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Voltage drop

Kingphil

Member
Joined
February 22, 2013
Messages
22
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City, State
Plainville,CT
Year, Model & Trim Level
94 explorer spt
I have a 94 explorer sport 4.0 auto 4x4 the problem I am
having is that under load alternator voltage drops from 14.13 volts
to 12.31. I am thinking that the alternator is going out
but would like second opinions before throwing parts at it

Thanks in advance
 



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~14 Volts is the alternator putting out power and charging the battery, ~12 Volts is just the battery sitting by itself, meaning the alternator isn't doing a thing.

It might be just the alternator brushes have worn down and so as they make intermittent contact, you sometimes get ~14 Volts, when they don't, you get ~12 Volts. It could also be that the voltage regulator is shot, and a new regulator might fix the problem.

You could try just replacing the brush assembly and/or the voltage regulator, but typically the contact surface on the armature is worn down as well.

If it's got 150,000+ miles, it wouldn't be a bad idea to spring for a "new" alternator, you can get China-made cheap-o's that work ok for $80-100. You can buy online from Rockauto, Amazon or even ebay, and get the same exact thing you'd get at a parts store or auto electrical shop for $100-200.


http://www.amazon.com/DB-Electrical-AFD0012-Alternator-Series/dp/B007Y87T1O/ref=pd_sim_sbs_auto_1

http://www.amazon.com/Discount-Star...placement/dp/B002UV4C74/ref=pd_sim_sbs_auto_3
 






You're battery might also not be up to par, many places will test the battery for free if you bring it to them.

You're battery could have lost it's power to run under load, batteries are very picky even running them dead a few times (once if it's completely dead, I.E. like <5V I think) can ruin they're CCA (cold cranking amps) to a state where it can't handle a load.

But at 150,000 miles anime is right you probably need an alternator anyways, but that might not be your only problem. It's also likely your weak alternator ruined your battery if it turns out to be a bad alternator.
 






The truck has 81,000 original miles I replaced the battery
about 3 months ago (due to age of old battery) battery load tests fine
I think Anime is right and the brushes are shot I may attempt to replace them
 






If it's only got 81,000 actual miles, the brushes won't be worn down unless it idled the equivalent of 150,000+ miles. The brushes in mine lasted 200,000+.

If the odometer only has 5 digits, that 81,000 could be 181,000 or 281,000.

If you want to attempt to change the brushes, you should probably get another voltage regulator as well, even if it's a cheap non-motorcraft one. I changed the brushes on mine, which then somehow managed to fry the voltage regulator.

Unless you can get the brushes + regulator cheap though, you might be better off spending the ~$75 on a whole new alternator vs. $20-30 on parts.
 






I might mention... this is a good opportunity to upgrade your alternator, if you have the smaller 90amp version (there are threads here with pictures to compare). It is a direct bolt/connector swap. I got a 130amp from a very popular online auction site fairly cheaply.
 






You can pretty much use any 3G alternator. Just have to swap over your pulley. I am using a 130amp out of a F150.
 






Thanks for the input guys went to the local autozone and picked up a 130 amp alt for 80 bucks
thanks to my reward card. Friday i get to replace the leaf spring shackles yay for me
 






I hope this isn't a stupid question. Is there a way to tell visually if the alt is 95 or 130 amps? I have been watching my volts gauge and it is headed south. I was wanting to know so when I went to the junkyard next time I could get one.

Before I get told junkyard parts aren't worth it, my budget allows that before new parts. And if it works for months or years that works for me.

I want to get the 130 amp unit (extra lights and stereo). I did search and best I could find was Limited models had the 130 amp alt. I was hoping there was a side by side shot comparison between the two.
 






The 130 amp should be bigger in size. Thicker then the 95 if you looking at them side by side. And as I said above you don't have to limit your search to just Explorers.
 






I hope this isn't a stupid question. Is there a way to tell visually if the alt is 95 or 130 amps? I have been watching my volts gauge and it is headed south. I was wanting to know so when I went to the junkyard next time I could get one.

Before I get told junkyard parts aren't worth it, my budget allows that before new parts. And if it works for months or years that works for me.

I want to get the 130 amp unit (extra lights and stereo). I did search and best I could find was Limited models had the 130 amp alt. I was hoping there was a side by side shot comparison between the two.

Here ya' go: http://alternatorparts.com/Ford_3G.htm
 












Thanks Phil.

I searched a good portion of yesterday on here looking for pics to no avail. I found the list of vehicles that used the higher amp alternators.

If you have an advance near you, you can print out coupons and its comes to under/around $80-100 new.just ask for a 97 explorer
 












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