1977 New Alternator overcharging

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Jul 23, 2016 | 08:09 PM

xkeots

Thread Starter

Burning Brakes

Joined: Apr 2009

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1977 New Alternator overcharging

I just got a Delco reman alternator for my 1977 L-82. I just checked the voltage at battery as batt gauge on dash was high. At battery it is getting 15.10 V. That is a bit high. Any thoughts here?
Thanks
Jax
1977 Vette

Last edited by xkeots; Jul 23, 2016 at 08:09 PM.

Jul 23, 2016 | 08:34 PM

mikem350

Melting Slicks

Joined: Feb 2006

Posts: 3,105

Likes: 96

From: Sunrise FL

Quote:

Originally Posted by xkeots

Compare the voltage at the alt output stud and then across the battery. Should be about the same.

Then check ALL the grounds from the battery and from chassis to frame. Then check wiring to/from the alternator. If this checks out then the regulator is bad (located inside the alternator)...means replace.

Jul 24, 2016 | 10:20 AM

xkeots

Thread Starter

Burning Brakes

Joined: Apr 2009

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Just ordered another alternator under warantee. This one is putting out over 15v at idle. Battery ends burning hot, batt terminal on alt hot. Same rating on alt. over 15v

Jul 24, 2016 | 12:55 PM

mikem350

Melting Slicks

Joined: Feb 2006

Posts: 3,105

Likes: 96

From: Sunrise FL

Quote:

Originally Posted by xkeots

Just ordered another alternator under warantee. This one is putting out over 15v at idle. Battery ends burning hot, batt terminal on alt hot. Same rating on alt. over 15v

What was the reason for changing it in the first place? Was this a new problem? How long have you owned the car?
It MAY be possible that the battery is bad. What is its voltage not running?

Re-read my #2 response about checking the wiring first.

Last edited by mikem350; Jul 24, 2016 at 12:57 PM.

Jul 24, 2016 | 01:31 PM

SIXFOOTER

Le Mans Master

Joined: Jan 2006

Posts: 9,192

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From: Boca Raton Florida

The new alt may be bad as you suspected, did you get it tested? This is a 3 wire alternator correct? Check the 2 small wires on the side, make sure they are intact and have the correct voltage on them.
Checking the basics is always good: Battery and alternator grounds, charge wire going to the battery etc..

Jul 24, 2016 | 03:41 PM

lionelhutz

Race Director

Joined: Apr 2007

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From: South Western Ontario

Check that the heavier red wire has battery voltage and that the terminal is good and connecting to the alternator tab.

Jul 24, 2016 | 05:09 PM

Joebrick

Instructor

Joined: Jun 2008

Posts: 233

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From: Marietta Ga

I had a similar issue and it was the plastic connector (two-wire) plugged into the alternator. It wasn't a tight connection and pulled a high voltage constantly. Bought a new connector at Napa, soldered the wire connections, covered with heat shrink tube and all is well.

Jul 24, 2016 | 07:15 PM

xkeots

Thread Starter

Burning Brakes

Joined: Apr 2009

Posts: 828

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I changed the original alternator that was putting out perfect voltage, because the inner bearings were very noisy.
Jax

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Aug 13, 2016 | 06:18 PM

Doug1

Safety Car

Joined: Sep 2012

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From: Palm Harbor, Florida

Can an overcharging alternator blow the fuse for the gauges? The fuse that is also part of the GEN light and many other functions on the dash.
Thanks

Aug 14, 2016 | 12:02 PM

#10

xkeots

Thread Starter

Burning Brakes

Joined: Apr 2009

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Quote:

Originally Posted by Doug1

Can an overcharging alternator blow the fuse for the gauges? The fuse that is also part of the GEN light and many other functions on the dash.
Thanks

It depends on how high and how long it is running. Fuses are made for too much power in line to pop. Go online and see a guide for different rated fuses and how much voltage each will max out at. If there is a short or you are pushing 17v there is a chance fuses will pop if circuit was turned on

Jax

Aug 14, 2016 | 06:18 PM

#11

Doug1

Safety Car

Joined: Sep 2012

Posts: 4,688

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From: Palm Harbor, Florida

Quote:

Originally Posted by xkeots

Thanks for the response, didn't want to hijack the thread. Here's the deal, when I drive my car, kinda like an old man, I can use it as a daily driver for weeks with no issue. I also have an '02, but my driveway is only so big, so I always keep one car with my brother, so he will use it. So the last two times that he has had the 78, he blows the fuse, as in within hours of getting it, while I can drive it for weeks with no problems. He drives like a nut, The alternator is kinda new, Autozone foreign made thing. I've noticed the voltmeter a little higher than my previous alternator, that's why I'm suspicious of the alternator, those factors.
Thanks again for responding, my bro is too lazy to change the fuse, so both cars are at my house right now, I get tired of hearing from him within a few hours of him having the car. The windows won't go back up after he burns that fuse and it has been raining almost everyday lately.

Last edited by Doug1; Aug 14, 2016 at 06:19 PM.

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