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Alternator overcharging - 4JG2

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Alternator overcharging - 4JG2

Postby TimboTheKiwi » Mon Jul 11, 2022 9:57 am

I have a bit of an issue with my Wizard 4jg2 where it overcharges at times. When you start up and idle it will sit at about 14v but when you get out on the road and put a load up it it can peak it 16v + for short moments of high RPM. Things I have tried thus far...

- Looked at and changed charge relay - no change.
- Looked at all fuses under the bonnet and under the dash - no blown.
- Visually looked at groundings around the battery and alternator
- Removed alternator replacing the voltage regulator, bearings and seal - I thought this would have fixed the problem but I installed and still the issue is there.

When I made the repairs and put the alternator back in it now has an intermittent no-charge on start up and the battery lights etc will illuminate on the dash - this doesn't happen all the time and seems to come back online after a wee rev and will stay this way which is weird - has anyone put these alternators back together and had a similar thing? I suspect it is the new bushes not sitting quite perfect but I could be wrong there - I believe this is an unrelated issue to my main concern.

I haven't been driving it to work but the car I have needs to be returned so to get myself to work without any issues I will be turning on virtually everything the truck has to soak up as much voltage, which seems to be doing the trick to prevent further damage to other components but would love to get it back to normal as this is just temporary.

Any ideas would be greatly appreciated - it's got me scratching my head!
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Re: Alternator overcharging - 4JG2

Postby pig75 » Thu Jul 21, 2022 12:48 pm

One of my mu's does this never been a problem. If it gets to high turn the lights on
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Re: Alternator overcharging - 4JG2

Postby TimboTheKiwi » Thu Jul 21, 2022 1:43 pm

Thats good to know it it shouldn't cause much grief and yes I have had everything I can running so I am hoping doesn't get worse and start blowing things up...I guess the first thing to go would be the battery and other things like ABS etc.

Thanks pig!
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Re: Alternator overcharging - 4JG2

Postby IanC1965 » Fri Jul 29, 2022 9:54 am

Hi Timbo, I had the same problem with my old Rodeo, I kept the lights on all the time, turned out to be a diode in the alternator.
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Re: Alternator overcharging - 4JG2

Postby TimboTheKiwi » Mon Aug 01, 2022 3:19 pm

Thanks Ian - very helpful.

Soo, I just left it at that and thought I could get away with driving around with some extra lights on etc...but yesterday the high voltage cooked my battery...lol...to be fair it was 5 years old so it was on it's way out anyway but this must have pushed it overboard.

I have been looking at what rectifiers/diodes are worth and geez they are steep...most auto stores have them for about $250NZ but found one at www.as-parts.nz for $160.
After I find one to put in, I need to find a large enough solder iron that can heat up to join to the windings....ahhh fun!
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Re: Alternator overcharging - 4JG2

Postby geeves » Mon Aug 01, 2022 5:03 pm

If you have enough knowledge you can test your diodes and take the faulty one to Jaycar to match it. Should make it even cheaper. The price you had above was probably a complete diode pack
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Re: Alternator overcharging - 4JG2

Postby stardog » Mon Aug 01, 2022 10:01 pm

This is the one i installed on one of alternators i got a turbo solderer from j car as well to do the soldering.
https://www.ebay.com/itm/324792386198
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Re: Alternator overcharging - 4JG2

Postby TimboTheKiwi » Wed Aug 10, 2022 10:04 am

geeves wrote:If you have enough knowledge you can test your diodes and take the faulty one to Jaycar to match it. Should make it even cheaper. The price you had above was probably a complete diode pack


Thanks Geeves - my knowledge of almost anything electrical is limited at best - the guy at Butlers who had some experience with rebuilding alternators looked over the diodes and said they were all good, but I guess internally tells a different story

stardog wrote:This is the one i installed on one of alternators i got a turbo solderer from j car as well to do the soldering.
https://www.ebay.com/itm/324792386198


Thanks stardog - Damn thats a good price - if I could wait for a month or so for delivery that would be a great option.

I ended up getting the $160 one so hopefully (it is literally the only remaining thing in the alternator that hasn't been replaced, bar the slip ring) this does the job and I can drive the thing without any worries.

Update: I ended up taking the battery to get load tested and it came back all good which is weird. The initial problem was overcharging, but I am guessing the diode failed completely that day and would no longer charge the bat, which is why I presumed it was a dead batty (it went down to 3v). So, hopefully it is just the diode and it hasn't damaged anything else ie the voltage regulator. Probably did some damage to the battery getting down that low in voltage also.
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Re: Alternator overcharging - 4JG2

Postby stardog » Wed Aug 10, 2022 9:42 pm

This is the one i installed in my 120amp alternator as well at the moment im running a 80amp alternator in the wizard.
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Re: Alternator overcharging - 4JG2

Postby TimboTheKiwi » Mon Aug 15, 2022 12:57 pm

Sooo some success... after attempting to solder the rectifier to the windings and having no luck with doing so (I purchased what I thought would be a grunty enough 100w solder iron - but still not hot enough to attach to those big ears). I took it to Tower Auto in Christchurch for them to put it in properly - glad I did as now I know it was done correctly.
When I was installing the damn thing into the vehicle for the 3rd time I was still 50/50 on whether this time round would work...but I started it up and it went right to 14'ish Volts and stayed there. Even when I rev it up or down, load or no load it just stays dead on that same voltage which is very cool.

So problem solved - thanks to all who helped out along the way! I appreciate it.
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