Problem - Alternator or battery?
Thread Starter
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Fleet Mechanic
Joined: Apr 2008
Posts: 1,724
Likes: 2
From: Vancouver BC Canada
I have a digital multimeter. I quickly put it on the battery yesterday with the + and - on the corresponding terminals and the dial set to 20v. The meter simply read 1. so I think I must be doing something wrong.
Senior User
Joined: Oct 2003
Posts: 480
Likes: 1
From: Elyria, Ohio
As stated previously, make sure your voltmeter is set up to read DC voltage, 20V scale is good. It is not a good idea to remove the positive cable while the engine is running. These alternators have a sensing wire to battery voltage. The regulator will increase output without this feedback circuit. There are numerous references to this in these forums (search). There is always someone who gets away with it and is lucky to get it to work without incident, and it was a valid procedure for the days of generators on vehicles. But you don't need 20+ volts surging to your circuits and your computer. Measure it with your voltmeter or have an auto parts store load test the battery and test the alternator on one of their in house diagnostic instruments.
Posting Guru
Joined: Aug 2007
Posts: 2,026
Likes: 0
From: Belle Mead NJ
There is nothing wrong with either, this is commin to most older stuff, I have the 130amp alt in my 88 stang, 88 bronk, and 95 F350, and when ideling with lights, wipers, radio and heat on(no ac in all lol) the bat meter goes down. The alts just cant put out the load that it needs at idle, needs the revs to make more power. I have dual batteries and the 130amp in the F350 and it does it. Its life. You are better off going to a autozone or where ever and have them put the machine on your truck, it will test the CCA(cold cranking amps) off the battery, whats its rated for, and what it really has, will also tell you the % of life and charge of the batter. That tool can also test the alt, volts with load on and load off, idle and revs. We have an awesome 1 at our job.
New User
Joined: Mar 2010
Posts: 2
Likes: 0
going to try a load test...
thanks... will post results this what seems like lack of power for such a simple task is driving me crazy, never mind my mechanic.
keeps continuing and I will need to re-think keeping my flareside.
thanks... will post results this what seems like lack of power for such a simple task is driving me crazy, never mind my mechanic.
keeps continuing and I will need to re-think keeping my flareside.
Thread Starter
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Fleet Mechanic
Joined: Apr 2008
Posts: 1,724
Likes: 2
From: Vancouver BC Canada
As an update, had the battery tested and it's fine. Found a sale date on it and it's only 2years old. Going to upgrade the alt and replace the positive battery cable.
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