[ihc] Humphrey's Coil Voltage

[Joel M Brodsky <jmbrodsky@xxxxxxxxxxxx>]

George,
If you are measuring from one side of the coil to the other, then you are
measuring the voltage drop across the coil.
The remaining voltage would be something like 12 - 4.2 , or 7.8V for you to
power your solenoids.
I'm not sure what you have in your truck or how it's set up, but measuring
each side of the coil, to ground might give
you a better understanding of what the voltages are and where they are
going.
Remember that a device requires 'juice' to work, and depending on how it's
all set up it can draw down the voltage, the current or both.
It all depends on the situation.

JoelB
                                                                            
                                                                            
                                                                            
                                                                            
                                                                            
                                                                            
                                                                            
   Date: Fri, 19 Mar 2004 13:37:00 -0800                                    
   From: George B Humphrey <xgbhx@domain.elided>                                 
   Subject: [ihc] Coil Voltage?                                             
                                                                            
              I want to use the positive side of the coil as the trigger    
   for the                                                                  
   relay                                                                    
   to the Projection system. I'm not getting enough current to the fast     
   idle                                                                     
   solenoid during start up and the solenoid recoils during cranking. I     
   tried setting it up this way and can not get it to work at all. The      
   fuel                                                                     
   pump won't even prime. I checked the voltage across the coil (Pertronix  
   Flame Thrower) while the ignition is in the start position and the       
   engine                                                                   
   is not running and only get 4.2 volts. I assume I should get full        
   voltage. Is that correct? If so, does anyone have an idea why I am not?  
   Once started the 345 runs beautifully. If 4.2 volts is about right,      
   what                                                                     
   do I need to do to get the Projection to trigger from the coil? As you   
   can tell my auto electric knowledge is only slightly above none at all.  
                                                                            
   George H.                                                                
   72 Scout II                                                              
   345 V8