Alternator question

[J_J]

The field has to have the current flow from the battery to generate the field for the stator.

 

[Soundguy]

Did either of you even bother to read the original post?

The issue is whether the alternator can be expected to continue to produce current when the battery is removed with the engine running.

Probably not.

I'd also like to point out that the 2nd fastest way I know to KILL an alternator is to unload it while it is turning.. I.. disconnect the battery.

that said.. to the OP what alt model are we dealing with?

that will help with diagnosis.

soundguy

 

[Soundguy]

The field has to have the current flow from the battery to generate the field for the stator.

not always. you can get 1 wire regulators that will bootstrap their own field current once the alternator is spinning fast enough. same principle as an old a or b circuit genny and external reg.. residual magnetism in it's field pieces generates small current on armature.. which is fed to field.... etc..

I don't prefer 1 wire setups like that.. they usually require something ridiculess like 1800 rpm to self excite... plus they typically cost more. I much prefer the ulti wire alts that have an excite circuit, and external voltage sense.

soundguy

 

[crazyal]

I just want to second the warning that disconnecting your battery while your engine is running can harm your diodes inside the rectifier. The best way is to turn the key on, measure the battery voltage with a good multimeter(before starting the engine) and then after starting the engine. You should see an increase in voltage with the engine running.

 

[Richard]

Sorry late in getting back.

What type alternator? I don't really know. I CAN say (as useless as I know this is going to be) it "LOOKS" like a typical General Motors style that I might have had on my 1971 442. I don't recall if the regulator is integrated or not.

I'll do the voltage check thing this weekend. As for possibly hurting a diode or two by lifting the battery switch while running.... too late :ashamed:

However, it was done after this problem (annoyance) has persisted so if I blew anything, I probably only added to an existing problem. What really stinks is the only place I know of to take it is probalby 30 miles from work... AWAY from the direction where I live and I already drive 25 miles to work.

yeesh....

Interestingly, my rear work lights (flood lights mounted on the top of the cab for backhoe use) stopped working maybe 2 years ago. I've been wondering if the switch is bad since the fuses seem to be ok.

Maybe this will be a good excuse to run some of those problems down as well. It sure is nice having the rear floodlights every now & then.

 

[Soundguy]

post a pic of the alternator, especially back, and of any connectors on it. note any writing, especially at the connector locations.

soundguy

 

[J_J]

Soundguy is right. Maybe this will help.

FIELD EXCITATION

When a dc voltage is applied to the field windings of a dc generator, current flows through the windings and sets up a steady magnetic field. This is called FIELD EXCITATION.

This excitation voltage can be produced by the generator itself or it can be supplied by an outside source, such as a battery. A generator that supplies its own field excitation is called a SELF-EXCITED GENERATOR. Self-excitation is possible only if the field pole pieces have retained a slight amount of permanent magnetism, called RESIDUAL MAGNETISM. When the generator starts rotating, the weak residual magnetism causes a small voltage to be generated in the armature. This small voltage applied to the field coils causes a small field current. Although small, this field current strengthens the magnetic field and allows the armature to generate a higher voltage. The higher voltage increases the field strength, and so on. This process continues until the output voltage reaches the rated output of the generator.