[DeTomaso] Electrical questions--HELP!

[Thomas Tornblom]

Christopher Kimball skrev:
> This is amazing and seems counter-intuitive to me--when I hooked up the 
> fan relays' main power, I purposely went directly to the positive 
> terminal of the battery (as I did with the main stereo amplifier's power 
> cable precisely so I would (I thought) avoid the car's electrical system 
> completely.
> 
> I took electronics in college a LONG time ago, and my memory is fuzzy 
> these days, but if the fans are grounded directly to the frame (as they 
> are now) and the power is going to the fan motors directly from the 
> batery's positive terminal (which it is), how can the ammeter even be 
> involved in the circuit?

Because the power to all these things comes from the *alternator*, not 
the battery, when the engine is running. The only way for the current to 
get from the alternator to the consumers is through the ammeter, which 
will indicate that current is flowing in the direction to the battery 
(== charging).

If you instead take the power on the alternator side of the ammeter, 
this current is fed from the alternator to the consumer without having 
to go through the meter, and the meter will not indicate that it is 
charging, which is correct.

It will also correctly indicate that the battery is draining if you run 
these things when the engine is off, as the only way for the power to 
get from the *battery* to the consumer is through the ammeter in the 
other direction, and it will indicate a discharge.

The only current that should flow through the meter is, as SOBill said, 
the power going into or out of the battery.

> 
> I'm not questioning that you are correct, I just need to understand what 
> I'm missing!

I hope the simple explanation above will help you do that :-)

You are not alone in your thinking.

> 
> Thanks
> 
> Chris

Cheers,
Thomas

> 
> 
>> From: SOBill at aol.com
>> To: Thomas.Tornblom at hax.se, chrisvkimball at msn.com
>> CC: detomaso at realbig.com
>> Subject: Re: [DeTomaso] Electrical questions--HELP!
>> Date: Sun, 29 Apr 2007 13:59:43 EDT
>>
>>
>>
>> Thomas is absolutely correct.
>>
>> The ammeter is intended to only show the current flowing into or  out 
>> of the
>> battery.
>>
>> If you connect a load on the battery side of ammeter, the  current coming
>> from the alternator to supply that load will cause the ammeter to  
>> erroneously
>> indicate a charging current going into the battery.
>>
>> All loads in the car should be connected to the terminal of the  ammeter
>> which comes from the alternator so that only charge or discharge  
>> currents from
>> the battery flow thru the ammeter.
>>
>>
>>
>> In a message dated 4/29/2007 2:00:02 AM Pacific Daylight Time,
>> Thomas.Tornblom at hax.se writes:
>>
>> Do you  have any consumers connected directly to the battery instead of
>> through  the cars wiring?
>>
>> The new fans perhaps?
>>
>> If so, then any current  these consumers are using will have to go
>> through the ammeter and it will  indicate that it is charging the
>> battery, when in fact the current goes to  the consumer instead of to the
>> battery.
>>
>>
>>
>>
>>
>> SOBill  Taylor
>> sobill at aol.com
>>
>>
>>
>> ************************************** See what's free at 
>> http://www.aol.com.
> 
> 
> 
> !DSPAM:46351d8b290502457613276!
> 


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