Ford Muscle Cars Tech Forum banner

1 - 11 of 11 Posts

·
Registered
Joined
·
1,233 Posts
Discussion Starter · #1 ·
I put my battery in the trunk yesterday. Before I swapped the alternator out I checked to make sure everything was O.K., I pulled the + terminal on the Battery while the car was running and it kept running. Good, now I'll install the new 1 wire alt.

I put it in, Removed the original wiring (3 alt wires, 1 wire that went to the + side of the solenoid, and the ground wires). I installed the new 1 wire unit, ran a 4 guage wire to the + side of the battery cutoff switch. I start the car and remove the + battery terminal and it goes dead.

The other side of the battery cutoff switch is connected to the positive side of the solenoid, so this is no different than if I ran a wire straight from the alternator to the solenoild.

What did I miss? Did I need one of the original wires? Is the alternator possibly not grounded and does it need to be? How can I check with a voltmeter?
 

·
Registered
Joined
·
1,233 Posts
Discussion Starter · #2 ·
Nevermind, apparently you have to reach a certain amount of rpm in order to activate the alternator. It works now.
 

·
Registered
Joined
·
3,692 Posts
Indeed they have to reach a high enough rpm to self excite.
 

·
Registered
Joined
·
1,604 Posts
You should NEVER disconnect the battery while the engine is running! It causes a condition called Load Dump and can damage the regulator and diodes in the alternator.
 

·
Registered
Joined
·
2,617 Posts
From my experience with a Powermaster 2G alternator, it's about 1200-1500rpm. Seems like it starts up at a lower RPM if the vehicle has recently been ran, I dunno if it's because the battery has a little higher residual voltage or what.
 

·
Registered
Joined
·
3,692 Posts
On 2007-01-08 06:05, bmcd66250 wrote:
You should NEVER disconnect the battery while the engine is running! It causes a condition called Load Dump and can damage the regulator and diodes in the alternator.
An interesting thing about your theory is you're assuming the ALT is charging the batt, when in fact it might not be, so in all actuallity the batt may or may not be a load on the charging system.





So you're saying I also shouldn't unhook a set of jumper cables from a car I attempted to start until I turn off my engine? Yeah, that 's gonna happen.



BTW wouldn't turning the headlights off damage the ALT as well?
 

·
Registered
Joined
·
1,604 Posts
First of all, it's not theory, it's fact. Talk to someone who understands automotive electrical systems. The battery acts like an electrical "shock absorber" for the alternator as the electrical loads for the car are constantly changing. Additionally, the output of an alternator is not a pure, level DC, there's a lot of ripple to the waveform. The battery helps smooth that much the same as a filter capacitor does on an electronic power supply. In your example of using jumper cables, when the cables are attached, the battery of the vehicle that's doing the jumping is now connected to your car and buffering the load. I used to work as a test engineer at a company that built automotive electronic equipment. It was always a challange to take in to account all of the strange things that can happen in an vehicles electrical system. Things aren't as cleaar-cut as when designing battery-operated or house AC-operated devices.
 

·
Registered
Joined
·
9,251 Posts
1 - 11 of 11 Posts
Top