Tachometer fluctuations due to bad alternator - Team Camaro Tech
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post #1 of 20 (permalink) Old Oct 12th, 17, 08:34 AM Thread Starter
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Robin
 
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Tachometer fluctuations due to bad alternator

I am posting this and hopefully making it easily searchable to try and help others who may have the same problem. I was having problems starting my 69 and problems with dim lights. My battery could not be fully charged using a charger and I replaced it. At the same time, my tachometer had begun to fluctuate wildly. I figured I would deal with the tachometer later. After replacing the battery, I thought it would be a good idea to check the alternator which had an internal voltage regulator. It was not charging. It also tested bad at Autozone. I replaced the alternator and my tachometer began to function normally again. Glad I found this when I did because I was about to take the tachometer out to inspect and possibly replace it. I could also see my console gauges much better at night. The battery had less than 3,000 miles on it and the alternator probably had half of that. Hope this helps someone when trying to diagnose tachometer problems. All was even better when Autozone replaced the battery and alternator at no charge. (No pun intended)
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post #2 of 20 (permalink) Old Oct 12th, 17, 10:30 AM
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Re: Tachometer fluctuations due to bad alternator

Make sure the alternator is well grounded to the engine and its brackets, and that the engine IS the buss bar for the rest of the car to ground to. This means the battery negative cable needs to go to the engine, then out to the other areas to ground, NOT be an ancillary point of ground.

Rarely, those fluctuations can be caused by a diode inside the alternator going bad, rarely.

Internal regulators can, and do go bad, mostly from bad grounding of the alternator. Same goes for either point type, or Wells VR715 electronic type regulators for remote regulator alternators.

Good catch and fix on your charging, tach and lights problems.
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post #3 of 20 (permalink) Old Oct 12th, 17, 02:35 PM
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Re: Tachometer fluctuations due to bad alternator

Not to hijack anything here, but a grounding question.

Is there any problem grounding the battery to an aluminum head?

I know aluminum was used for basic home wiring for a time, in fact the service wire at my home right now as I type is aluminum and I do realize aluminum will not carry the same amperage compared to a equal size copper wire ... but it is none the less a decent conductor of current.

I ask because I have folks regularly point out that my battery is grounded to an aluminum head.

I also have a battery ground to the inner fender, plus another from the rear of that same aluminum head to the firewall.

I do not seem to have any problems on account of bad grounds from the battery.

Again, my question is regarding grounding to aluminum heads ...

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post #4 of 20 (permalink) Old Oct 12th, 17, 05:06 PM
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Re: Tachometer fluctuations due to bad alternator

Move cable to block as alum does not conduct current very well.

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post #5 of 20 (permalink) Old Oct 12th, 17, 05:23 PM
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Re: Tachometer fluctuations due to bad alternator

Quote:
Originally Posted by Everett#2390 View Post
Move cable to block as alum does not conduct current very well.
Aluminum is just below Pure Gold and Steel is ranked 11th

Material IACS (International Annealed Copper Standard)

Ranking Metal % Conductivity*
1 Silver (Pure)105%
2 Copper 100%
3 Gold (Pure) 70%
4 Aluminum 61%
5 Brass 28%
6 Zinc 27%
7 Nickel 22%
8 Iron (Pure) 17%
9 Tin 15%
10 Phosphor Bronze 15%
11 Steel (Stainless included) 3-15%
12 Lead (Pure) 7%
13 Nickel Aluminum Bronze 7%
* Conductivity ratings are expressed as a relative measurement to copper. A 100% rating does not indicate no resistance.
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post #6 of 20 (permalink) Old Oct 12th, 17, 05:27 PM
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Larry
 
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Re: Tachometer fluctuations due to bad alternator

Quote:
Originally Posted by Everett#2390 View Post
Move cable to block as alum does not conduct current very well.
OK, That 's what car people keep saying.

What I see though researching, plus what I have learned over the years indicates that aluminum is a better conductor of electricity than is iron.

Is there something here (some other factor) I am missing?

