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new alternator

2K views 8 replies 4 participants last post by  nwmod39 
#1 ·
I am finally wrapping up the 350 swap in my 91 astro.
The stock alternator is making a bunch of whining noise and it struggles a little bit when the electric fan kicks on.

I am looking to replace it with a new one with a higher amp rating than the stock one. I have start to do a little bit of research as to what I would need but figured someone in here could give me a solid idea.

Mostly stock van. Standard headlights and running lights as well as a tv, dvd, and lighting in the conversion area.

Anyone have any expert advice as to what rating I should go for. I have read a couple items saying something in the 140 amp area would be good.

Thanks in advance for any help.
Steve
 
#4 ·
The "big 3" upgrade should be done regardless.
The amperage capacity of the alternator will have no effect on the other circuits as they are fused for the amperage they can carry.
A 200 amp alternator does not increase the value of any circuit, they will draw only what is needed for the load.
The bigger alternator will allow you to add more circuits and allow those existing to run more efficiently.
Almost always you'll want a separate new circuit for added toys! Tapping into existing wires, say to run a 12v outlet in the back is not a good idea. You can find an always hot in the back for our interior lights. If you tap into that wire for a phone charger it would probably be fine but it will smoke when you plug in that new cooler fridge unit for the tailgate party.

In my case I have too many added circuits, engine fans, lights, and stereo that if run at the same time stretch the limits of the stock alternator. (my voltage meter drops off more than I'm comfortable with as things are turned on)
 
#5 ·
Remember high amp alternators don't charge as well as lower amp ones at low RPM's. Vans have a notorious voltage gauge issue which is misleading.

Things to consider when getting a new one. Do I actually need it (gauge issue). And do I idle around in town alot so a bigger one may make things worse.
 
#7 ·
I am running the "stock" 110amp (from the V6) alternator on my V8... and I have NO issues whatsoever, running A/C on high, headlights on, with 3300cfm electric fan. I'm all for upgrades... but I just haven't needed one here personally.

IMG_1224.jpg

The headlights, A/C, and electric fan shouldn't draw more than roughly 50-60amps total. That leaves plenty of room for more. If you're running multiple fans.. then you may have more of an issue getting close to or exceeding maximum output. Always a good idea to have extra so you're not running at full sustained maximum output! This is where a stock mechanical fan (with the stock system) has an advantage, except they don't fit well with V8's!

But understand that NO alternator will put out FULL current at idle, which is where you may notice your problem. A strong battery is very important too.

WoodButcher said:
A 200 amp alternator does not increase the value of any circuit, they will draw only what is needed for the load...
This is quite correct BTW... the "load" is what determines the amperage draw ... if the alternator is capable of supplying whatever is needed. :D
 
#8 ·
Same deal here. Same alt and things running on it. I test at the battery. Battery always has a full charge when off sitting overnight.

Idling with brights on, fan running, air conditioner on, stereo blaring. All electrical draw I can turn on. At idle that alt is charging shows 13.8 volts at the battery.

Now the dash gauge is showing it isn't. And that is another tale to tell.

I have still been in the eternal search for the gauge issue. I know I have full voltage in the interior when it is cold and just started but after it has been running it drops. Turning on things makes it drop. A/C or fan or headlights. All tested with a multi-meter. Gauge has been out and tested it is accurate.

Now all GM shares the same electrical switch on the column. I did find a guy who disected a switch for this issue. It feeds engine power on one set of contacts. And interior accessories from one pin which splits into 2 out pins. So it is overloaded basically from the word go. That contact burns and gets high resistance. Affected by heat caused by load which drops the voltage. Which is why the computer and engine are uneffected by this issue.

Which is in the what have you done to your van catagory. I do the major stuff motors and paint report in threads. Then go to trying to solve the smaller no problem just annoying stuff.
I think a additional relay there to supply power to interior. save wear on that switch. And once wired in would be easily replaceable. But again the wires are as buried as they can get. i do not feel like stripping the dash and dropping the column just to have a accurate gauge, So it will wait till it is worse and unavoidable.
 
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