voltage fluctuations only at idle

so I checked my voltages and need an opinion.

5.9 magnum. not sure which amp the alt is.
running the solid state 1 field voltage reg.
grounded the other field on the alternator.

battery voltage reads around 14.8 at idle.
Voltage reg sensing voltage reads around 14.5-14.7
The back of the alt jumps around 14.8 to 15.

Idle speed is about 800 rpm.

AT around 1k rpm the alt evens out and stops jumping around and sits at 14.5 with the same .2 drop from the battery to the vr.

Would you say it is the VR or just low rpm for the alt? no idea on the mileage on the alt. Jy replacement.

That sounds a bit high to me. But that little variation won't hurt anything.

not hurt, annyoing. It causes the lights to pulse at idle.

Alt. I'd pull/check/clean the brushes. Easy/quick to do

The voltage sense line you mention picks it's voltage from the battery, via the key switch. If that line is dirty then it'll sense lower voltage and up the alternator output.

Not sure how the electronic version of the older style regulator works, but the mechanical version is really just a switch turning the alternator on/off/on/off to maintain battery voltage. If the elctronic version does the same thing then it's operating normal. The mechinical style is adjustable as well, not sure if the electronic version is.

The newer style regulator (70 and up) varies the output of the alternator in a linear fashion, not the on/off/on/off method the old style uses. You can update to that style easily enough, NAPA sells the connectors for cheap.

What's the voltage at the headlights? Should be pretty bright with that kind of voltage.

Tom

they are bright. Didn't measure, but I have them tapped off a relay, so it should be close to that 14.8.

I will see if I can figure out how to take the alt apart with a spare one to clean the brushes.

Stumpy mentioned something I want to do, spraying the alt w something to clean it which sounds like it would clean the commutator bars/brushes as that is the make/brake connection point inside of it as long as you didn't wash the bearings/lube on each end

Quote:

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The voltage sense line you mention picks it's voltage from the battery, via the key switch. If that line is dirty then it'll sense lower voltage and up the alternator output.

Not sure how the electronic version of the older style regulator works, but the mechanical version is really just a switch turning the alternator on/off/on/off to maintain battery voltage. If the elctronic version does the same thing then it's operating normal. The mechinical style is adjustable as well, not sure if the electronic version is.

The newer style regulator (70 and up) varies the output of the alternator in a linear fashion, not the on/off/on/off method the old style uses. You can update to that style easily enough, NAPA sells the connectors for cheap.

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I don't think this is how it works. If it did, I would think I would get the same pulses higher up in rpm just like the instrument vr. but not sure.


I might try spraying it first, but will still take apart the spare to see what is involved.

Well spare is the wrong word, since it can't be used. accidently broke the main stud off of it.