1998 Grand Caravan

Page 11 of 13  


me,
Not necessary and it has no way to know what is plugged into it.

And you have proof of this where???

And you base this on what? We are talking about a factory battery here and a DC at that.

No, it indicates a high drop in the wiring and a small drop from the battery.

And would not be able to start the car and like magic, it still does, even after the load test. I guess that's strike 5.

the
Of course you are in agreement. You two are about the only ones that agree with each other on most issues because like this one, you are W R O N G ! ! !
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Max Dodge wrote:

You are really into this revisionist thing aren't you? None of us said that there was no reason to determine the voltage at the battery. We simply said that wasn't the most logical place to start troubleshooting. You seem to lack logic as well as common sense.

And, likewise, you should go back and read what we really wrote. You won't find a statement that says that there is no reason to ever test the battery voltage.
Matt
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the
and
Just because you keep saying it doesn't make it any more true. THE BATTERY WAS LOAD TESTED, despite your constant denial of such!!!!
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Except I suggested a load test, not simply dropping probes on the posts and saying, "wow, its got 12v+, it should be ok!!"
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Max

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Max Dodge wrote:

Good God, Max. I'm not going to go back and re-trace the whole freakish thread, but my recollection of the assertions made is NOT what you said above. What was said is that knowing what we know about the whole car, (including that it started normally and that wiring to cigarette lighters and auxiliary outlets tends to be under-sized) that the *FIRST* thing to do is probably *NOT* remove the battery from the vehicle and take it somewhere to have a load test on it. The FIRST thing that makes sense for a guy with a garage and a voltmter is just measure the voltage drop, under load, between the battery and the cigarette lighter. Whether the battery is fresh as a daisy or half a volt down from where a new battery would be is less important than whether or not you're losing 2.3 volts between the battery and the cigarette lighter!

You didn't say that. The idiot who started the anti-engineer tirade said that.
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Then your recollection is faulty.

Given that removal of the battery is not necessary, and that a load test is a simple two minute (includes time to remove tool from storage and stow it again) test, It most certainly IS the first test a tech should do, since the rest of the diagnosis involves creating a load at the port. But, given that the load (an inverter) at the port ALREADY indicated a low voltage condition AT THE PORT, the next place to check is... the battery. So you are advocating ANOTHER check of the obvious, before proceeding to check the variables?

Except that we already know from what the inverter did that the voltage is low. No need to check again.

How do you know you are losing 2.3 volts if you haven't checked the battery under load? Maybe the entire system, including the battery, is dropping that 2.3 volts. As I said in a previous post, the only way you are losing that voltage without popping a fuse is if the battery can't supply the voltage. Unless you are willing to agree that there is a significant hazard in the wiring catching fire, which would be an engineer's fault for not spec'ing the right wire guage.
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Max Dodge wrote:

It is if you're just a weekend mechanic.

Why is it low at the lighter? Is it low because the battery is somehow sagging under a few amps of load, yet still can supply 100+ amps to crank the engine? (Not bloody likely!) Or is it because there's an excessive voltage drop along the supply to the lighter or perhaps a bad ground?

Easy:
1) plug in the inverter 2) measure the voltage at the battery. Call it "v1" 3) measure the voltage at the cigarette lighter. Call it "v2" 4) subtract v2 from v1. If the difference is a couple of volts, then you know that there's excessive voltage drop and THAT is why the inverter is cutting out.

I can't help it if you're just dead-nuts wrong. What's going to pop the fuse if there's an undersized wire that is dropping the voltage? Or a bad ground connection? When those faults occur, the fuse winds up carrying LESS current than it should and is LESS likely to pop.

I think that's EXACTLY the problem in this case. Or a connection has deteriorated with time. In cars that have real cigarette lighters and not just "accessory outlets," its not at all uncommon for the center pin of the outlet to become corroded due to cigarette ashes transferred from the lighter and the heat of the lighter when its in operation. Sometimes the weak connection is the lighter socket ITSELF.
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No, it is not. For as educated in this as you all claim to be, you don't seem to realize that a load tester is easily found and under $50. Thus many places have them, and loan them out. All you need to do is clamp them on and push a button, no need to move the battery anywhere.
An example seen here:
http://www.toolsource.com/ost/product.asp?sourceid=overturebattery%5Ftest&dept%5FidP0&pf%5Fid 095&mscssid=X0JEU6MD7P9K9KLGDBJM2VJPUSAM2889

1) See my reply to Bill regarding the very real possibility that the starter works fine while the power port may not.
2) The only way to determine if its the wiring or the battery is to load test the battery.
3) testing the ground could easily be more difficult than testing the battery.

Alright, if you plug in the inverter, and you place a load on the battery via the port, what have you done? Yup, thats right, LOAD TESTED the battery. And on top of it all, you haven't removed the battery. Jeez, that was tough.

