My charging system symptoms denotes alternator failure - yes?

[AuroraGirl]

i made another thread about what alt to use.
I guess, after some more reading, I need to make sure thats actually the issue

The gauge is correct when I say these values, by the way, that i did verify.

I start truck, it will hang around 12v on gauge. overtime it will drop to about 8. If i rev it and keep it high RPMs, it will read around 13.
But it will go back toward 8. It does discharge over time, and batteries have been healthy.

I dont have a red light on my cluster light up with Key on for the alternator gauge, it has a warning light spot on the face thats obviously in that gauge, but ive never seen it light up.

truck has a 10si. I have not inspected the junction box but i will in morning when i swap alt bracket(gotta be changed no matter what, alt is just something i planned to do too) what should i look for if my symptoms arent alternator? to me it makes sense, at high RPM its outputting what it should at idle, at idle its too low. Its worn out. but maybe im wrong?

 

[SirRobyn0]

My instinct is your right your alternator is failing..... But. the factory alternators back when these trucks were made were not the best at putting out at idle. Even today's vehicles when testing an alternator it's usually done at 1,500 - 2,000rpm. Unless all your doing is idling it shouldn't discharge the battery. If you had some way to measure to measure the amperage the alternator is producing that would be the thing that would tell you for sure if it's failing. But even if you can't test the amperage, if voltage is dropping off sharp at idle and battery is discharging, I'd go ahead and replace the alternator.

 

[AuroraGirl]

My instinct is your right your alternator is failing..... But. the factory alternators back when these trucks were made were not the best at putting out at idle. Even today's vehicles when testing an alternator it's usually done at 1,500 - 2,000rpm. Unless all your doing is idling it shouldn't discharge the battery. If you had some way to measure to measure the amperage the alternator is producing that would be the thing that would tell you for sure if it's failing. But even if you can't test the amperage, if voltage is dropping off sharp at idle and battery is discharging, I'd go ahead and replace the alternator.

Hmm. Im pulling that bracket off other engine today and have oogles of 10si laying around so i can just try those haha! If i see a difference i will know

 

[Matt69olds]

Before you do anything, verify the charging system voltage with a meter. Then check the charging system voltage on the battery cable stud on the back of the alternator. The factory gauges aren’t the most accurate, but usually read fairly close. It’s best to verify you actually have a problem before trying to fix it.

 

[AuroraGirl]

Before you do anything, verify the charging system voltage with a meter. Then check the charging system voltage on the battery cable stud on the back of the alternator. The factory gauges aren’t the most accurate, but usually read fairly close. It’s best to verify you actually have a problem before trying to fix it.

i did. I said that in my post. i verified the gauge reading was on and to clarify i did use voltmeter. I actually just took off my bulkhead and my connector ON the alternator dont look.. wonderful but they dont seem bad. thoughts on connections as far as solid goes? Im going to clean the contacts with contact spray and reinstall

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[AuroraGirl]

I was just showing the grounds for engine/battery and power cables, they are cleaned up except on starter but that hasnt been an issue so i didnt touch it.

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the part of the alternator the wire connects to looks burnt. and the belt had misalignment because of bad bracket(its what im changing) and im guessing that wrecked hell on the bearing and made it loud. I found one on my shelf that says "GOOD" and has a nice quiet, no play bearing. I think its hardly used, its also delco remi so original probably. says sunfire. If yall think connections are okay I am gonna reconnect stuff cleaned up and try it, see if it makes a difference

 

[Matt69olds]

I went back and re-read your post, I see where you said you verified the problem with the gauge follows the actual system voltage. My apologies.

If the sunfire alternator will bolt up, it’s pretty easy to adapt the wiring if you have the correct plug. Post a pic of the alternator plug in. If you don’t have a plug, I’d bet there are plenty in your nearest salvage yard, or maybe available thru Dorman or Help at the parts stores

 

[AuroraGirl]

Its a 10si, its exactly the same. i run into an issue tho, i need belts. i will be buying those while at workj

 

[SirRobyn0]

i did. I said that in my post. i verified the gauge reading was on and to clarify i did use voltmeter. I actually just took off my bulkhead and my connector ON the alternator dont look.. wonderful but they dont seem bad. thoughts on connections as far as solid goes? Im going to clean the contacts with contact spray and reinstall

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I think i agree with your own thoughts, most of the connections done look the best, but I've seen worse still working. I think if it were me I'd do what I can to clean them up at least the bulkhead connector since you have it apart, I wouldn't go to any extreme lengths. A quick clean and if you have dielectric grease put some of that on the terminals as it will help prevent or at least slow deterioration.

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[Ricko1966]

I don't have all trucks/cars andcalternators memorized so I can't give you more specifics. Was your truck supposed to have a chargingvsystem warning light and a gauge? If so fix the dash warning light first thing, in many cases the alternator will not function. Without a functioning dash light because it provides voltage to the field windings. Some won't charge at all some won't charge correctly.My gut says you are suppose to have a light to excite the field windings.Just cause it works at high rpm doesn't indicate the light is not the problem. You can look at a schematic for your truck and verify this by using a test light as a temporary idiot light.Usually it's battery power from a key on source to a light bulb to a post on the alternator.In that cast it would be for test purposes battery+ to light to appropriate pist on alternator.

 

[Goldie Driver]

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Bad alternator.

Here was my gauge the DAY I got it and had to drive her home - not the plan. Anyhoo, never noticed this until later. I think the next day or two I changed it out when she wouldn't start ...

 

[Bextreme04]

Why not just take it off and take that one and the one that says good to the parts store. Most will test your alternator output for free. If you already need belts, just take both in and get them tested when you buy the new belts.

Mine often reads a little low. When I first got it, it would read down to 8 or 9v when the headlights were on. My idle was a little low and raising it up to around 800rpm made a world of difference. Now it stays up in the 12-14v range all the time unless idling for a long period of time with headlights on.

 

[Ricko1966]

10si batt goes to batt+ #1 goes to a keyed light #2 goes to 12v constant. So check for 12v at batt on alternator.. Check for 12v. On # 2 at alternator #1 stick your test light on it hook the test light to battery positive. Light should be lit. Start the truck light should go out. Now look at your gauge.