RE: [DML] Fan Speed Overload - Technical Correction

["John Hervey" <john@xxxxxxxxxxxxxxxx>]

Dave, As much as I respect your comments, the blower motor CB was 25 amp
original. I use a 30 amp just to allow a little more for age, but I feel 40
amps is trying to cover up a problem that the motor needs to be replaced. 40
amps will allow the wires to get hotter than they already are and will cause
damage. 
Throwing higher current fuses or CB in a system to try to fix the problem to
me would just be adding to the problem. 
You could do that with the fuel pump fuse, low beam head light fuses and
burn up the fuses box even faster.
My comments.
John Hervey
www.specialtauto.com
www.deloreanautoparts.com

    

-----Original Message-----
From: dmcnews@xxxxxxxxxxxxxxx [mailto:dmcnews@xxxxxxxxxxxxxxx] On Behalf Of
doctorDHD@xxxxxxx
Sent: Saturday, May 19, 2007 6:01 AM
To: undisclosed-recipients:
Subject: [DML] Fan Speed Overload - Technical Correction

 
 
Sometimes I read something that comes to the right conclusion but is just
is 
not correct technically and this is one of those times, so in the interest
of 
 correctness ...
 
If the resistance of a circuit INCREASES then the current in that circuit  
will actually DECREASE.  Current = Voltage divided by Resistance.   (This is
the 
famous Ohm's Law)
 
So while the below mentioned circuit breaker may likely be the problem, and

perhaps it is the connections at the circuit breaker that are building up
too  
much resistance,  it would NOT cause too the circuit to draw more  current.

It actually would be less!
 
However, that being said... the increased resistance of the poor connection

would cause more power to be lost at the connection, Power = Current²  
(squared) times Resistance.  Since this lost power will turn into  heat, it
certainly 
could cause the circuit break to open the circuit.
 
Since the resistance of the connections is just a small fraction of the  
total resistance of the circuit, even if the contact resistance doubled the

current would not drop much but the power lost (heat developed)  would rise
by 
about 4 times  (doubled ie 2 squared = 4).
 
Any comments on my math?
 
Of course if the blower motor was going bad and ITS resistance was  too LOW 
(ie its windings partly shorting out) then that Would cause too  much
current 
to flow in the circuit which could also open the circuit  breaker....
 
Check the connections and make sure you have the upgraded ?40 AMP  breaker.
 
Now back to your regularly scheduled program....
 
Dave Delman
 
D² & 06530 + 2700 ohms



Craig,

I have the same issue with my DeLorean although  my blower motor usually
cuts 
out on a hot day in traffic after about 10  minutes.  There is a circuit 
breaker for the blower motor.  I would  guess that perhaps your blower motor
is 
pulling too much current.  Have  you checked your connections to make sure
they 
are clean so you aren't  building up too much resistance, and thus drawing 
more  current?







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