What alternator do I need.......help

[brads70]

I use an electric fan, MSD box, electric fuel pump, stereo, etc...  Last time I drove my car to Carlisle ( 7 1/2 hour drive) the 100 amp alternator I had was not enough and it left me stranded  about an hour from Carlisle when I stopped for gas. I had to get a buddy to drive to the local Walmart and get me another battery to continue and I rewired the electric fan on a toggle switch so I could shut it off when on the hwy so the battery could charge. Around town locally it was never an issue as I usually but the battery on a battery tender when I don't use it as much. I learned that  the electric fans that move the most air also drawn more amperage. 30-50 amps is normal for a good fan. All my electrical add ons are on relays and draw from the battery alternator not the stock wiring. Also as far as I understand it alternators only produce what's needed. My 250 amp alternator does not produce 250 amps all the time only if needed. It has the "capacity" to produce 250 amps.  Have you ever noticed when you turn on A/C or another higher amp draw it draws the motor rpms down, that's because it making the alternator need to produce more amperage.  So having an alternator that is able to produce more than you think you will need is not a problem as long as it's all wired correctly  ( don't use the stock wiring to draw from) I'm not 100% sure but I don't think any new car has a alternator that is rated at 78 amps, they are all much more to supply all the modern electronics.  I just mention this as I really don't think a 78 amp alternator is going to work for you and don't want to see you make the same mistakes I did.   

[70chall440]

I use an electric fan, MSD box, electric fuel pump, stereo, etc...  Last time I drove my car to Carlisle ( 7 1/2 hour drive) the 100 amp alternator I had was not enough and it left me stranded  about an hour from Carlisle when I stopped for gas. I had to get a buddy to drive to the local Walmart and get me another battery to continue and I rewired the electric fan on a toggle switch so I could shut it off when on the hwy so the battery could charge. Around town locally it was never an issue as I usually but the battery on a battery tender when I don't use it as much. I learned that  the electric fans that move the most air also drawn more amperage. 30-50 amps is normal for a good fan. All my electrical add ons are on relays and draw from the battery alternator not the stock wiring. Also as far as I understand it alternators only produce what's needed. My 250 amp alternator does not produce 250 amps all the time only if needed. It has the "capacity" to produce 250 amps.  Have you ever noticed when you turn on A/C or another higher amp draw it draws the motor rpms down, that's because it making the alternator need to produce more amperage.  So having an alternator that is able to produce more than you think you will need is not a problem as long as it's all wired correctly  ( don't use the stock wiring to draw from) I'm not 100% sure but I don't think any new car has a alternator that is rated at 78 amps, they are all much more to supply all the modern electronics.  I just mention this as I really don't think a 78 amp alternator is going to work for you and don't want to see you make the same mistakes I did.   

I agree with Brad on this issue which may seem counter to my original comments; however the point of where I started was/is the wiring issue. If you are running the kinds and quantities of things like Brad is, then yes you will need a big alternator, however you need to have the wiring to support it. That is/was the intent of my original postings. Throwing a 160 amp alternator into a system designed for 60 amps is not going to end well. However if you do it methodically and rewire the components that need it, you will be fine. The point here is that the electrical system is just that, a system and you have to approach it as such. You have to start with the various loads you will or want to place on the system, then decide what size alternator you need, then determine what effect that will have on the other components and associated wiring and make the necessary changes so you don't go up in flames. Unfortunately it seems that Mopar hired the bottom of the class of electrical engineers back in the day or perhaps this was the level of expertise available back then, but Mopar electrical systems leave a lot to be desired. That said, you can make them work and safe so long as you approach it in an organized educated manner. You are on the right track, stay with it and you will get it sorted.

[azievinger]

I hit the same problem an 2 years ago. My setup. Electric fan, replaced headlight to halogen, msd setup and sound setup with amplifier and bass box in the trunk.
So my stock alternator giving 60 or 80 amps of something did not last long, after replacing, still was having issue's.
My solution and since doing all this never had any issue's any more:
Alternator : Powermaster 8-47529, 140 amp
Installed an "capacitor" for the sound. I went with 1 farad
And I went with an optima Gel battery.
I have completely new wiring running in my car.
No issue's any more.
Good luck.

[70chall440]

I hit the same problem an 2 years ago. My setup. Electric fan, replaced headlight to halogen, msd setup and sound setup with amplifier and bass box in the trunk.
So my stock alternator giving 60 or 80 amps of something did not last long, after replacing, still was having issue's.
My solution and since doing all this never had any issue's any more:
Alternator : Powermaster 8-47529, 140 amp
Installed an "capacitor" for the sound. I went with 1 farad
And I went with an optima Gel battery.
I have completely new wiring running in my car.
No issue's any more.
Good luck.

good formula 

[GreenFish]

I did the Mad... amp bypass.
Battery is relocated in trunk but mounted a jy scavenged power block from a Ford. Plenty of fuses and 4 relays. Mounted it up in front of core support. Relays are feeding ele fans, will eventually feed for head lights, also feeding power to full set of instruments.


Wiped of the unwanted logo and spray bombed some texture. Tucks in nice and tight. My low cost option.


Mike.

YT,

Did you pull the wire harnesses too?  How did you connect into the panel? Don't those things have wire harnesses that plug into the underside? I love this idea.

[YellowThumper]

No, I just cut the wires and spliced the needed ones in.
I did however remove many of the wiring connections. The block comes apart to where the terminals are exposed.
I will pull up some pics later to show what and why I did some of it.

Mike

[YellowThumper]

Here is the bottom inside. I ended up removing most of the wires and will add back as required. To elaborate on the comment I made about finding one that was not as heat baked and brittle. There is a small tab that flexes and snaps back to hold the connector in place. The first one I had, numerous tabs just broke when I was trying to get clip to release. Found another that was more pliable that worked. Could have just kept all the wires and connections in but I never take the easy route...



Also this particular piece all the fuses and relays are always hot. They are connected with in essence a buss bar. To correct this I cut off some of the connections on the buss bar to isolate some of the fuses. Those were then powered up with relays triggered with factory ignition and accessory power.
With the buss bar out of the way blade connectors fit the exposed fuse connection.