Mystery Voltage Issue

[Evan L]

Hey all, made this account here to see if anyone could possibly help me out with this problem as I'm at a complete loss.

I have a stock 2000 Ford Explorer Sport with the 4.0 OHV V6

About 2 days ago when I dropped my stepdaughter off for school I noticed that when I put the truck in Park the battery meter dipped considerably low and the lights went dim. I shut it off as I had to go inside, but when I came back and restarted it the voltage was back to a considerably normal level. When I got back home I pulled out my multimeter to check what it was charging at and got a relatively steady 13.8.

I figured my alternator was going so I planned to pick one up on the weekend. It stayed at about 13.8 on my way to work that day and didn't move. 5 hours after I got to work and parked, I went to move the truck closer to the door. It fired up normal, and voltage was still around that 13.8. However, as I was sitting in the truck with it running, the voltage dipped considerably low again and all lights went dim. I shut it off, went back into work, changed and left to go home. Started it up and again it was at about 13.8 volts. On my drive home on the highway it held steady at 13.8 volts, but did dip pretty low once to about 12.5 and the battery light came on. However it only stayed like that for about 30 seconds before shooting back up to 13.8.

Once I hit the city the voltage would dip low to about 12.5 unless I held the brake at a stop light and revved the engine. Strangely enough, through the entire ordeal, not once did I notice any performance issues. My MPG dropped a bit but no other noticeable differences other than the lights dimming.

I grabbed another alternator from the wreckers the next day and put it in. Started the truck, and it was sitting happily at 14.8. I jumped in to take it for a test drive around the block, and by the time I got back the voltage had again dropped down lower than 13volts, and the battery meter would fluctuate upwards if I hit the gas. I swapped that alternator out with the old one again, fired it up, and it was charging at 14.5 volts. I let it sit running for about 5 minutes, and when I came back the battery meter on the dash was low, and my multimeter read about 12.5 volts.

So I've gone through and cleaned all my battery grounds. I had the battery load tested and it tested Good. I swapped out battery terminals, cleaned the posts on the battery really good, swapped out both alternators a couple times.

The thing that absolutely stumps me is no matter what alternator I have in there, when I start the truck it fires up fine and charges at a good 14.5 volts. But after it warms up a bit after about 5-10 minutes voltage immediately drops down below 12.5 and will not rise again. When I turn the truck off, resting battery voltage reads normal.

Anyone have any ideas?

 

[Mbrooks420]

Belt tensioner causing the belt to slip would be my first suspect.

 

[Evan L]

Belt tensioner causing the belt to slip would be my first suspect.

Would that explain why it only seems to be happening after the truck warms up?

 

[Mbrooks420]

Maybe. Other than a failing battery, or bad connection, it’d be at the top of my list.

 

[Fix4Dirt]

as rubber warms it expands

 

[Evan L]

Maybe. Other than a failing battery, or bad connection, it’d be at the top of my list.

I did have the battery load tested and it passed so I don't think it's that. I combed through about all my connections and can't seem to find anything wrong. I think I might pick up a tensioner and see if that helps things

 

[C420sailor]

If your belt has north of 80-100k on it, you’re well due for belt and tensioner.

 

[Fix4Dirt]

If your belt has north of 80-100k on it, you’re well due for belt and tensioner.

agreed. belt on this one has about 10k but tensioner is OE. havent come across an issue yet, but as is many cases, this one appears to bean outlier

 

[C420sailor]

The OE tensioners are really good

I’ve been using a Gates or whatever RA sells and I usually start getting light chatter approaching 100k

 

[Evan L]

If your belt has north of 80-100k on it, you’re well due for belt and tensioner.

I replaced the tensioner today and still the same problem. Belt still looks okay

 

[Evan L]

So as an update to my previous post, this is where I'm at now.

Stock 2000 Ford Explorer Sport, 4.0 OHV V6.

I was having trouble with my battery voltage staying steady at about 14.4 upon startup, but then after the truck warmed up it would drop drastically down to almost 12.4 and wouldn't go up.

Where I'm at now:
I cleaned all grounds, checked all fuses, had my battery load tested (it tested Good), swapped out my alternator for the one I got from the wreckers, replaced battery terminals and cleaned battery posts, replaced belt and tensioner.

The truck will charge, upon cold start, at a normal 14.4v. after warming up it drops a bit to around 13.8v and will stay there at idle. When I go to drive the voltage drops, but as soon as I give it any gas the voltage shoots up to normal. So when I drive it charges at about 13.8-14v. I swapped the voltage regulator from my old alternator as the plastic was ready to snap in half on the regulator that came on my junkyard alternator. But I swapped the brushes that were on the junkyard regulator onto the old regulator body, as the brushes from my original alternator were almost worn out. The junkyard brushes are about half worn

So, am I just unlucky and have two bad alternators?

