Alternator Upgrade?
Champion
Joined: Jan 2013
Posts: 4,737
Likes: 374
From: Northwest Louisiana
Hey Ralph,
I "think" the big 3 you were talking about is basically upgrading the postive cable, negative cable, associated grounds, and the alt. feed to a larger size... Is this correct?
I cant find a listing in my FSM showing ga. size of the cables....
Assuming I can use the 120 amp alternator, would you mind answering the following questions?
1. What size neg. cable to battery?
2. What size pos. cable to battery?
3. What size feed from alternator? I believe you already said, "at least a 4ga. on that one"
FWIW, I believe I can get the 120 amp through advance auto for about $80.00.... but another concern is, the 120 used an external fan vs the 78 using an internal fan.... Hopefully it will mount up, and the pulleys will align...
I "think" the big 3 you were talking about is basically upgrading the postive cable, negative cable, associated grounds, and the alt. feed to a larger size... Is this correct?
I cant find a listing in my FSM showing ga. size of the cables....
Assuming I can use the 120 amp alternator, would you mind answering the following questions?
1. What size neg. cable to battery?
2. What size pos. cable to battery?
3. What size feed from alternator? I believe you already said, "at least a 4ga. on that one"
FWIW, I believe I can get the 120 amp through advance auto for about $80.00.... but another concern is, the 120 used an external fan vs the 78 using an internal fan.... Hopefully it will mount up, and the pulleys will align...
For my 1988, I look at the charging circuit, and it says that fusible link was 14ga for the 78A, 40/90 alternator and 12ga for the 120A alternator.
It also says on page 8W-51 that the 120A got a 6 gauge wire from the alternator; the 90A a 8ga wire.
I'd do welding wire in 0 gauge; cheap, has high heat jackets, can be had as off fall from welding supply stores fairly cheap, and it's flexible.
Barring that, I've got a guy on EBay that does a bangup fine job if you tell him the lengths - Goes by powderperform, https://www.ebay.com/usr/powderperfo...53.m1438.l2754 . NOT the only source, but so far I've been very happy with the quality of his cables. (I need to measure for my Dakota positive and for two of the cables for the Cougar for him ... )
RwP
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Record Breaker
Joined: Jan 2014
Posts: 1,852
Likes: 109
From: Va
Yes, that is what I have mainly been looking at.... Funny thing is, they do not even show the 78 amp on the dakota, but it was used. Hopefully the 120A will bolt up without needing different brackets, offsets etc.
But thanks for your suggestion.
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Record Breaker
Joined: Jan 2014
Posts: 1,852
Likes: 109
From: Va
For my 1988, I look at the charging circuit, and it says that fusible link was 14ga for the 78A, 40/90 alternator and 12ga for the 120A alternator.
It also says on page 8W-51 that the 120A got a 6 gauge wire from the alternator; the 90A a 8ga wire.
I'd do welding wire in 0 gauge; cheap, has high heat jackets, can be had as off fall from welding supply stores fairly cheap, and it's flexible.
Barring that, I've got a guy on EBay that does a bangup fine job if you tell him the lengths - Goes by powderperform, https://www.ebay.com/usr/powderperfo...53.m1438.l2754 . NOT the only source, but so far I've been very happy with the quality of his cables. (I need to measure for my Dakota positive and for two of the cables for the Cougar for him ... )
RwP
It also says on page 8W-51 that the 120A got a 6 gauge wire from the alternator; the 90A a 8ga wire.
I'd do welding wire in 0 gauge; cheap, has high heat jackets, can be had as off fall from welding supply stores fairly cheap, and it's flexible.
Barring that, I've got a guy on EBay that does a bangup fine job if you tell him the lengths - Goes by powderperform, https://www.ebay.com/usr/powderperfo...53.m1438.l2754 . NOT the only source, but so far I've been very happy with the quality of his cables. (I need to measure for my Dakota positive and for two of the cables for the Cougar for him ... )
RwP
Ralph, I totally forgot about the fusible link...
In short, would it be ok to disconnect the alt. to battery wire, and just tape up the end going to the alternator. Then run a 6 or 4 ga. wire from the alternator to the pos. bat. post, and of course putting a 12 ga fusible link in between?
As I have said earlier, I hope this is all done just for a short while. I hope to put a 5.9 magnum in this winter. At that time I will rework the factory harness.
I am going to start another thread on what I have done with the fans....
Again, thanks for all your help and opinions!!
Champion
Joined: Jan 2013
Posts: 4,737
Likes: 374
From: Northwest Louisiana
If you're doing that, I'd opt for installing a MegaFuse(tm) holder and, say, a 150A or so MegaFuse in the line.
Amazon shows this as a possible pair: https://smile.amazon.com/Spartan-Pow.../dp/B06Y4C6DQR . Note: As always, that's not a "Ya gotta buy it there!" but "Hey, this is what you're looking for".
