Alternator

[cbwells]

Hi I have a question If you unhook the battery cables on a Ford f 350 7,3 diesel will it keep running off the alternator mine stops. Thanks Curt

 

[justinray]

Yes, should run forever and ever, so long as fuel doesn't run out.

 

[sassyrel]

Hi I have a question If you unhook the battery cables on a Ford f 350 7,3 diesel will it keep running off the alternator mine stops. Thanks Curt

good way,,to surge and smoke a alt.....

 

[cbwells]

good way,,to surge and smoke a alt.....

I don't want to do that I always thought if the motor didn't keep running the alternator was bad Curt

 

[SparkandFire]

The field voltage to the alternator is extremely unstable without a batter connected to buffer the charge. Hook a voltmeter up and watch what your voltage does with the battery unhooked... (if it will run, some don't)

On a side note, my '85 charging system would allow the engine to run with the batteries unhooked. I found this out by way of the disconnect switch the PO installed without crimping the leads to the crimps very well. With the engine running I accidentally pulled the main lead out of one of the crimps and the truck kept running. I had my voltmeter handy so I checked the voltage on the charge circuit. When you gave it just a little throttle I was able to get almost 20 volts out of it....

On the other hand, my '94 will stop dead cold if you disconnect the battery... My guess is the electronic regulator in the newer 3g alternators has a built in overvoltage protection circuit to protect the alternator.

 

[cbwells]

I tested both batterys and I am getting a reading of over 14 at a idle when I checked the big lead on the alternator to groung I got zero

 

[SparkandFire]

The big lead should always show battery voltage, even with the key off. If the big lead shows 0 volts then the fusible link is likely blown...

 

[cbwells]

Do you have any idea where I should start looking

 

[SparkandFire]

Not sure what year truck you've got, but generally you will have to open the wire loom up and pull the cable out and test it for continuity... It connects to the hot side of the starter relay on the fender.

Or you can upgrade like I did...

You must be registered for see images attach

 

[sassyrel]

Do you have any idea where I should start looking

the fusible link,,should not be far from the fender solenoid.. open the wire harness to find..and replace it,,with a regular style fuse..napa and others have them,,in high amerage configurations...fusible links suck.........

 

[cbwells]

Ok Thanks

 

[icanfixall]

Man o man that an upgrade line to the alternater right there. No voltage drop in that line... Many years ago cars and trucks had genersters instead of alternaters on them. So if the battery was not good enough to start the rig and you had a standard trans. Just a push would get you going. Now with an alteranter you need voltage to make the field function. You just can't push start an alternater rig unless you have some voltage in the batterys. This is why our idi in a standard trans application is the best dooms day rig. All we really need is to make a manual fuel shutoff valve on the injection pumps and we can run till hell freezes over.

 

[cbwells]

What size wire is that It looks good

 

[SparkandFire]

I want to say it's about 4 AWG, but I would have to check the box to be sure...

 

[cbwells]

I am doing that upgrade Thanks