Electrical Short Troubleshooting Help Needed

in_ohaio · Oct 29, 2017

We have an '06 Ody with 202K miles. With the cold wet weather, cranking the van was a little labored. The battery was at 12.1V so I charged it overnight. The starts were quick like usual.

My son drives the van and the other day it was hard to start again. When it finally did, it sputtered a bit. One block down the road, the VSA and ABS lights flashed on. He had the presence of mind to turn back into the parking lot where it completely died.

I went to rescue him with my trusty voltmeter. It read 0.0V with the battery cable attached. When I disconnect the ground cable, the battery read around 4V. Thinking it's a bad battery, I tried to jumpstart it. With the other vehicle running, the voltage drops from 13+V to around 9V and the van doesn't start. Turns out there is a short between the Pos and Neg cables.

I had it towed and am waiting for the Honda dealer to open up tomorrow to see what they say. Does anyone know what type of short could happen that quickly and pull so much power? I've read about the alternator as a possible cause but that thread never followed up with the solution.

Is there hope for a quick fix or do these types of problem cost a lot to troubleshoot?

Thanks for any insights!

John Clark · Oct 29, 2017

How did you determine there is a short between the pos and neg cables?

in_ohaio · Oct 29, 2017

I used the continuity function on the multi-meter with the probes on the disconnected terminals.

John Clark · Oct 29, 2017

There is always "continuity" between them. A "continuity" check is not really a valid check for that. Did you measure the actual resistance in ohms between the two terminals?

in_ohaio · Oct 30, 2017

Sorry for the late response. I've been helping my son with his college application essay...what a headache.

Hmmm, Is that why there is always a small drain on the battery? I think that makes sense now that you point it out.

No, I didn't go far as to measure the resistance. Checking continuity is the extent of my troubleshooting skills and evidently it's not that good.

John Clark · Oct 30, 2017

The continuity check (and even resistance check for that matter) puts such a small current through the circuit that just a running clock can cause it to show continuity. Believe it or not, in most cases the ohm meter has little use in electrical troubleshooting. It's useful for some things here and there but that's about it.

I would guess that either the battery is worn out or there is something draining the battery when the key is off. There are any number of common things that can do that, i.e. AC compressor relay fails closed, power sliding door latch switches failed or failing. I'd check the health of the battery and replace if necessary. Once that's done I'd check for any parasitic draw on the battery with the key off.

marvinstockman · Oct 30, 2017

How old is battery?

in_ohaio · Oct 30, 2017

The battery is over 5 years old. Apparently I got a good one.

I will replace it if the dealer can fix the main issue of the large current draw. Rereading what I originally wrote, I didn't make it clear that the voltage drops from 13+V to around 9V with the key off.

in_ohaio · Oct 30, 2017

The dealer said it's a bad alternator that eventually killed the old battery. It'll cost $550 to replace with an aftermarket alternator and a new 100-mo battery. I guess that's not too bad to keep the van running for a little longer.

John, thanks for the lesson on continuity. You are right, the multimeter lead me astray.

Electrical Short Troubleshooting Help Needed

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