Yup, thats why I prefer to load test the battery. Then I can see how the battery works under load without all the rest of that stuff as variables. Testing the battery determines a baseline, and allows for proper testing of the rest of the varibles.

Terrific, see above regarding the ease of each test and why a battery load test is so simple.
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This would be effective if we didn't already know there was a difference in voltage via the inverter function.

You'll find nothing here, since both are grounded. Assuming the socket is losing its ground, you'll still find nothing. If you measure the resistance, THEN you'd find a bad ground.

The downside to these tests is the fact that most multimeters do not have leads long enough to complete the desired circuit. Aside from that, it would be a very effective method of checking the circuits. However, it does not determine if the voltage drop under load is due to wiring or battery.
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you
is
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Right, so are you measuring the voltage or resistance in the wire and its cobbled connections or the actual circuit you intended to check?

Right, but you did not say that before, so now you are doing a load test, something that the "experts" say isn't necessary.

Thats great, but the "negative" side won't have any power. So testing for voltage will net you a zero. If you wish to test the ground side for continuity to ground, a resistance check is in order.
Fact is, there are about ten ways to check each side of the circuit. The best way with the opening facts given is to check your power source for voltage and voltage under load, and see how it compares to your power port. That will eliminate the battery or the wiring. IF its the wiring, as is widely suggested (what engineer would allow THAT??) then a continuity check on the ground side is in order. If that proves to be good, then rewiring the port is the next step.
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inverter
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On a power port with nothing plugged in, there is no power on the ground side.

If the ground wire is to connected load which is in turn connected to a power source, that is correct. In the case of a power port with nothing plugged in, you will get NO voltage reading on the ground side.

I would, but without a battery, I know what I would find. NO voltage. This circuit would only have voltage if you had a battery or Uncle Fester connected to it.
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Max Dodge wrote:

Damn! Here is what you said: "However, it does not determine if the voltage drop under load is due to wiring or battery."
Then Christopher: "yes it does max. if you have a load connected so the circuit is complete then measuring from the outer shell to neg post should result in 0 volts (or nearly) same with positive post to center post (you'll have to back probe as a load needs to be connected to complete the circuit.) now using ohms law we know that if there is resistance in either of the pos or neg side of the circuit you will see a "voltage drop" meaning you will read a voltage acrost that resistance. if the voltage is 0 then that means the resistance is 0."
Once again, you are proving your lack of understanding of Ohm's law and your dishonesty in the discussion (or intelligence - again, sometimes it's difficult to separate the two).
Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')
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Once again, when someone changes their description of the test, it changes the method of testing. Chris changed from simply probing the port to back probing the plug of the device plugged into the port.
Two entirely different things get two entirely different results.
No lying, except on your part, where you fail to observe the difference in Chris' posts.
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i never changed my post or method. read again max
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In the first post you said to probe the center pin of the socket, clearly, if you wish to do that, nothing will be in the port. In your revision, you mention that back probing the plug would need to be done, since you've got a "load" plugged in.
Now, either you are doing a load test which is against all the "informed" opinion, or you are testing for continuity, not voltage, on the ground side.
Go back and read what you claimed again, or better yet, follow your sage advice and stop posting.
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Max Dodge wrote:

Back when I worked as an electronics tech, if someone told me to "probe the center pin of socket # such-and-such under load," it was UNDERSTOOD that I would gain access to the back of the socket and "probe" the voltage at the center pin's back connection, NOT stick a probe down the socket itself. And today when I ask a tech to do that same measurement, they still understand the method to use, so terminology hasn't changed either.
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Great, well, then explain this:

Ken suggests one type of test, then Chris suggestes another. My reply was to Ken's description, not Chris's alteration for his use. Obviously the operative term "under load" was missing in the first description.
Funny part is... theres that load test again. If its so unnecessary, why does it keep coming up?
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Max Dodge wrote:

Your sleight-of-hand on that is (and surely you know this - and I'll quit calling you Shirley) that in the context of car batteries, the term *load test* implies something other than putting a relatively low level current and reading voltage (or, the equivalent, a continuity test with an ohmmeter) for a negligible amount of time for an instantaneous reading to register wiring drops.
A load test is sucking a certain amount of energy (watts x voltage x time) out of the battery (excluiding the wiring) by applying a fairly heavy current for a prescribed time while monitoring it's voltage to get an idea of capacity - not just its steady state resistance.
The test that was being talked about was to test voltage drop in the wires. Your much earlier rantings were clearly about traditional "load testing the battery" itself - not about hi-resistance cable clamp connections - not about what are low level instantaneous tests of the wiring with low level currents - the effects on the battery of which are going to be negligible. Those are low level current tests (simply applying a light short-term load/current in a broader sense outside the narrow context of battery load tests), a load test of the system with negligle implications about the battery itself), but, for honest discussion, not the proverbial *battery load test* that you started out talking about 200 posts ago.
So stop the shell games por favor.
Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')
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