alternator/Volt gauge question
Thread Starter
Melting Slicks
Joined: May 2000
Posts: 2,305
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From: Orlando,Fl,USA
alternator/Volt gauge question
This sounds stupid but dosn't the volt gauge usually go towards the positive side when reving the engine up. Mine is going slightly the otherway? This happens even with all the accessories off. I had the battery & alternator checked on the bench at a local pepboys & they said it was good. This is the second powermaster 100 amp alternator in this car. It is wired with a 6gauge wire directly to the starter/batt post. It seems to be holding battery power but voltage will drop off severly when lights & a/c are on. The a/c is really the biggest drain and the volt gauge never goes above the middle when operating at any speed.( that is when A/C is on) If its on high blower it will pull volts to the negative side. I do have a aftermarket A/c system. I will get a positive volt reading about 14 when cruising without anything else on(i.e. A/C, lights) The problem was solved when I first changed to the high amp alternator but has deteriorated a few months afterward. My first pwr master alternator burned out a diode withinn 2 weeks of service and I'm almost on my 2nd year with the 2nd one. I was wondering if its the guage?? How can I test this.
Last edited by dogboy; Oct 17, 2004 at 10:08 AM.
Race Director
Joined: Sep 2004
Posts: 11,874
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From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
positive side??? on a volt gauge? is this an ammeter or a volt gauge? what yr is the car. if its a volt meter perhaps ( it may move to the right),if its an ammeter depends on the draw from the appliances that are on the car. if there are no appliances on, it would probably stay relatively in the same place i would think.
sounds to me like you have an ammeter and are use to seeing it show a positve needle position after you start the car up ,showing its charging the battery. and this happens at higher revs....once the battery is charged the needle position probably will be neutral or in the middle of the gauge.
sounds to me like you have an ammeter and are use to seeing it show a positve needle position after you start the car up ,showing its charging the battery. and this happens at higher revs....once the battery is charged the needle position probably will be neutral or in the middle of the gauge.
Last edited by bobs77vet; Oct 17, 2004 at 10:48 AM.
Race Director
Joined: Sep 2004
Posts: 11,874
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From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
i have a 77, and when i turn on the ignition the volt meter reads 12 volts, this makes sense since its reading the voltage from the battery, when i start the car and rev the engine the voltage goes up, which it should. if your car is similar and the voltage readings are similar, i would think your gauge is working ok. when you turn all the appliances on, i could see a drain on the system and the voltage going down. could you have a system that is drawing too much amperage?? I would check the amp ratings on the aftermarket ac system for starters and then add up the rest of items that are drawing current and compare this to your alternator output.
