OK, here are the results of the tests.
With engine running, laptop plugged in and running in the rear outlet: Battery: 13.5 Rear outlet (feed-through plug): 12.7 Front outlet: 13.5
Same as above, but with heater fan on full and headlights on: Battery: 13.45 Rear outlet (feed-through plug): 12.5 Front outlet: 13.35
Chassis ground voltage drop test (with everything running as per above two):
0.057
With VM connected to battery positive and rear outlet fuse: 0.033
With VM connected to rear outlet fuse and center of inverter feed-through plug in rear outlet: 0.69
With VM connected to shell of inverter feed-through plug in rear outlet and body ground: 0.164
So, the results seem to be accurate, since the total of the four tests =
0.94, which is the same as the drop from the battery to the rear outlet.
What seemed strange to me, though, is that these tests don't show a big drop to the front outlet. Yet I have intermittent problems with the inverter staying on in the front outlet when the engine is off.
Plugging the inverter/laptop combination into the front outlet, with the same conditions as above, I got: Battery: 13.45 Inverter feed-through plug: 12.9
So, not as much of a drop as to the rear outlet, but still a drop (though it didn't show up when I just tested the front outlet without the inverter plugged in).
Anyway, thanks for your comments regarding the above!
Neil
>
>>> It is something else. DC likes to save money where it can and they >>> probably
>>> didn't expect something that can draw 11+ amps and be sensitive to >>> voltage
>>> drops to be plugged into that outlet and based the wire size on how warm
>>> they will get at full rated current, not on voltage drop. While there >>> is
>>> a
>>> slight chance that replacing the battery will correct the problem, it >>> will
>>> be a temporary solution. There could also be a voltage drop caused by a >>> bad
>>> chassis to body ground but that is probably only adding to the >>> undersized
>>> wires.
>>
>>I tend to think it's the latter. The front outlet is also problematic. >>
>>> You are looking at it from the correct perspective and hopefully learned >>> a
>>> little about electrical tracing as well.
>>
>>Yes, indeed! I appreciate everyone's help. I was able to do it with my
>>14-year old son, so we both learned a little and had fun (most of the time
>>:-) ) at the same time.
>>
>>> The problem IS in the wiring and
>>> rewiring the front outlet is really not that big of a deal and just >>> about
>>> anyone that has installed a car stereo could do it. Good luck with >>> whatever
>>> decision you make.
>>
>>If there are problems with both the front and the rear outlets, wouldn't >>it
>>make sense that the problem is elsewhere besides the wiring to each >>outlet?
>>
>>Neil
>>
>>
> Neil, are both outlets on the same fuse like on my Pontiac?
> If not, there is a simple way to find out if you have a common problem
> (affecting both) or whether it is simply a matter of both circuits
> having a problem. With the engine running, so HOPEFULLY the inverter
> will stay running, and with the inverter in the back plug, with the
> computer on, check the battery voltage at idle.
> Then check the voltage at the inveter feed-through plug, and then at
> the front plug. The front plug SHOULD read battery voltage, and the
> rear feed-through plug will read less.
>
> The difference between battery voltage and feed-through plug voltage
> is the total voltage drop. If the battery voltage and the front socket
> voltage are not the same, the difference is the voltage drop that is
> common to both circuits (could be ground resistance, could be power
> feed resistance to the fuse panel)
>
> Turn on the heater fan and / 0r headlights and see if the voltage drop
> increases. Make sure to recheck the battery voltage so you can
> accurately calculate the circuit voltage drop.
>
> Now do the chassis ground voltage drop test again (2 volt scale from
> battery post to the good chassis ground).
>
> Do this test with the same load (computer and headlights and/or heater
> fan). Subtract this drop from the total drop and you know how much
> drop you have un accounted for.
> To find out where the drop is occurring, connect a wire from the
> battery positive to one wire of the meter, and connect the other wire
> to the fuse in the fuse panel. You will need a "jumper" wire to extend
> the voltmeter leads from the battery back to the fuse box. Whatever
> the voltage reading is from the battery to the fuse is the voltage
> drop between the battery and the fuse block.
> Then you can go from the fuse to the center of the feed-through plug
> on the inverter. Any reading here is the voltage drop across the
> (thin) wire from the fuse to the inverter plug. Then connect the meter
> from the shell(ground side) of the feedthrough plug to a good body
> ground (can be any bright plated screw or bolt into the metal body -
> often the tailgate latch is as good and handy as any) ANY reading here
> is drop between the plug ground and body ground.
>
> Reply with the results of the test, or if you want to avoid the
> "circus" you can respond to me by e-mail. I think you can figure out
> my email address from the munged address shown.
>>>
>>>
>>> --
>>> If at first you don't succeed, you're not cut out for skydiving >>>
>>>
>>
>
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