1998 Jeep - Swapped Alternator's and the new one is frying my 20A fuse

[Candymancan]

I know my vehicle isnt a sports car or whatever you guys have on these forums.. But i found a link to this website while doing google searchs on my problem.. The people on jeepforum.com havent a clue so i was hoping you guys could help me.

I have a 1998 Jeep grand cherokee 5.9 liter v8.. It came with a 150A alternator from factory.. The 5.9 Jeep was a very limited number production and because of this they dont have an aftermarket for its one of a kind parts which include this alternator.. I have to downgrade to a 136 for a direct swap... Which sucks.. and all the other 5.9 owners have the same issue.

So there are a few how to threads on how to get around this.. They call for taking the durango/dakota/ alternator from a 5.9 engine which are 160Amps and swapping it to our vehicles.. The only problem is these trucks are from 2001-2005 and in 99+ they changed the pigtail plugs on the alternators to a new standard. But the writeups show how to swap your old pigtail to the new one.. and its pretty simple..

I got 3 pigtails from a JY.. I cut off my old one and proceeded to follow the guide.. The guide called for cutting the ring connector off on the pos and negative cables as well because you need a larger ring connector for the positive bolt on the back of the alternator.. I did that and crimped the connector to the POS wire and also soldered it and taped it.. The negative i did the same thing.. Now the difference between the old alternator and the new one is the old one had a direct ground going to it.. The new alternator doesnt but all the guides say you can just plug the ground to a bolt behind the alternator where there are already a few grounds.. Which i did..

The other 2 wires go to the PCM which is where the voltage regular is "external regular" and something else. The guides claim the order these wires plug up doesnt matter.. The new pigtail had a solid green and a brown/orange wire. Mine were solid green and green.purple.. So i wired both solid greens together and the green.purple to the brown/orange..

I hook it all up and when i turned the key to the on position i had no gauges no power and no gas.. It wouldnt start either just crank.. I checked the fuses and i blew a 20A fuse in the box inside the engine bay which controls the Alternator/PCM/O2 sensor and fuel pump.

I tried a new fuse and same thing blew as soon as the key went to power.. I unplugged the pigtail on the alternator and tried a new fuse and it works and my gauges work, shows battery and fuel level... So the alternator is blowing that 20A fuse when the key is flipped in the on position.. Why is that ?? Did i wire these wires incorrectly ?? I dont see how the alternator could be bad.. Its brand new remanufactured. I dunno, i need my car its been sitting for over a week and ive been carpooling and sharing a car with friends.. I do landscaping so this is my lively hood.. I need this working. The only other thing i can think of is the old alternator ground pluged directly to the alternator.. This one doesnt have that.. But isnt the alternator case itself and the engine it bolts to a ground ? So i dont see why that would matter.. Maybe i should take the ground and bolt it to one of the case mounting bolts ? I dunno

Please help sorry for a long post but i wanted to give as much info as i could.

Here are pics on how its wired. And the link to the writeup.. as you can see its wired correctly i believe ? Maybe i should swap the green wires on the pigtail ? The solid green to the brown/orange and so forth ? I dunno...http://www.jeepforum.com/forum/f13/write-up-durango-160amp-alternator-swap-1330999/

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[Candymancan]

https://books.google.com/books?id=3... check if your alternator is grounded&f=false


Found this.. If you scroll down midway or so you will find the section on Chryslers Computer control alternator's. It mentions both green wires. It says one comes from the 12V ignition source. The other comes from the power module and controls the ground on the alternators field coil.

To me that doesnt sound like those 2 wires are interchangable like everyone i talk too is saying.. but what the hell do i know. Perhaps this is why the fuse pops because the 12V ignition wire is plugged into the ground and the ground is in the ignition source ? So that MIGHT be why when i swap the position of the wires it no longer pops the fuse.. But it doesnt explain why when the Jeep starts the voltage spikes like it isnt being regulated.

The ODD thing is when i first did the wire swap and it stopped poping fuses last night. It started up and the voltage was at 14v right in the middle of the gauge.. and it was running fine for like 2-3 minutes. When i was letting it run idle i went to the engine bay to make sure the alternator sounded right and then then suddenly the lights went super bright and the voltage went crazy. So it was being regulated for a short time it seems . I cant replicate that again as it just turns on and over charges imediatly..


Thats why im here to find out whats wrong. Im bad with electrical so besides following this guide on how to wire i dunno where to find this short... A new used PCM for my Jeep is only 100-200$ it isnt much, but then we have already concluded it isnt the PCM as it works fine with the OEM Jeep 150 and 136 alt.

As for an external regulator. If i do that it will cause a check engine light and i wont pass inspection. Here in virginia they fail you for a check engine light even if its a useless sensor you dont need.



Could the problem be the Power distribution box ? aka The fuse box ?

 

[Candymancan]

Im burned out from this guys.. litterally have my last 2 days off poping fuses cutting wires and spending money on fuses and connectors and crap.

I really appritiate all your help. Tomorrow im going to return this 160a alt and get my 144$ back.. Then ima return this 136A alternator and get my 200$ back.. also return a few ring connector terminals and get 20$ back

Then ima go on advanceautos website and order another 136A for storpickup but use a 30% discount code i have. And returning my dead 150a as the core the price will only be 100$ for the 136A....

Just going to live with the downgraded alternator for now. I have bills to pay and im going broke and i need the money for all these alternators i purchased back. I dont want to buy an external regulator and habe a check engine light which causes more problems with inspection and more headaches.


Im just so dumbfounded to why this 160a wont work in my Jeep but the mod works for others.. sigh..

When i get money saved up im going to splurge and buy a brand new 150A Alternator from quadratec.com only reason why i didnt do that in the first place was because its 220$ and only a 1 year warrenty vs lifetime and going the 160a route was only 100$ after core with a lifetime warrenty.

Sigh... The price you pay for owning a limited production model.. The 5.9 grand cherokees were made only 1 year and only like 10k of them were made.. So sensors. Alternators. Computers. And even the transmissions and stuff replacement parts are non existant.

 

[Dsmkauai]

Yup seems to be why your fuses keep popping. Can't cross power and ground or bad things happen.
There is a tsb on the power distribution box. Might wanna look into that one, call the dealer and ask what's up with that. Quite the list of recalls too .
And I don't remember there being a problem with the check engine light with the external reg. But we only have safety here they don't check the Check engine light or any emissions.
Found this while reading
"Often overlooked- a short-to-ground in the "return" wire (usually green) to the PCM from the alternator can cause the alternator to go into full-charge mode."

 

[Candymancan]

Well the guy from the alternator shop suggested i up the fuse... But ive heard upping fuses is a no-no and can fry stuff.

The PCM remember also runs off this 20A fuse.. I have 30 Amp and even 56AMP fuses this size... but im afraid to see what happens if i put in a 30 amp.. wouldnt i have the posibility of frying the pcm if i do that ?

How hard and what is the process of installing a external regulator ? I know itll cause a check engine light though so like i said come inspection ill have to get around that somehow.