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Ground offset

>>From: dak@dpspps.kodak.com (David Kavanagh staff)
>Subject: Re: Heater Fan Leans Out Mixture???

stuff deleted

>Try grounding the meter someplace else (closer to the battery, or on
>a ground that is not shared by high current draw devices).
>This is the same reason the volt meter in the climate control shows
>lower voltages when the fan motor comes on. You really don't drop the
>system voltage by as much as it says, but that ground float accentuates
>the problem...
>	David

David has it right, you are seeing the difference in the ground offset.

The meter takes all its readings with reference to the ground it gets
from the dashboard outlet, which floats ABOVE ground to a greater value
when the heater fan takes more current. The readings are smaller in 
voltage, ( I assume this translates to leaner ).