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IN car voltmeter goes up and down on start ups

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IN car voltmeter goes up and down on start ups

Postby Pissy » Thu Aug 20, 2009 1:26 pm

My in car battery voltmeter jumps up and down for a about 5-10 seconds on start ups when at idle. (doesn't do it when I rev it)
My dual battery monitor also show this jumping effect too, I have not done a multimeter reading but I would say it drops to 10ish Volts.
Just wondering if this could be down to my alt belt slipping or something else.
The jumps are like the same as when you indicate and there is a noticeable dime if you have the lights on and engine tone changes with each jump, (again only at idle, rev it goes away).

This has been going on for a long time now.
Any clues ?


Cheers
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Re: IN car voltmeter goes up and down on start ups

Postby geeves » Thu Aug 20, 2009 2:08 pm

what does the rev counter show? Im thinking that when cold its idleing slow and uneven and the low revs is causing low charge
Sanding your knuckles before starting work can help. That way you cant skin them
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Re: IN car voltmeter goes up and down on start ups

Postby pig75 » Thu Aug 20, 2009 2:15 pm

Check your earths
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Re: IN car voltmeter goes up and down on start ups

Postby Demonic » Thu Aug 20, 2009 3:42 pm

I notice the same thing in my Mu, its fine after you drive it for a bit, but on startup and maybe 2-4mins after that the in-dash batt gauge goes up and down.... only by 1-3v.
Cheers,
Andrew
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Re: IN car voltmeter goes up and down on start ups

Postby Pissy » Fri Aug 21, 2009 7:58 am

I doubt its earths as it only happens on start ups for 10 seconds.
I should have mentioned that its the start ups when I first use the car for that day (usually mornings to go to work and same again at the end of the day when I go home from work. It usually doesn't do it if the car has been on recently.
Could be something with the bushes needing a .......? warm up or something like that.
My car revs around 800 on idle.
The timing of the voltage drops are not random but a consist drop like a what happens when you use a blinker (the voltage drops with each lightflash and tick)

Sounds like Demonic has the same issue as me but mine only lasts for 10 or seconds, it goes away quicker if I rev it straight away on start up for 5 seconds?

I do have a piranha 150 amp dual battery isolator,...maybe its doing something,......but it does seem to be working fine give power to both batterys.

It not be an issue worth worrying but if its a sign of something failing then I need to sort it out now.

Cheers
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Re: IN car voltmeter goes up and down on start ups

Postby Demonic » Fri Aug 21, 2009 9:24 am

Pissy wrote:Sounds like Demonic has the same issue as me but mine only lasts for 10 or seconds, it goes away quicker if I rev it straight away on start up for 5 seconds?


2-4 mins was just an estimate, I only know it stoped doing it once i reach my destination but its usually stopped doing it in under a min. I just have the standard battery cables/links. It seem as the alt is not putting a constant flow of V's to the battery.
Cheers,
Andrew
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Re: IN car voltmeter goes up and down on start ups

Postby mulover » Tue Aug 25, 2009 10:21 am

I wouldn't worry about it, probably only because its still trying to charge the battery back up from start up, and the motor is not running smoothly yet, giving a rough charge.
Oh how i miss my mu, the lux is just not the same :(
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Re: IN car voltmeter goes up and down on start ups

Postby Pissy » Tue Aug 25, 2009 10:51 am

I hope so, I've gone through 3 alternators in 6 years, and the 120amp one is not cheap, around $500 plus and fitting.
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Re: IN car voltmeter goes up and down on start ups

Postby Aufgeblassen » Mon Sep 28, 2009 1:29 pm

Looks to be that the glow-plugs are cycling for a few seconds, my Ford E-350 RV does that for about 10 seconds too.
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Re: IN car voltmeter goes up and down on start ups

Postby Pissy » Wed Sep 30, 2009 1:59 pm

Well my alternator started playing up again, charging only 13.4 with spikes to 13.8.

Took it to auto electrician, he stripped and cleaned it and now he thinks its back to 14.2 normal.
He said the alternator was really dirty (I only went on the beach twice) and a slight bit of corrosion in/on/near the restrictor or resistor (I can't member which one).

At least its better than having to buy a new 120amp unit as the prices have shot up a fair bit apparently, well over $550.

I will ask him for the best my self service the alternator,...I'm guessing WD40 before and after big trips ?

Cheers
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Re: IN car voltmeter goes up and down on start ups

Postby geeves » Wed Sep 30, 2009 2:31 pm

unfortunately that will clog the brushes. Only thing that works is to stay away from sea water or muddy water.
You can try flushing with fresh water when you get home but this will only be partly successful. Otherwise its just a remove,strip and clean every 6 months or so.
My auto sparky told me to never go near sea water after spending 3 hours trying to get my starter out (so seized that it took a strong arm extension to turn the nuts the whole way down the thread) The following day at red rocks waves broke over the roof.
I dont think he likes me after that and the 1 month old alternator he had to rebuild after it completely filled with mud So much for warrentees
Sanding your knuckles before starting work can help. That way you cant skin them
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Re: IN car voltmeter goes up and down on start ups

Postby Pissy » Thu Oct 01, 2009 8:07 am

I'm going to find someone to put a bash plate under the engine to try and keep the alternator dry as much as possible when on the beach, it think it will help ALOT.
Only cost me $250 for a strip down and clean of the alternator plus a double check of the glow plugs circuit, better than the 800-1000 for a new one?

I feel so much better now ;)
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94 3.1L MU,2.5"suspension lift,2"body Lift,33"Bighorns,F&R Autolockers,Rock Sliders,winch bar,240 lightforces,UHF,120amp alternator,dual batteries,snorkel,turbo timer etc
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Re: IN car voltmeter goes up and down on start ups

Postby geeves » Thu Oct 01, 2009 11:52 am

thats expensive. Last time mine was done it was just an hour and a half labour which is 70 an hour. If you take it out yourself its even cheaper.
Sanding your knuckles before starting work can help. That way you cant skin them
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