According to this chart only Gold, Silver and Copper are better conductors.

https://www.thebalance.com/electrica...metals-2340117

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post #7 of 20 (permalink) Old Oct 12th, 17, 05:29 PM
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Re: Tachometer fluctuations due to bad alternator

LS Engines are all Aluminum

Just sayin

Head or block will both work
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post #8 of 20 (permalink) Old Oct 12th, 17, 07:19 PM
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Rufas
 
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Re: Tachometer fluctuations due to bad alternator

So are motorcycle engines, aluminum, no problem in using aluminum as a grounding point/buss. ONLY condition that adversely does connects in, is corrosion/rust, dirt, grime, loose connects, etc. Keep it clean and tight, should be OK.
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post #9 of 20 (permalink) Old Oct 12th, 17, 08:00 PM
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Re: Tachometer fluctuations due to bad alternator

High tension power lines are made of aluminum. If it wasn't a great conductor, they wouldn't use it and on top of that, it's relatively cheap.

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post #10 of 20 (permalink) Old Oct 12th, 17, 10:27 PM
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Re: Tachometer fluctuations due to bad alternator

Here's my input.

If I had a choice between connections I would choose a good connection to an aluminum head over a poor connection to an iron block. I would then if needed in a different situation choose a good connection to an iron block over a poor connection to an aluminum head.

Basically to me, a good solid connection is the important point.

I have not been exposed to different setups with let's say aluminum heads, but there are issues that can occur due to dissimilar metals. I'm not up to speed with all of that stuff but I have seen connections issues I cannot explain even though the connections were clean and tight from the start but then later, the connections go south. It could very well be due to dissimilar metals.

As far as aluminum being used as a conductor, it is being used in a lot of applications but the real importance to me is the ampacity of a conductor.

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post #11 of 20 (permalink) Old Oct 13th, 17, 08:30 AM Thread Starter
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Re: Tachometer fluctuations due to bad alternator

Quote:
Originally Posted by dave ray View Post
Make sure the alternator is well grounded to the engine and its brackets, and that the engine IS the buss bar for the rest of the car to ground to. This means the battery negative cable needs to go to the engine, then out to the other areas to ground, NOT be an ancillary point of ground.

Rarely, those fluctuations can be caused by a diode inside the alternator going bad, rarely.

Internal regulators can, and do go bad, mostly from bad grounding of the alternator. Same goes for either point type, or Wells VR715 electronic type regulators for remote regulator alternators.

Good catch and fix on your charging, tach and lights problems.
Dave Ray, My negative cable is grounded to the engine, but I am not sure that I completely understand the rest of the last sentence of your first paragraph. Even at it's best, I have always had a problem with dim interior lights and gauges. They are better now, as I said in my first post, but not what they should be. Somebody driving behind me one time even said that my taillights were dim. He was a car guy and said that he thought I had a ground problem. I have tried to clean every ground wire that I could find. Do you think what you are saying could have some relevance to the dim lights?

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post #12 of 20 (permalink) Old Oct 13th, 17, 09:45 AM
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Re: Tachometer fluctuations due to bad alternator

The engine block also needs to be grounded to the body since all the lights are using the body as ground. If you have rubber engine mounts, you may not be getting a good enough ground. Same goes for the radiator support which also needs to be grounded to the body.
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post #13 of 20 (permalink) Old Oct 13th, 17, 07:39 PM
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Rufas
 
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Re: Tachometer fluctuations due to bad alternator

As blitzer says, good ground from engine to chassis and body are essential.

Now, think about this, everyone, stock battery ground on the engine is by either a STEEL bracket, usually for the alternator, OR, a STEEL double threaded bolt of some sort, such as for an intake manifold. So, one could say the engine end of the ground goes to STEEL, not aluminum, or cast iron.

Yes, bad/compromised grounds will make for lower head light outputs. Also, the wiring connectors at the bulk head connector on the dash can get corroded badly, which would make for low lighting output. Start cleaning/tightening, there's lotsa places to look into.
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post #14 of 20 (permalink) Old Oct 16th, 17, 07:45 AM Thread Starter
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Robin
 
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Re: Tachometer fluctuations due to bad alternator

Quote:
Originally Posted by blitzer454 View Post
The engine block also needs to be grounded to the body since all the lights are using the body as ground. If you have rubber engine mounts, you may not be getting a good enough ground. Same goes for the radiator support which also needs to be grounded to the body.
Thanks, I'll check it out.

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post #15 of 20 (permalink) Old Oct 18th, 17, 07:49 PM Thread Starter
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Robin
 
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Re: Tachometer fluctuations due to bad alternator

I do have rubber motor mounts. Is there some way to insure that the motor is properly grounded to the body?

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