Ideal Alternator Output? (1 Viewer)

[CharlieS]

What should we expect to see for alternator voltage output on a healthy alternator?

If it matters, I have a 2013.

I've had a couple of variations of the HKB diode (fixed .6v increase and variable increase up to 1.0v), but all of a sudden I seem to be seeing lower charging voltage than I was previously. I dropped from a typical 14.6-14.7 v at 1500 rpm to 13.7-13.9 v at 1500 rpm with the diode in.

I removed the diode and went back to the stock fuse, to reduce the number of variables. I'm seeing mid to high 13v (13.6-13.9 v) in this configuration.

I want to catch any alternator or voltage regulator issues before they strand me in the BFE.

 

[RET2]

Doesn't your alt. temp. adjust?

 

[CharlieS]

It does, yes. Ambient around here has been in the low to mid 80's farenheit. Could that be enough to drive this change?

 

[RET2]

I've heard about .5 volt. Hopefully someone with intimate knowledge will correct me if I'm wrong.

 

[stonepa]

I'm confused - why change the stock config?

 

[tincan45]

You might have a bad diode. Those sound like stock voltages.

@stonepa - You need higher voltage to charge AGM properly. The diode is a quick hack to increase stock output voltage.

 

[CharlieS]

I'm confused - why change the stock config?

AGM battery in the starting position. Requires higher voltage to charge properly.

 

[RET2]

FWIW over on a Tacoma forum there are threads about a Ford replacement fuse/diode that does the boost. The great part is it costs about $12 from a Ford dealer.

 

[CharlieS]

Thanks, @RET2.

I have both the HKB fixed diode and the HKB variable diode. They both worked as designed for some period of time.

In the last few days I've noticed a significant drop in the output voltage (I have a digital gauge in the cabin to monitor both batteries).

I'm trying to figure out if my alternator is going bad, so I can preventatively replace it (or have it rebuilt).

Maybe a better question would be whether there is a way to test the health of my alternator?

 

[CharlieS]

You might have a bad diode. Those sound like stock voltages.

@stonepa - You need higher voltage to charge AGM properly. The diode is a quick hack to increase stock output voltage.

Is there a way to test the diode with my multimeter? There is a diode setting that I've never tried... Does this seem reasonable? How to Test Diodes

 

[grinchy]

Is there a way to test the diode with my multimeter? There is a diode setting that I've never tried... Does this seem reasonable? How to Test Diodes

Yep.

 

[prharper]

Yep.

I think we have similar setup. My 2018 w BCDC (without diode) averages about 13.6 main and 13.7 on aux while driving and 85 degrees out.

 

[RET2]

FWIW over on a Tacoma forum there are threads about a Ford replacement fuse/diode that does the boost. The great part is it costs about $12 from a Ford dealer.

Here it is guys 2005-2014 Ford OEM Diode 4F2Z-14A604-AA | OEM Ford Parts

 

[Markuson]

I'm confused - why change the stock config?

👁👁Just a detailto beClear...
The fuse hack doesn’t actually increase what the alternator is capable of producing. What is does instead is trick the system into thinking the battery voltage is lower than it really is...so that the alternator charge responds to the perceived low charge with a higher output. The net effect is you are getting consistently closer to what keeps AGMs happy. Still not perfect...so do tend your batteries regularly, but the hack gets you much closer to full charge than without.

I have the configurable HKBunit set to a full 1.0 with my AGMs. It has a series of switches that let you add resistance in 0.2 increments... so anywhere from 0.0 to 1.0.

You still need to battery tend your AGMs regularly.

 

[RET2]

Just for grins if you do any of these swap outs it would be prudent to carry the stock one as a backup. Not sure what would happen if the replacement grenades but I don't want to get stranded potentially.

 

[CharlieS]

Yes, good advice. I have spare fuses in the fuse box.

 

[CharlieS]

Well, I don't have a conclusive answer, but I think what I think is happening is that I am observing the temperature sensing alternator in action.

With higher temperatures, I think the temperature sensing alternator is doing what it is designed to do kicking the output down.

While the diode is still causing it to boost the voltage, it is still running ~.5 volts lower in warmer temps.

I have been looking for documentation about when the alternator reduces voltage, but so far have only found vague references, no specs. I'm guessing it is in the 75-85 degree Fahrenheit range. When the ambient temps drop lower I am getting the higher voltage again.

 

[gaijin]

Well, I don't have a conclusive answer, but I think what I think is happening is that I am observing the temperature sensing alternator in action.

With higher temperatures, I think the temperature sensing alternator is doing what it is designed to do kicking the output down.

While the diode is still causing it to boost the voltage, it is still running ~5 volts lower in warmer temps.

I have been looking for documentation about when the alternator reduces voltage, but so far have only found vague references, no specs. I'm guessing it is in the 75-85 degree Fahrenheit range. When the ambient temps drop lower I am getting the higher voltage again.

Sounds like you have a handle on it, but just for reference, here is what I see on my 2013LC with the fixed diode:

Before diode install:

After diode install:

HTH

 

[CharlieS]

@gaijin thanks.

 

[grinchy]

mine runs (on the teeny tiny dash gauge) over 14 reliably. I don't look at it too often. I'm not too sure ambient has much bearing on this, but maybe?