Alternator needle gone crazy

[dking]

1992 Explorer 4Dr 4X2 4.0
I know I read some were about this but can't find the thread that I'm looking for. My alternator needle is jumping around when I'm at idle and driving down the road. Interior and exterior lights are flickering also. I've taken it to Auto Zone and Advance they checked it out and both told me the battery was bad. It was under warranty so they replaced it for free. The alternator was replaced about a year ago. Both places said it was ok. I remember some were that the battery cables could be bad and it could also be a grounding issue. I’m I right thinking this or could it be another problem? If it’s the cables where is the best place to get them? What gauge wire is the best?

 

[arco777]

Could be a failing voltage regulator, but I'd have a free charging system test done and see what comes up.

Cables can get corroded internally. You can test their resistance, but that may not give you the full story. Of course all connections need to be good too; a loose ground can screw stuff up just as well.

For cables, most auto parts stores will carry a factory replacement behind the counter - but you could also look online at sites like 1A Auto or RockAuto.

 

[Anime]

Sounds like the voltage regulator alright, but don't rule out the cables, since a bad cable or connection can prevent the alternator from having the strong electrical connection it needs to be charging the battery properly and providing the output.

Factory cables from the dealer are the best, but will run you ~$100 for both a positive starter and negative ground. Napa has some that are decent and cost quite a bit less if you don't require factory cables.

If the battery cables are pretty torn up or in bad shape, it might be worth your while to just replace them off the bat anyway. If they are in decent shape, you might want to just remove them to clean them up, clean the frame/block ground connections, check for any shorts or wear on the cable that could be causing a short, and stuff like that. Also check the ends of the cable itself, see if there is any blue corrosion in there. That doesn't always mean the entire cable is corroded, but a clean fresh cable with zero corrosion will do better than one that has minor corrosion, even if it's not enough to cause a big problem just yet.

If cables don't change it, it's probably the alternator itself. If it's a cheap alternator, "new" or remanufacturerd in China, it might not have the highest quality stuff. If it's less than a year old take it back where you got it, hopefully with a receipt, and get a new one under warranty. You could also possibly just get another voltage regulator, they are easy to replace, but the $20-30 it'd cost (although they are much less online) might not be worth it compared to just switching out the alternator for a new one, even if it's just the regulator.

 

[dking]

Thanks for all the input. I have not been on for awhile. My wife of 18 years passed away on 7/21/12 while on a family vacation at Kings Dominion. We had the youngest kids with us when it happened. It’s been a really tough month. I’ll be more active in the future. I just wanted everyone know that your advice did not fall on deaf ears.

 

[smegun]

just had similar experience had to jump 4 times to get home coming out of advance auto parts store battery will run car for awhile but as the battery gets drained I noticed on the second jump that my gages went haywire I had a full tank my rpm gage was 0 rpm and
my alt was all the way at 9 oclock then she just died in traffic without power stearing
emergency flashers or anything fuel pump has not turned on a couple times over past few days

im diagnosing it now I removed the aftermarket fog light wiring someone patched in near the inside fuse box it was spliced a few times also I noticed one of my tiny 15 amp fuses was blown in the engine compartment #17

Ill continue this DC grounding aftermarket effects may have surged everything cute the radiator hose is in the way of the voltage regulator to remove it ill have to collect prestone duh anyway I hope the system is tough

any one know how to load test or specifically test the vregulator it says test point but were is the link to test the drop or procedure I havnt got a 200 ammeter anywhere matts 94

 

[SwaintaN]

Had similar issues. Replaced the wiring set up in the explorer.. Went a little overkill on mine and fixed it all... I used 0gauge pretty much for everything but the starter was a 4 gauge. With Soldered/Crimped ends on everything as well for a better connection. I have a thread on here where i show and talk about it a little if you want me to post it.

 

[pattenpending]

have same problem with 92 explorer put in new alternator to day and still have problem I had battery checked at two places and it checks ok. Put on new positive battery connector no help. Looks like more investigation needed.

On this model the spark plug wires sometimes get on to hot manifold when this happens the entire care shuts down. Usually starts up again. Check for hot spots on all the plug wire especially the one close to the fire wall on passengers side.

 

[natenkiki2004]

The alternator hooks to the solenoid stud, not to the battery directly. It could be that your alternator to solenoid cable is toast?

Your spark plug wires shouldn't get hot like that, they're usually made of silicone and very heat resistant. Many are meant to be an inch or two away from blazing hot exhaust manifolds. You might have a short in one of the cables that gets worse with heat. If your cables are older, get em replaced. It's not much for a nice lifetime warranty set.

 

[larrydd999]

It's a cable, and not one of the heavy ones to or from the starter or you wouldn't be able to start the car - even with a jumper cable. Check the wiring associated with the alternator. The voltage regulator is inside the alternator.
Having said that, check the voltage at the battery with a digital multimeter. If it's stable you may be having a different problem such as a bad connection between the engine electrical system and your dash and interior system.