Do I need a new alternator?

[crushhour2086]

im not sure if this is the right area to ask this but I have a 2010 Dodge Ram 1500 with 4.7L engine. just last weekend I was driving with the AC on and I came to a light and when the aux fan kicked in, I saw the volt meter drop down halfway. Then it slowly recovered, so I went on a drive later and it did the same thing so I hooked up a mutimeter and watched it. It charges at 14.4 with lights and AC running but when the aux fan kicks in it drops to battery voltage and then recovers after a couple of seconds and I can tell the engine bogs down a bit until the alternator recovers but nothing serious.Never seen it do this before and I believe it should be able to handle that no problem without dipping like that. Battery is about 2-3 years old and after a week of sitting it was at 12.36v before I ran my test. Also no corrosion on any connectors or loose wires. Im pretty sure the alternator is going and wanted to ask your opinion.

 

[mb33458]

Hard to say. I would suspect your battery, but you will need to load test the battery to be certain.

 

[crushhour2086]

that's one tool I don't have, ill have to get one and try that first

 

[GTyankee]

any major auto parts store can load test your electrical loads
battery & alternator

 

[fireflymedic]

I'm wondering how much draw that fan is pulling. Could be the fan motor and not charging system.

 

[crushhour2086]

I'm wondering how much draw that fan is pulling. Could be the fan motor and not charging system.

I kind of suspected that too

 

[Socalramfan]

I was just thinking to myself, hmmm might be time to swap out to a new alternator myself after reading your post.

Im a big advocate on changing things out BEFORE they go as much as I can. I’d certainly recommend doing so even if it turns out to be the fan as well.

 

[BossHogg]

Electric motors have substantial current in-rush, depending on engine RPMs when the fan kicks in determines what the alternator can provide. For example, a healthy 160 amp alternator can provide 61 amps at 1500 RPMs but only 29 amps at 1200 RPMs. Depending on the current electrical load (the ignition system on a gas engine can consume between 4 to 8 amps of power) the battery's stored power will be called on to fill in what the alternator can not provide.

Sounds to me like your battery is getting weak and as suggested, you need to get it load tested. I would also have the alternator tested. Your issues could be with both on the threshold of performance.

If it were me, before I got into the extra labor of battery and alternator testing, I would take an exploratory look at the major battery/frame grounding points. Your observations can also suggest a failing grounding point. Don't just look at them, pull the bolt and clean the connection. Your truck's age and the climate you operate in make electrical connection points (very) suspicious.