 

[Lee's Automotive]

So as an update to my previous post, this is where I'm at now.

Stock 2000 Ford Explorer Sport, 4.0 OHV V6.

I was having trouble with my battery voltage staying steady at about 14.4 upon startup, but then after the truck warmed up it would drop drastically down to almost 12.4 and wouldn't go up.

Where I'm at now:
I cleaned all grounds, checked all fuses, had my battery load tested (it tested Good), swapped out my alternator for the one I got from the wreckers, replaced battery terminals and cleaned battery posts, replaced belt and tensioner.

The truck will charge, upon cold start, at a normal 14.4v. after warming up it drops a bit to around 13.8v and will stay there at idle. When I go to drive the voltage drops, but as soon as I give it any gas the voltage shoots up to normal. So when I drive it charges at about 13.8-14v. I swapped the voltage regulator from my old alternator as the plastic was ready to snap in half on the regulator that came on my junkyard alternator. But I swapped the brushes that were on the junkyard regulator onto the old regulator body, as the brushes from my original alternator were almost worn out. The junkyard brushes are about half worn

So, am I just unlucky and have two bad alternators?

seems normal my 99 explorer with the 4.0 SOHC charges at 13.6 when driving around and at idle and on cold start it's 14.5 14.6 and thats with a Remy 92520 alternator which is brand new and a brand new everstart 650CCA battery

 

[Turdle]

Threads merged. Best to keep it all in one thread

 

[Beargap]

So as an update to my previous post, this is where I'm at now.

Stock 2000 Ford Explorer Sport, 4.0 OHV V6.

I was having trouble with my battery voltage staying steady at about 14.4 upon startup, but then after the truck warmed up it would drop drastically down to almost 12.4 and wouldn't go up.

Where I'm at now:
I cleaned all grounds, checked all fuses, had my battery load tested (it tested Good), swapped out my alternator for the one I got from the wreckers, replaced battery terminals and cleaned battery posts, replaced belt and tensioner.

The truck will charge, upon cold start, at a normal 14.4v. after warming up it drops a bit to around 13.8v and will stay there at idle. When I go to drive the voltage drops, but as soon as I give it any gas the voltage shoots up to normal. So when I drive it charges at about 13.8-14v. I swapped the voltage regulator from my old alternator as the plastic was ready to snap in half on the regulator that came on my junkyard alternator. But I swapped the brushes that were on the junkyard regulator onto the old regulator body, as the brushes from my original alternator were almost worn out. The junkyard brushes are about half worn

So, am I just unlucky and have two bad alternators?

I had an issue in my '97 Explorer where the wire from the starter solenoid to the starter motor was rubbing on a heat shield and shorted out. You might check that.

 

[jlrohio]

So as an update to my previous post, this is where I'm at now.

Stock 2000 Ford Explorer Sport, 4.0 OHV V6.

I was having trouble with my battery voltage staying steady at about 14.4 upon startup, but then after the truck warmed up it would drop drastically down to almost 12.4 and wouldn't go up.

Where I'm at now:
I cleaned all grounds, checked all fuses, had my battery load tested (it tested Good), swapped out my alternator for the one I got from the wreckers, replaced battery terminals and cleaned battery posts, replaced belt and tensioner.

The truck will charge, upon cold start, at a normal 14.4v. after warming up it drops a bit to around 13.8v and will stay there at idle. When I go to drive the voltage drops, but as soon as I give it any gas the voltage shoots up to normal. So when I drive it charges at about 13.8-14v. I swapped the voltage regulator from my old alternator as the plastic was ready to snap in half on the regulator that came on my junkyard alternator. But I swapped the brushes that were on the junkyard regulator onto the old regulator body, as the brushes from my original alternator were almost worn out. The junkyard brushes are about half worn

So, am I just unlucky and have two bad alternators?

Did you ever determine what your issue was?

I'm having a similar issue, but different in a way. I'm searching through the threads tonight to see if anyones issues is similar to my suspected alternator issue (I may start a thread).

I'm just curious if you ever figured out what was causing the intermittent jump in voltage after you did all that you did - the easy stuff.

I'm holding out some small amount of hope that you will get notified of this reply and can come back and update your story.

 

[Evan L]

Did you ever determine what your issue was?

I'm having a similar issue, but different in a way. I'm searching through the threads tonight to see if anyones issues is similar to my suspected alternator issue (I may start a thread).

