[semi rant]Alternator bench test......
Thread Starter
Melting Slicks
Joined: Jun 2001
Posts: 2,808
Likes: 0
[semi rant]Alternator bench test......
.....aint worth sheit! My voltage has been reading 11.6 on startup and climbing to a max of 12.6 under normal driving conditions. If i turned on any acc. the voltage would drop to 11.7. I removed the alt. went to auto zone for a bench test. which their 'bench test' showed the alt to be good.
I have fought with this car for the last two weeks,(in my spare time), trying to find where in the circuit the problem was. Finally after finding nothing, like loose connections or burnt wires, I just decided to replace the alternator, I figured i would start there with replacing parts till i got it fixed.
And GOLLY GEE! guess what, It worked.
I started the car after installation, and the voltage read 14.2. I then turned on some accs and still the same 14.1 @ idle. All was fine under normal driving also.
I just wanted to share this, and make aware not to put a lot of trust in those so called "bench test", like the ones at Autozone and so fourth.
[Modified by mikes84vette, 5:53 PM 5/24/2002]
I have fought with this car for the last two weeks,(in my spare time), trying to find where in the circuit the problem was. Finally after finding nothing, like loose connections or burnt wires, I just decided to replace the alternator, I figured i would start there with replacing parts till i got it fixed.
And GOLLY GEE! guess what, It worked.
I started the car after installation, and the voltage read 14.2. I then turned on some accs and still the same 14.1 @ idle. All was fine under normal driving also.
I just wanted to share this, and make aware not to put a lot of trust in those so called "bench test", like the ones at Autozone and so fourth.
[Modified by mikes84vette, 5:53 PM 5/24/2002]
Pro
Joined: Jan 2002
Posts: 596
Likes: 0
Re: [semi rant]Alternator bench test...... (mikes84vette)
I work at such a place, though not Auto Zone, remeber that though bench testing is for the most part accurate, it CANNOT simulate true engine bay conditions, such as heat, loose alt. belts, etc. Such conditions can affect a alternators performance. I don't mean to bash, as I understand thats frustrating, and their bench indeed may of been defective, just wanted to present some food for thought.
Melting Slicks
Joined: Apr 2000
Posts: 2,793
Likes: 46
From: Elizabeth City, NC
Re: [semi rant]Alternator bench test...... (Oh My)
I don't generally trust them either, you can only hope to have a counter person that is concerned enough to realize that their test CAN be wrong on occassion. :smash:
Thread Starter
Melting Slicks
Joined: Jun 2001
Posts: 2,808
Likes: 0
Re: [semi rant]Alternator bench test...... (Oh My)
I work at such a place, though not Auto Zone, remeber that though bench testing is for the most part accurate, it CANNOT simulate true engine bay conditions, such as heat, loose alt. belts, etc. Such conditions can affect a alternators performance. I don't mean to bash, as I understand thats frustrating, and their bench indeed may of been defective, just wanted to present some food for thought.
Their test showed a little above 14 volts.
Drifting
Joined: Mar 2001
Posts: 1,636
Likes: 3
From: Lafayette IN
Re: [semi rant]Alternator bench test...... (mikes84vette)
Does this test place a load on the alternator? Or does it just spin it at so many rpm's and measure voltage output at that piont.
Their test showed a little above 14 volts.
Their test showed a little above 14 volts.
I usually opt for the on-car test, but for a Vette, that usually requires having the gill panel (the one you take out to replace the battery) removed because of the location of the cables and trying to get the inductive pickup on correctly.
Thread Starter
Melting Slicks
Joined: Jun 2001
Posts: 2,808
Likes: 0
Re: [semi rant]Alternator bench test...... (Oh My)
I work at such a place, though not Auto Zone, remeber that though bench testing is for the most part accurate, it CANNOT simulate true engine bay conditions, such as heat, loose alt. belts, etc. Such conditions can affect a alternators performance. I don't mean to bash, as I understand thats frustrating, and their bench indeed may of been defective, just wanted to present some food for thought.
Safety Car
Joined: Feb 2002
Posts: 4,286
Likes: 4
From: Guam
Re: [semi rant]Alternator bench test...... (mikes84vette)
The bench test method does not take in to account the various loads that a car goes through. A voltage regulator sometimes acts differently as the loads increase or decrease. With a slight load it may appear to be putting out sufficient voltage. But as the load increase, it may fail. I would suspect that the voltage regulator in your old alternator is defective. :D
Pro
Joined: Jan 2002
Posts: 596
Likes: 0
Re: [semi rant]Alternator bench test...... (Sharky Guam)
The bench test method does not take in to account the various loads that a car goes through. A voltage regulator sometimes acts differently as the loads increase or decrease. With a slight load it may appear to be putting out sufficient voltage. But as the load increase, it may fail. I would suspect that the voltage regulator in your old alternator is defective. :D
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