(They also sell other holders and the MegaFuse separate; one advantage to the MegaFuse is that you can find replacements at places like AutoZone.)
But yes; just be sure to tape the free end up well. Or just trace it back out and cut it completely out of the circuit.
You might want to go ahead and wire up an external adjustable regulator, too; I ran into a write up that included the field replacement resistor value (10ohm 50watt; those can be had off Ebay or Amazon also) so as to keep the ECU happy thinking it's doing the work of regulating the alternator, thereby avoiding the CEL. If not now, I'd consider doing that when you do drop in the 5.9 .
Edit: Don't forget a matching wire from the block to the chassis / frame also; both sides need to be bigger to handle the higher current! While doing the 5.9, consider some welding cable for your main cables; they can be had cheaply as remnants or off fall, and are nice and flexible.
RwP
Amazon shows this as a possible pair: https://smile.amazon.com/Spartan-Pow.../dp/B06Y4C6DQR . Note: As always, that's not a "Ya gotta buy it there!" but "Hey, this is what you're looking for".
(They also sell other holders and the MegaFuse separate; one advantage to the MegaFuse is that you can find replacements at places like AutoZone.)
But yes; just be sure to tape the free end up well. Or just trace it back out and cut it completely out of the circuit.
You might want to go ahead and wire up an external adjustable regulator, too; I ran into a write up that included the field replacement resistor value (10ohm 50watt; those can be had off Ebay or Amazon also) so as to keep the ECU happy thinking it's doing the work of regulating the alternator, thereby avoiding the CEL. If not now, I'd consider doing that when you do drop in the 5.9 .
Edit: Don't forget a matching wire from the block to the chassis / frame also; both sides need to be bigger to handle the higher current! While doing the 5.9, consider some welding cable for your main cables; they can be had cheaply as remnants or off fall, and are nice and flexible.
RwP
Thread Starter
|
Record Breaker
Joined: Jan 2014
Posts: 1,852
Likes: 109
From: Va
You might want to go ahead and wire up an external adjustable regulator, too; I ran into a write up that included the field replacement resistor value (10ohm 50watt; those can be had off Ebay or Amazon also) so as to keep the ECU happy thinking it's doing the work of regulating the alternator, thereby avoiding the CEL. If not now, I'd consider doing that when you do drop in the 5.9 .
RwP
The 87 used an external regulator, along with a carb. Which is one of the reasons, I thought I would use a carb on the 5.9 magnum.... To make it simple "at least for me" vs fuel injection....
Here is a picture of my regulator. Do you think this will work with the 120A alternator, vs the 78A that come on the truck?
Thanks again, and thanks for the link to the 150A fuse....
Champion
Joined: Jan 2013
Posts: 4,737
Likes: 374
From: Northwest Louisiana
They apparently are; I did pick up an adjustable unit to convert my truck (I'm not happy with how the voltage bounces around going down the highway - 14.3 to 14.7 and back according to the digital, and a continuous nervous twitching of the needle on the factory voltmeter).
Also the 10 ohm 50W resistor to fool the ECU.
RwP
Also the 10 ohm 50W resistor to fool the ECU.
RwP
Amateur
Joined: Mar 2018
Posts: 40
Likes: 0
I swapped my alternator to a 120A a couple of months ago. I didn't change any of the wires around it and I haven't had any problems with it. My 120A alternator has a slightly bigger case than the 90A that was stock, but the bolt holes lined up no problem.
Did 87s have 7 rib pulleys? My 95 does and I had to get it swapped from old to new.
Did 87s have 7 rib pulleys? My 95 does and I had to get it swapped from old to new.
Champion
Joined: Jan 2013
Posts: 4,737
Likes: 374
From: Northwest Louisiana
87s were V-belt, as were almost all the LAs (the very last 1991s were serpentine.)
Magnums are serpentine belt.
At least, from the factory.
The 120 I have now also bolted right up; however, for optimum performance, the larger gauge wire is highly recommended.
RwP
Magnums are serpentine belt.
At least, from the factory.
The 120 I have now also bolted right up; however, for optimum performance, the larger gauge wire is highly recommended.
RwP
Thread Starter
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Record Breaker
Joined: Jan 2014
Posts: 1,852
Likes: 109
From: Va
I swapped my alternator to a 120A a couple of months ago. I didn't change any of the wires around it and I haven't had any problems with it. My 120A alternator has a slightly bigger case than the 90A that was stock, but the bolt holes lined up no problem.
Did 87s have 7 rib pulleys? My 95 does and I had to get it swapped from old to new.
Did 87s have 7 rib pulleys? My 95 does and I had to get it swapped from old to new.
As Ralph said, 87 used 2 v-belts.... But I wonder and hope, the 2 are interchangeable with a pulley swap. I hate buying an alternator then swapping motors this winter to find out it will not fit. But that is usually my luck!!