Strange issue when starting - smoke from under dash

Thread Tools
 
Search this Thread
 
  #11  
Old 12-31-2014, 11:23 AM
z28pete's Avatar
Tech Droid
Join Date: Aug 2005
Location: North East PA
Posts: 9,215
Default

Originally Posted by 1971BB427
Very good point! If the car has a low voltage scenario, all the amperages, and resistance will go up.
Wow, looks like a new law of physics has been discovered. lol

According to Ohm's law--- Voltage (E) = Current (I) x Resistance (R)
Therefore:
E= I x R , or I= E / R, or R = E /I

Voltage does not change resistance, but resistance can change voltage, but only if there is a current flow.

Lower voltage always causes less current flow (amperage)
 
  #12  
Old 01-01-2015, 10:25 AM
1971BB427's Avatar
Second Generation Moderator
Feb 2010 ROTM winner
Jan 2013 ROTM winner
ROTM Winner's Club
Join Date: Aug 2008
Location: Portland, Or
Posts: 9,097
Default

Originally Posted by z28pete
Wow, looks like a new law of physics has been discovered. lol

According to Ohm's law--- Voltage (E) = Current (I) x Resistance (R)
Therefore:
E= I x R , or I= E / R, or R = E /I

Voltage does not change resistance, but resistance can change voltage, but only if there is a current flow.

Lower voltage always causes less current flow (amperage)
Afraid not. Lower the voltage, the higher the amperage. Higher resistance will indeed cause the voltage to also drop, and that's why as you get longer wire lengths, you get more resistance, and need to go up in wire gauge as you go longer in length.
If you use ohm's law you'll see that for example, 1,200 watts at 120 v. is only 10 amps, but at 12 v. it's 100 amps. Thus less voltage is indeed more current or amperage.
I only did this for 35 years before retiring, but it's been over 4 years, so maybe I'm rusty.
 
  #13  
Old 01-01-2015, 11:18 AM
z28pete's Avatar
Tech Droid
Join Date: Aug 2005
Location: North East PA
Posts: 9,215
Default

You are confusing the issue with output power. Yes, you need more current to get the same power if the voltage drops, but the only way you are going to get increased current with a lower voltage is to lower the resistance. Resistance in a circuit is more or less a constant than can only be physically changed. I spent 35 years designing and repairing CO power systems for AT&T, and still doing consulting work for them, but regardless of "qualifications", the equations for power are: Power (Watts)= Current squared / Resistance , or Power = I X E, or Power = square root of So if the voltage is lowered then current must be increased to keep the same power, but this won't happen unless the resistance is lowered.
May want to look at the Engineering Tool Box
Ohm's Law
 

Last edited by z28pete; 01-01-2015 at 11:21 AM.
  #14  
Old 01-01-2015, 09:10 PM
1971BB427's Avatar
Second Generation Moderator
Feb 2010 ROTM winner
Jan 2013 ROTM winner
ROTM Winner's Club
Join Date: Aug 2008
Location: Portland, Or
Posts: 9,097
Default

I guess I can't see what the argument is? You're talking power, and I'm talking current as it relates to operating voltage. I never put power into the equation, as I'm simply stating the facts as voltage, current, and wire size are related to each other, and resistance.
Are you disagreeing that a lower voltage for equal watts results in a higher current, and larger wire size? Something tells me you're an engineer.
 
  #15  
Old 01-01-2015, 09:54 PM
z28pete's Avatar
Tech Droid
Join Date: Aug 2005
Location: North East PA
Posts: 9,215
Default

I agree that lower voltage for equal watts requires more current, what I am trying to say that if voltage is lowered and the circuit resistance is not changed, then lower voltage will cause the current to go lower proportionally, which also results in lower watts.
Anyways, let's forget the whole argument. lol
 
  #16  
Old 01-01-2015, 10:14 PM
1971BB427's Avatar
Second Generation Moderator
Feb 2010 ROTM winner
Jan 2013 ROTM winner
ROTM Winner's Club
Join Date: Aug 2008
Location: Portland, Or
Posts: 9,097
Default

Good idea. I quit talking electricity when I retired 4 years ago.
 
  #17  
Old 01-01-2015, 10:17 PM
Camaro 69's Avatar
Senior Moderator
January 2010 ROTM Winner
Join Date: Oct 2007
Location: The 'Burbs of Chicago
Posts: 18,306
Default

Oh, you guys! If the poor OP wasn't corn-fused before, he sure is now. lol
 
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
phoenix901223
93-02 General
15
06-07-2012 07:01 AM
MIKESIN
93-02 General
1
01-28-2009 05:59 PM
MIKESIN
Computer & Fuel Systems
3
01-28-2009 05:57 PM
MrTasty95
93-02 V6 Tech
5
12-07-2006 11:49 AM
MartynCZV6
93-02 V6 Tech
4
04-10-2006 05:11 AM



Quick Reply: Strange issue when starting - smoke from under dash



All times are GMT -5. The time now is 03:25 AM.