Alternator output voltage

[getdealtwith]

Howdy folks. My '04 Navigator's 8 month old 650cca Superstart battery tests good and takes a bench charge well but drains too quickly to no-start with the "ignition on" / engine off. (Fan on, audio on, doors closed, lights off). Less than 10 minutes and I need a jump.

My alternator puts out 13.75 - 13.8V at idle which is low compared to the 14.3V I'm seeing in my 04 Expedition. No drain issue there. The alternator was replaced by an Indie for the PO 30K miles ago. I tested for voltage drops: OK. Connections are good.

I'm finding conflicting information about the acceptable range. Some are saying it should be at least 14V and up to 14.7V to properly charge lead acid batteries, others 13.5V to 14.2V.

Before I modify the alternator with a diode in the ground connection or buy a replacement, can others here comment on their output voltages?

Also, what is your experience with aftermarket replacement brands? Recommendations?

Thanks

 

[Hamfisted]

That's a pretty quick draw down ! If you take the cover off your fusebox and run your hand over the fuses and relays do you feel one that's hot to the touch ? If ones hot what circuit is it powering? If you do an amp test at the battery, how many milliamps (or amps in your case...) is it pulling with everything off? If you do end up replacing the alternator again, I would stick with NAPA. 110 AMP unless your Navigator has FACTORY navigation option.

 

[Yupster Dog]

I'm finding conflicting information about the acceptable range. Some are saying it should be at least 14V and up to 14.7V to properly charge lead acid batteries, others 13.5V to 14.2V.

It should defiantly be above 14v I would check your connections for corrosion first thing to go with a weak connection is the charge for the battery. A VOLTAGE DROP TEST will find any weak spots and help you keep your full charging capacity.

If that all looks good take to Auto Zone let them test alternator while on the truck, they test alternator, voltage reg and the diodes.

If you do find out you need another alternator @Hamfisted post is the way to go.

 

[getdealtwith]

@Hamfisted IKR!? - Thanks.

Sooo the only relay that gets a little warm (not hot) is 201, trailer tow park lamp...

With all lights on, radio, fm transmitter plugged in (cigarette lighters draw quite a bit) etc. I'm seeing 13.55V at the battery. Not great.

It does have factory Navi. Not sure what alternator they replaced the original one with but are you saying the vehicles equipped w Navi came stock with >110A alternators or are the aftermarket ones at with that output just weak sauce and it makes sense to step up in output?

I'm fine buying a 135A or 200A unit from a solid brand. Got a link to one you'd recommend at Napa?

 

[getdealtwith]

I need to add that after 30+ minutes of testing with the engine running, the battery is showing 12.86V which means it's slightly overcharged, so charging is happening despite the low-ish voltage.

How do I best test for parasitic draw / a bad ground in the tow lamp circuits?

Also: just because batteries have become so hit or miss, I might have to take mine to O'Reilly to load test it. If I replace it, it'd probably be a 850cca group 65 one.

Thanks!

 

[Hamfisted]

Yes if your Nav came with factory navigation you would need the 135 amp alternator. NAPA is the best you're gonna find other than a new one from the dealer, and they're a local retailer you can go back to if you have problems or need warranty service. Just curious, has there been any aftermarket electrical items added to the truck ? Has anybody done any trailer plug work at the rear of the truck ? That 201 relay really shouldn't be warm unless you have a trailer plugged in with the lights on. Or compare it to the same relay in your Expedition to be sure. When you do your amp draw test pull that relay out and see if the amp draw drops.


Here's a good video explaining the process of doing parasitic draw tests on your vehicle How to Do a Parasitic Draw Test on Your Vehicle








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[getdealtwith]

I bet the PO replaced the alternator with a 110A unit but we'll know soon.

The only custom item on this truck is they had a car audio shop install an aftermarket DVD player that broke. I ripped that out and replaced it with a new player (w/o DISC drive) but there's no draw with the ignition off on that circuit.

I'll watch the video, get the battery load tested and pull the relay. It seemed odd to me, too that it got warm since nothing is hooked up. If the battery load tests OK, I'll turn the ignition on and see how long it takes w/o this relay before I get the low voltage beep.

Thx!

 

[GAINMOB]

once u get it figured out...go agm battery instead of acid

 

[mbtech2003]

I upgraded my 05 expo’s 110 amp to 135 from rockauto. 150 for a brand new one. 1-1/2 later still kicking. Any Napa one I’ve used have died every year. Might just be my bad luck. But I won’t buy another reman starter or alternator again. With all loads on at idle 13.5 volts is acceptable. Low. But still charging. Battery should not die in 10 minutes. Get a Interstate mtp- hd battery. Worth it. And will last 7+ years.

 

[getdealtwith]

I ordered a new 135A alternator from Rockauto. Didn't see a 135A option at Napa. I tested for parasitic draw an hour after locking the truck and got 20mA, so within the acceptable range. Will look into a bigger battery.

Thanks everyone for the input so far.