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Old 09-08-2008, 05:45 PM   #1
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fluctuating voltage

Something weird has started happening to my car. My voltage fluctuates between 14 and about 8 volts. I cant really narrow it down though. Ive checked all the connections to and from the battery for anything loose. I cleaned the battery posts and replaced the bolts for the pos. and neg. cables. Both the battery and the alternator tested ok at the local autozone.

The block to firewall ground strap is still the original and I was thinking ill replace that next. Are there any relays that could be bad thats causing this?

I want to fix this because when the cars at 14 volts it performs really well!, but as u can imagine at 10 volts it feels like a v6.

Oh and also it does not throw any codes.
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Old 09-08-2008, 05:47 PM   #2
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Re: fluctuating voltage

just wanted to ask did u check ur altinator? the car runs off altinator after being started for the most part
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Old 09-08-2008, 08:47 PM   #3
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Re: fluctuating voltage

Here is a thread => strikingly <= similar to yours. Note especially Post #1 where he describes the problem and Post #9 where he appears to have solved the problem.

He mentioned having his battery AND his alternator tested and they passed.

http://www.thirdgen.org/techboard/el...al-riddle.html
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Old 09-12-2008, 10:16 AM   #4
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Re: fluctuating voltage

Ok i had my alternator and battery tested and they pass ok.

What I have noticed though is that when the car is cool it will be running at 14 volts. Once the car warms up it dips to about 8-10 volts. Should I have had the alternator checked when the car was warm??? Can the performance of a alternator or battery degrade when the car warms up?
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Old 09-12-2008, 10:38 AM   #5
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Re: fluctuating voltage

CamaroRider that is a good link for troubleshooting this problem. I'm having a similar problem of a hot start issue whcih i've narrowed down to my starter.

Rv1890 the general answer to your last post is yes. Electrical components do decrease in performance when tempatures rise (also in cold weather they do). Wet cell batteries (non Optima style) have plates that can come loose and short the battery to the point of draining it. The cables and connections can come lose and cause intermitant(sp) problems. As noted in the other thread go thru ALL your connections and if the cables are questionable it's IMHO better to replace them.
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Old 09-12-2008, 02:18 PM   #6
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Re: fluctuating voltage

coolram62 is 'spot on' with his post.

I would look at your situation in the following ways:

1. The 'load' that your charging system and battery must support is NORMAL but your charging system and/or battery can no longer support it.

2. Your charging system and battery are working properly but your 'load' is abnormally high.

3. A combination of abnormally high load and improper working charging system and/or bad battery.

I think a proper battery test would charge the battery in a proper manner to full charge, let it 'rest' for XX minutes, discharge it at a somewhat high 'test load' for 'YY minutes', and plot the discharge curve. If that curve looks 'good' under those conditions I would be inclined to believe the battery is acceptable. However this test is not being performed stuck in traffic on a hot, humid day!

I would think an alternator might be harder to test properly except by a company that specializes in 'proper test methods'. In your case your alternator should be checked in an environment that duplicates your cold start, warm-up and hot engine => environments <=. I do not think this type of test is performed by the local auto parts outlet. So I will say that although your alternator has 'passed a test' that your alternator has probably NOT passed a 'proper' test for your situation. If it passed a 'proper' test then you could rule the alternator out as a source of the problem.

There is also a possibility that something within your car's system is drawing an abnormally high load while running which does not show up as low voltage at the battery/alternator until the car has 'spent enough time' warming up. In this case the engine being warm might not be related to the problem. I do not know what kind of a drain you should see on your battery/charging system during proper operation of your system. If you knew THAT then you could check for an abnormally high drain while the engine is running.

I would investigate the alternator again, but with more appropriate testing methods. I would find someone that specializes in testing that component. If the cost to properly test that component is the same or close to the cost of purchasing a new (or refurbished) alternator , I would purchase the new (or refurbished) alternator. With the new (or refurbished) alternator you could then eliminate that as a possible problem. Keep in mind that connecting a new, good component to a bad electrical circuit COULD ruin the new, good component. Sometimes you just have to take a chance.
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Old 09-12-2008, 02:18 PM
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