I read some instructions in a car factory manual for a battery drain test. It says to put a jumper in parallel to the ammeter between the disconnected negative cable and battery post. Wouldn't that defeat the purpose of the ammeter and not give any useful reading? Am I misunderstanding something?

4. Connect a fused jumper wire (30A) between the negative battery cable and the negative battery post to prevent modules from resetting.

5. Disconnect the negative battery cable from the negative battery post without breaking the connection of the jumper wire.

6. NOTE: It is very important that continuity is not broken between the battery and the negative battery cable when connecting the meter. If this happens, the entire 40-minute procedure must be repeated.
Connect the battery tester between the negative battery cable and the post. The meter must be capable of reading milliamps and should have a 10-amp capability.

 

Uh... if you want us to comment on steps 4 through 6, how about telling us, exactly, what steps 1 through 3 say.

What is the "jumper" that is being discussed?

What is the "battery tester" that is being discussed?

 

Oh, bugger, my mistake, I overlooked where in the next couple of steps it says to disconnect the jumper. The jumper is meant to be a temp connection.

The jumper is as-stated - just a fused wire.
The batter tester is an inline ammeter.

Sorry about the bogus post. The moderator can delete this thread!

 

Glad you figured it out. No need to delete the thread. The forums are archival in nature and someone else may have a similar problem ten years from now and be searching for help, stumble upon this thread, and figure out their confusion in the process.

 

Oh, bugger, my mistake, I overlooked where in the next couple of steps it says to disconnect the jumper. The jumper is meant to be a temp connection.

The jumper is as-stated - just a fused wire.
The batter tester is an inline ammeter.

Sorry about the bogus post. The moderator can delete this thread!

My guess, and just a guess, is to prevent the hook up transients from blowing out the meter. The meter then just has to handle the steady state current.

 

My guess, and just a guess, is to prevent the hook up transients from blowing out the meter. The meter then just has to handle the steady state current.

No. It explicitly states that it is needed to prevent modules from resetting and also states that if current is interrupted, the entire 40 minute test must be repeated.

 

No. It explicitly states that it is needed to prevent modules from resetting and also states that if current is interrupted, the entire 40 minute test must be repeated.

Oh ok, thanks for clarifying that. Funny I read that part too.

The reason I gave is also typical, but probably not for this particular test.
The kit I bought long time ago before OBDII crap had a shunt with a bypass you could rotate and tighten the bolts so that it shorted out the shunt.
Geeze, I hate to think of how long ago that was now ha ha. Someone I knew needed it to test their car, and I never saw that kit again