I'm just curious if you ever figured out what was causing the intermittent jump in voltage after you did all that you did - the easy stuff.

I'm holding out some small amount of hope that you will get notified of this reply and can come back and update your story.

Hey there!

I did actually end up solving it, and it was something that I managed to overlook completely somehow. The alternator I got from the wreckers was 90 Amps and my Explorer needed a 130 Amp one. I bought a new 130amp one months later and dropped it in, haven't had a single voltage issue since then.

 

[jlrohio]

Hey there!

I did actually end up solving it, and it was something that I managed to overlook completely somehow. The alternator I got from the wreckers was 90 Amps and my Explorer needed a 130 Amp one. I bought a new 130amp one months later and dropped it in, haven't had a single voltage issue since then.

Wow...after not seeing you signed on in over a year...figured you may not come back!

I'm reading through these alternator threads right now...and the amount of issues people have with the rebuilds in troubling to say the least - one guys thread I just read...went through three brand new alternators before finally getting a good one.

Where did you end up getting your 130 Amp one from?? Hopefully you continue to stay lucky!

My issue (which I'll probably start another thread about), involved intermittent jumping voltage upon startup and pulsing of the dash light, the headlights, needle well below 1/2 on the voltmeter thing on the dash. When I put my volt meter on the battery to test for voltage from the alternator, it was in the 15+ range and slowing going higher, 16, 17, etc...at that point, I had my kid turn the vehicle off.

After checking all connections real quick, the battery was still in the 12.5 range so I had him start it again and the battery was staying in the normal 14.3 range at the battery terminals and the lights stopped pulsating.

Every time we go out to start the car, the flickering/pulsing is happens for about 2-3 mins. By the time I get the voltmeter out there - everything goes back to normal (14.3 volts from the alternator). Anyway, I took apart everything like you did today and removed all instances of any corrosion and got everything down to shiny metal for grounding purposes. I also took out the alternator, sanded all three connection spots where the bolts attach to the engine, took off the top of the alternator and removed the voltage regulator to inspect it - there is some issues with the lower spring loaded arms but didn't really see anything crazy - I took some pics...so I'll probably start my own thread (even though it looks like I've started one here - LOL).

As I said, your issue sounded similar - but opposite. I'd like to keep my original stock alternator (again, based upon the horror stories I've read here on the remanufactured ones) if I can and just replace the voltage regulator ( Motorcraft - F77U-10316-AA) if I can find a real one.

 

[Evan L]

Wow...after not seeing you signed on in over a year...figured you may not come back!

I'm reading through these alternator threads right now...and the amount of issues people have with the rebuilds in troubling to say the least - one guys thread I just read...went through three brand new alternators before finally getting a good one.

Where did you end up getting your 130 Amp one from?? Hopefully you continue to stay lucky!

My issue (which I'll probably start another thread about), involved intermittent jumping voltage upon startup and pulsing of the dash light, the headlights, needle well below 1/2 on the voltmeter thing on the dash. When I put my volt meter on the battery to test for voltage from the alternator, it was in the 15+ range and slowing going higher, 16, 17, etc...at that point, I had my kid turn the vehicle off.

After checking all connections real quick, the battery was still in the 12.5 range so I had him start it again and the battery was staying in the normal 14.3 range at the battery terminals and the lights stopped pulsating.

Every time we go out to start the car, the flickering/pulsing is happens for about 2-3 mins. By the time I get the voltmeter out there - everything goes back to normal (14.3 volts from the alternator). Anyway, I took apart everything like you did today and removed all instances of any corrosion and got everything down to shiny metal for grounding purposes. I also took out the alternator, sanded all three connection spots where the bolts attach to the engine, took off the top of the alternator and removed the voltage regulator to inspect it - there is some issues with the lower spring loaded arms but didn't really see anything crazy - I took some pics...so I'll probably start my own thread (even though it looks like I've started one here - LOL).

As I said, your issue sounded similar - but opposite. I'd like to keep my original stock alternator (again, based upon the horror stories I've read here on the remanufactured ones) if I can and just replace the voltage regulator ( Motorcraft - F77U-10316-AA) if I can find a real one.

I got my alternator off of Rockauto, it's a Pure Energy brand cost me around $135 CAD. I know exactly what you mean when you describe your voltage fluctuating and pinging the dash light, that's what my original alternator would do. I took the regulator off and the brushes were worn down to almost nothing. With the way yours is overcharging too it definitely sounds like that voltage regulator may not be so good.

I found that NAPA sells the regulators themselves but they come without brushes (at least in Canada I was told), I believe Wilson makes them. I hope you can find out what the issue is soon!