Voltage bouncing around?? | Ford Explorer Forums - Serious Explorations

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Voltage bouncing around??


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June 9, 2005
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Hi, I have a 91 and I just had my battery tested and it was all good, So I figured that maybe my alternator was going. I just had the alternator replaced and the voltage needle still bounces around when not on throttle.

The interior lights also flicker slightly. with my old alternator my bat voltage was reaching 16.8 volts, now its 15 at the very highest. So my old alternator was deffinatly messed.

Im just at a loss for what the needle would bounce and lights still flicker?

I hope i didnt just spend 200$ for nothing, but im putting a sub in soon so I figured better get a new alt regaudless.


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Do you have any subs or amps or aux lighting anything that is putting a draw on your charging system?

My k5's guage was bouncing around when the alternator's adjustment bolt got loose and slocked the belt, is your belt tight and in good shape?

ya, everything that I can think of relating is in optimal condition, is there a outside regulated source?,

My voltage gauge is doing the same thing, it bounces around at idle. The moment I put my foot on the gas, it steadies (completely stock 1991 XLT).

I've watched it for a while, and I noticed that it bounces in a very specific pattern... first there's a short bounce, then a long one, then a short one, etc. and it seems to match the feel of the engine's idle. This leads me to believe (on my Explorer anyway) that maybe the alternator or pulley has a slippery spot or a bad spot somewhere, I don't know. It just seems to match the engine's idle, but I could be wrong.

Edited to add, my lights don't flicker at all, though.

What amp alt are you guys using? Maybe you need the 130amp upgraded one.
Maybe bad/loose cables/connections?

i just got a stock 90 amp, so the regulator is internal?, 90 is easily sufficient

my 92 xlt auto kinda does the same thing. The volt gauge reads around the L on normal and starts flickering towards the max line at idle with nothing on and even does it with accessories on. I replaced the battery, alt, starter solenoid, battery cables, checked fuses, cleaned grounds and contact points and nothing stopped the volt gauge from going from high mid level to almost maxed out. A few things to solve this problem are to roll your rear windows up when the battery red lines itll drop it back down. If youre at a stop light just shift to neutral or park and rev the motor, itll never go past the red line and if it does it will guaranteed drop to normal if it comes close. This problem is normal for thes older explorers so nothing to worry about. Hope this helps!!

my 92 xlt auto kinda does the same thing

This problem is normal for thes older explorers
Symptoms you have described above and in other recent posts are not normal. The solutions you have offered should be at best considered once on the way to a location for servicing.

This is also a very old thread.

Symptoms you have described above and in other recent posts are not normal. The solutions you have offered should be at best considered once on the way to a location for servicing.

This is also a very old thread.
ChildIdenticacant: thank you for getting back at my post. Other than what i have described to remedy the situation nothing has helped remedy the cause of the volts shooting from mid level to high. Being under the hood and wiggling wires does nothing. It will happen when the motor is dead cold and warmed up, driving and idling. I keep seeing people talk about the big 3, what is that in detail if you could help. All the responses on this forum just tell me that Its not normal.

Thank you for any help. Joe

Life story before we get to the recipe:

I wanted to put a post together around the flickering voltage gauge at idle. It had been haunting me since I bought the truck 6 years ago. I tried alternators, cleaning and changing various grounds, replacing bulbs, verifying amperage and voltage interior and exterior, changing both positive and negative battery cables, and more. Finally, after building and replacing my engine EOY '23, I figured out what it was. When we removed the existing engine we removed part of the engine harness that lays atop the engine for the injectors, IAC, Temp, TPS, etc. It was the ONLY wiring we removed completely. This is the section that connects to the rest of the wiring harness next to the alternator. It is the large round connection above the smaller one sitting in its own bracket. When we reinstalled the new engine and connected everything back up I noticed the voltage gauge was rock steady. No more flickering. This lasted a few days before the flickering returned. After coming to the realization about the connector we removed above, I decided to open the connection and thoroughly spray it out with contact cleaner. It wasn't all that dirty but I did notice that the connector was not fully seated. If you've ever disconnected and reconnected this section of harness you'll note that it's tough to fit back together. When you think its seated, try a bit harder to push it together. In addition to this I took the harness that goes to the alternator out, cleaned all the contacts removing any old dielectric grease and wrapped the bare wires in 3m electrical tape. Lastly, I replaced the split loom and sealed the ends before reinstalling. When I pulled the truck in before this work the gauge was flickering as were the outside and inside lights, after the work on startup the gauge was rock steady and has been ever since.

  • Remove the large round connector next to the alternator. It is the larger of the two.
  • Clean both sides of the connector with a liberal amount of electrical cleaner. Blow both sides out before reconnecting.
  • When you think its connected try a bit harder to ensure the connection is seated.
  • Optional: remove the harness for the alternator and clean all connectors and wrap with electrical tap if you feel so inclined. The connector is behind the battery. It is a typical white, round connector with a 90 degree corner alignment.

Hello 96AWD, thank you for your help!! I greatly appreciate any info given on this subject but i have found the cause. Ill have to remember all that you have done incase the problem arises again. To recap everything, ( ill keep it short) no matter what weather condition or if the engine was operating temp or just starting from the day my problem would start right away or after idling for 15-20 minutes or just before i parked my volt gauge would go from a little above half to almost maxed out making my lights (interior & exterior) brighten and my blower motor if on would sound lounder. Some people would high beam me as my low beams would brighten then dim quite intermittently making me take the side roads home. I bought a bunch of stuff and nothing changed the condition. New alt, starter, battery cables, fender relay, a bunch of electrical cleaner, dielectric grease, chassis ground braids, new battery, fuses, tools ect and it would still persist. Well one day before all this cold hit lewis and clark county, i dove into my engine bay with my explorer running and fidgeting and almost wasting a pack of batteries on my multimeter checking voltage across EVERYTHING until i found something yielding consistent results. If i jiggled my positive battery cables id hear my blower (which was on high, you can hear it in the engine bay) go high and BINGO!! The new cables i got from autozone were faulty. I got the presoldered cables that matched my own and the thinner of the positive wires that led from the positive battery post cable to the left side of the fender relay was loose!!! So i clipped it from the lead terminal clamp and made sure it was making good contact and POOF! No more mid to high volts, now what i got is when i break and the rpms drop past 1000 the volts dip from mid to the N on normal. Ive heard this is normalish but im no longer worried im gonna fry my pcm. I am hoping someone can explain this in better detail whats happening for other peoples sake. Thank you 96AWD and everyone for the input!!!!