”, Lower the Driver’s Side Window, then Close the Driver’s Door and reach inside to Turn the Vehicle Ignition Key “OFF”. This action will allow the Timer to “Time Out”.

(7) Some Vehicles are equipped with a Switch that Detects whenever the Hood is “OPEN” for the Alarm System to sense possible Auto Burglaries to steal Engine Components/Battery, etc. This Feature MAY prevent the Electrical System from “Going To Sleep”.

This is another Good Resource for investigating Parasitic Battery Drain SPECIFICALLY Using THIS Test Switch and an Ammeter:

www.ls2.com/boggs/Starting/Battery%20Electrical%20Drain.htm

ATTN: @Mooseman…

Thanks for Adding this information to the FAQ… This latest (FINAL) Version contains both Part 1 and Part 2:

 

[WarGawd]

Perfect timing thx This has application to my newer non GMT that I am becoming familiar with since purchasing at end of Feb.

 

[ek02]

I pulled the JX205 splice pack today and jumped the connectors as in the Will Robinson video. I was able to make all modules on that splice pack active by pinging them with the Tech II. I went to the rear splice pack JX306 and was able to ping all those modules to become active. I did not have time today to find out what drew the battery down so I disconnected it. The rain got me. At this point, what are the chances that the BCM is causing all my problems?

 

[mrrsm]

Replied to over on your Original Thread...

SOLVED! - No Crank On 2002 Trailblazer 4.2

It's not the BCM but the VATS module that learns the key cylinder. There are no chips in the keys. As long as the VATS and lock cylinder are still "married", it should still work. If the BCM is replaced, I think it has to learn the VATS module. The PCM security relearn is only for the...

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