Voltage reading high!!! 17V - 18V

[ohe_boy]

OK, first of all a little history,

- Optima red top about 3 yrs old, Alternator - as long as I owned it from 2002.
- Driving to work one day, volt gauge started flucuating from mid to low.
- Put a volt meter across the battery terminals when it showed low, results showed (9V-10.5V)
- ASSUMED the alternator was bad, so bought a new one from Checkers.
- Replaced the alternator, started it up ran it for about 5mins. Everything test out SAT. With engine running, 14.5V across the battery terminals.
- Parked it over night.
- The next day, I went to start it and it didn't want to. Checked the voltage on the battery, it was 1.5V. :thumbdwn:
- Checked to see if I had left anything on. Int./Ext. lights, etc... none
- Charged up battery, didn't hold charge. replaced the battery with a new Red top.
- Connect it back up and now it's running at 17V-18V.

So I took the Alt. back to checkers to have it tested, they said it was GOOD. I don't believe them cause the only thing I can think of that could cause this high volts would be the alternator/voltage regulator.

What to do??? HELP??

 

[fixxxer]

How are you checking the voltage? DMM? VTVM? or the gauge on the dash?

 

[Tbars4]

...Since you have already had your Alt bench tested, I would take the battery out and bench test it also...(First thought is voltage regulator)

...I had a fuel relay that was going bad and it would start the fuel pump after the truck was turned off...You may have a similar parasidic drain that is taking your battery down and your alt was always charging it...Now your battery may be failing and the alt is just doing it's job...

..Another thought, what size alt are you running??? Have you checked your alternator wires as these may also be part of the problem...

 

[Dannyboy]

isn't the voltage regulator built into the alternator on our trucks?

 

[JDraper]

isn't the voltage regulator built into the alternator on our trucks?

Yep.

 

[Tbars4]

...Yes it is...If the wiring, or the battery is bad, it will keep trying to charge the battery...I'm not sure of what test they ran on the alt but some only check to see if they are simply charging..

...The voltage regulator can be bought seperately..
http://www.autozone.com/R,32522/veh...partType,00097/shopping/partProductDetail.htm

 

[BrooklynBay]

I think that it might be the battery terminals or the contacts might have corrosion on the ground terminal on the frame.

 

[ohe_boy]

So I found out the problem (so far) and lets see what happens tomorrow!!!

I seen the volt gauge on the dash cluster go up to 18V. Then I used a DMM on the battery to verify the 18V. DMM showed 17.8V so gauge was correct. So to answer the 2nd post...I used the gauge and a DMM.

My first thought was also the alternator so I took it down to checkers and they said it was good. I didn't believe them so I took it to Napa to get it tested and the guy there told me that it's no good. 6V was at the output and they have a primative machine. No computer, all analog!

Took it back to checkers (different day - different workers) and this time it failed the test. 3 times!!! SO they gave me another one, I had them test this one too. AND this one failed too. SO they gave me a third one. Finally this one past their test. SO to make sure, I took it to Napa and it also passed their test. SO i installed it and so far so good! 14.7V running!! Lets see tomorrow and see if the battery will hold the charge.

I guess when checkers do their alt tests, they don't think about the regulator or output voltage. I think that was the culprit.

Thanks for all the help guys!

 

[Tbars4]

...I am glad to hear you got it fixed...:biggthump

...I have made the same trek trying to have an alternator or battery tested...

 

[ohe_boy]

Thank tbars. Yah its hard to troubleshoot an electrical gremlin when someone tells you that somethings working when it's actually not!!! Damn, 3 days it took me and all it was, was a bad "new" alternator. Fricken Checkers!!!

 

[Kaidenh0]

"Voltage reading high"

Going through the exact same problem right now. Battery even smells from overcooking! I told Autozone I think the alternator is putting out too much voltage. They couldn't verify because when I went back, the car ran normal. So maybe the problem is a faulty connection somewhere? I know this post is 2 months old but it's the EXACT same thing I'm seeing on my '95 Exp.

 

[Tbars4]

...Pull your alternator and have it bench tested for free at one of the parts stores...The crash cart test they use won't isolate the problem...

 

[patrick112390]

either way- when you get close to 20v your computers brain starts frying and **** will only start at the pcm.....

 

[Kaidenh0]

Well, got it fixed guys. Turned out to be a bad "new" alternator. They ended up giving me another new battery as well because the high voltage was cooking the first new battery. I changed out both and did the serpentine belt at the same time.

The guy told me that low voltages can really mess with your computer. I had read on another thread that someone had their transmission replaced because of an O/D light.

That was our original problem about a month or two ago. We had the transmission replaced at AAMCO and truck ran fine except for when the O/D light came on. After fixing the alternator and battery, the light came back on and we've taken it back 4 times. They have been really cool in paying for a rental car and no charges for the repairs. Hopefully be getting it back tomorrow. Thanks for all the help on this board!

 

[BrooklynBay]

Thanks for the update!

 

[Tbars4]

...It's great that you got it fixed and they also replaced the battery...Most places won't take responsibility for the battery also...:biggthump

..Did you have the alternator bench tested or how did they figure it out???

 

[TedJ]

This seems to be a recurring trend I have seen in rebuilt alternators. They use cheap, cheap, cheap (Did I say cheap) garbage voltage regulators on them. I got one for my dad's Bronco, it worked for 20sec and died. (and this was from a local rebuilder, not even AZ or another cheapo parts store) Don't be afraid to blame your problems on the new alternator, its probably junk too. I ended up with another rebuild that had a Motorcraft regulator on it, which no suprise works fine.

And do be careful, voltages over 16v or so can really mess up the electronics on your truck.

 

[Kaidenh0]

...It's great that you got it fixed and they also replaced the battery...Most places won't take responsibility for the battery also...:biggthump

..Did you have the alternator bench tested or how did they figure it out???

They bench tested it. . It was cool that they replaced the battery. It tested fine afterwards but they still changed it. They replaced because I had just bought it from them with the bad "new" alternator.

This seems to be a recurring trend I have seen in rebuilt alternators. They use cheap, cheap, cheap (Did I say cheap) garbage voltage regulators on them. I got one for my dad's Bronco, it worked for 20sec and died. (and this was from a local rebuilder, not even AZ or another cheapo parts store) Don't be afraid to blame your problems on the new alternator, its probably junk too. I ended up with another rebuild that had a Motorcraft regulator on it, which no suprise works fine.

And do be careful, voltages over 16v or so can really mess up the electronics on your truck.

Yea! One of the guys from Autozone was telling me that high AND low voltages can do funky things to vehicles. Truck was having different issues that I have found on a different thread. Now that both problems are fixed...I hope to drive it another 100k miles. This site is great!

 

[Jason Parillo]

I know this is an old post, but my 95 ranger doing exactly the same thing.
Thanks for all the advice in advance and on my way to parts store .....