Stock alternator size (amps)

[bsl2ck]

I have a 2003 TB LT 4x4 with the 4.2l engine. Can someone tell me the amp rating on the alternator?
Thanks

[JR4815D2]

I believe its 150 amps.. but I could be wrong....

[hatchet669]

its either 130 or 150 i think... cant remeber for sure... they ask u thins when u want to replace ur belt... if that is what ur doing... the size difference is only half an inch so just get a belt for the 150... off the top of my head i dont know the code for it tho... someone listed it before i'm sure there chime in

[bsl2ck]

its they ask u thins when u want to replace ur belt... if that is what ur doing...

Thanks for the replys guys. I think I blinked twice and had 2 replies already.

Actually, I'm not replacing anything. I have a number of radios that need to be installed in the car and need to know what I'm working with powerwise from the alternator.

[JR4815D2]

Welcome to the site... You will have tons of info and meet cool people.... So I checked my Chilton books and it's 150 amps

[bsl2ck]

Welcome to the site... You will have tons of info and meet cool people.... So I checked my Chilton books and it's 150 amps

Thanks for the welcome and the information.

[ltbuick]

Check Rpo's
Kg3 145 Amp
Kg4 150 Amp

[hatchet669]

Check Rpo's
Kg3 145 Amp
Kg4 150 Amp

damn i was right the first time on the amp... i knew it was somethign to ridiculous lol

[garym1a2]

Thanks for the welcome and the information.
Just to add one note, alternators are normally rated at 6000 alternator rpm, this is about 2000 to 3000 engine rpm depending on pully ratio. At low rpm that 150 amp alternator may only put out 100 amps.

[bsl2ck]

Just to add one note, alternators are normally rated at 6000 alternator rpm, this is about 2000 to 3000 engine rpm depending on pully ratio. At low rpm that 150 amp alternator may only put out 100 amps.

So, if I am driving along at a "normal" cruise with the tach showing between 1000 - 1500 engine rpm then I should expect about 100 amps? Is that the low rpm range you mean.

The other question I would ask is, if the alternator has the capacity to put out 100 amps at cruise, how much of that is excess beyond the needs of the vehicle? I realize that will be dependent on a number of factors, but are we talking 50%, 25% or more in excess current available to drive other devices (radios in my case)?

Thanks for the information gentlemen,

[garym1a2]

So, if I am driving along at a "normal" cruise with the tach showing between 1000 - 1500 engine rpm then I should expect about 100 amps? Is that the low rpm range you mean.

The other question I would ask is, if the alternator has the capacity to put out 100 amps at cruise, how much of that is excess beyond the needs of the vehicle? I realize that will be dependent on a number of factors, but are we talking 50%, 25% or more in excess current available to drive other devices (radios in my case)?

Thanks for the information gentlemen,

I would say at 1000 rpm you are pulling 2200 to 2600 rpm at the alternator depending on pully size. At 1500 engine rpm the alternator is probally 3300 to 4000 rpm and producing 80% of it's rated power. One thing to watch is in this rpm range the alterator produces decent amperage but not a lot of cooling and hence it will run rather hot if you load it heavy. If I wanted to get better preformance out of an alternator I would put a smaller pully on it and spin it faster. If it was me I was me I would just put in the radios and see watch the voltmeter. If you can keep a decent charge you are fine.

[Coach Steve]

Okay, since nobody else is going to ask...........

".....a number of radios......"

What the....? Do tell, do tell!

[bsl2ck]

Okay, since nobody else is going to ask...........

".....a number of radios......"

What the....? Do tell, do tell!

First, when I say radios I mean 2-way, not broadcast (listen only). Second, by "a number of radios" I mean 6 or 7. There are 3 different 100 watt FM voice radios, on different frecuency bands, and 2 FM radios used for diigital communications (vehicle tracking and messaging). There is also a 100 watt HF AM/FM and SSB radio that is used for other purposes ( for fun). Sorry, no CB. There is sometimes another FM voice radio that I use when necessary. The reason I was asking about the rating of the alternator is that a 100 w radio can pull better than 25 amps when transmitting. Thankfully they are usually only used one at a time in transmit.

So the next likely question is why, right?

I provide emergency communications for a number of groups. My truck is my mobile radio shack.

[longhorn262]

your fine if i can put a 1200 watt amp in my car pulling 80 amps then i think your little 25 amp radios will not drain a thing. plus your batter has up to 600 to 800 cranking amps so if you do go over the power rating from your altanator you will start chipping away at your battery. but then when your not using any power the alternator charges it up quickly so as long as your battery reads above 11 volts your fine. if you dont have enough power which is probably unlikely. just have another battery added to your car. Thats what i ended up doing with my system. cause evertime the amp hit a low note and used the full 80 amps my lights would flash cause for a split second it would use all of the power from my alternator.

[Outback_Jon]

First, when I say radios I mean 2-way, not broadcast (listen only). Second, by "a number of radios" I mean 6 or 7. There are 3 different 100 watt FM voice radios, on different frecuency bands, and 2 FM radios used for diigital communications (vehicle tracking and messaging). There is also a 100 watt HF AM/FM and SSB radio that is used for other purposes ( for fun). Sorry, no CB. There is sometimes another FM voice radio that I use when necessary. The reason I was asking about the rating of the alternator is that a 100 w radio can pull better than 25 amps when transmitting. Thankfully they are usually only used one at a time in transmit.

So the next likely question is why, right?

I provide emergency communications for a number of groups. My truck is my mobile radio shack.

A little bit of ham gear, huh? I'm still trying to figure out a good place in the darn truck to mount my HTX-242... Not a lot of real convenient mounting places.

de KC2BNE