need alternator help asap please!

Just recently bought a new alternator (165A) from alter start and also purchased a new power cable. I'm working on installing it right now and have a question. I searched and couldnt find exactly what I was looking for. I'm almost postive that the power cable is the one located on the "top" with the black 'shield' around it correct. Following that cable leads to a connection about half way to the PDC box. Whats this for? My new cable doesnt have anything on it (its just a straight 4 guage cable). Is the main power cable supposed to be fused??

Also, the other cables dont need to be upgraded, correct? There seems to be four other connections.

There are either three or four connections on the back of an ND alternator (1991-up XJ) - one for the power output, two for the field coils, and one for the ground (this one may not be on the alternator proper, but on the engine somewhere near the alternator. The alternator may also be grounded through the case and mounting.)

From the factory, there is fuse protection in the alternator output circuit - either in the form of two 60A MAXI fuses in the PDC proper, or as a fusible link wire going into the bottom of the PDC.

When replacing the alternator output lead with anything other than OEM, the replacement lead may be run to the same stud where the battery connects (since it's just the end of the Buss bar anyhow) and that is, electrically speaking, the same thing.

However, I find it safe to assume that the OEM fuse protection is there for a reason - I've not run across a blown one, but having the alternator "surge" on you would blow just about all of your solid-state electronics with the current and/or voltage spike. This is why I offer ANL kits for my battery mains upgrades - this allows you to restore fuse protection in that circuit, and it also allows you to upgrade the fuse protection to take full advantage of an upgraded alternator (since the OEM fuse protection seems to top out at about 120A anyhow - generate more than that, and you're going to blow a fuse.)

How can the alternator "surge?" The output of the alternator is regulated by the supply of voltage/current to the field coils (that pair of terminals.) Field voltage almost never exceeds four volts, except in unusual circumstances (a "weldernator," for instance. Or, a high-output alternator make take up to five or six volts.)

An alternator "surge" would be caused by the supply of excessive voltage to the field coils - either by a short "through" the regulator (supplying full battery voltage to the field coils) or by a "battery voltage" lead falling onto a field terminal (supply full battery voltage to the field coils.) Supplying +12VDC to the field coils will at least triple the full output of the alternator - resulting in a race among components to see who melts down first. However, you're gonig to lose all of your solid-state goodies, since that large current spike will probably be accompanied by a surge in voltage to somewhere around 80VDC or so...

Fuses may carry voltage ratings, but they're current-sensitive devices, which is why you select them carefully. The flow of current along a conductor results in heat (among other things) and the conductor in a fuse is designed to melt and separate when that current flow/heat level is exceeded - that's how it works.

The two field connections don't need to be upgraded, but the ground should be (no point in being able to source that much current if you can't sink it - and for this purpose, the alternator is the core of the circuit. Therefore, the ground to the alternator should be at least the same size as the output lead - so check.

If you'd talked to me before, you could have found all of this out before you spent any money... :compwork:

5-90

hmmmm....well thats a little bit bad. My Jeeps been down for about a week now waiting on the new alternator, battery, and battery cables....and I need to get it going. But probably dont want to take that risk though without a fuse. How fast could you get some cables, and how much money

one more question....why do companies sell the cable without a fuse then? Do a lot of people run them without just on the risk and hope that their alternator doesnt "surge?"

Check my site for pricing, although I do need to rework the ANL kit for later models. (Link in sig.)

I ship USPS/Priority Post, so it's only two or three days to the rest of the country.

I have ANL fuses and blocks on hand (you'll either want an ANL150 or an ANL200 - I do need to restock on ANL175's) and I'm waiting for 3/8" 1AWG rings.

You can probably get away with running without the fuse for a while, but I'd keep it light until you get protection installed. I ran my RENIX for a year or so without a fuse, and with a 180A Delco without trouble - but I did end up developing the ANL kit on my 1988... So, if it were mine, I'd go ahead and install it all and plan on getting a fuse in soonest - but that's just me, and I'm not advising you to do it that way. (I'm starting to speak "officially," so the disclaimer is mandatory.)

Your alternator - whatever the rating - doesn't put out full rated current all the time. The voltage regulator will keep the alternator output to what is needed - it probably spends most of its life making 40A or so to keep everything going, unless you run a batch of lights or power supplies consistently. My 180A Delco practically lives under 100A - but it's nice knowing the potential is there if I need it...

5-90

I am seriously at a loss here....after tracing the output wire into the PDC box (fuse box) where it goes into from underneith I cant figure out how to disconnect it. I assume it would be better to disconnect it whether then just leave it hang there and connect the new cable from the alt straight to the battery but I can't figure out how...am I being stupid about something? It seems as though it would just have a connector on the end of it and pull straight out but it doesnt seem to want to come out? I dont want to pull on it too hard if thats not right, anybody know?

Look for a "fat" section of the wire - that would be either a "pull apart" or a "twist lock" connector, so the subharness can be swapped.

Failing that, I've been known to cut the wire short and coat the end with something - like dip vinyl or RTV black - to seal the end. Just don't cut it flush - it's a pain to get to, and you may find another use for it later...

5-90

northwestxj,
What year is your Cherokee?
I just upgraded my alternator, battery and cables over Thanksgiving.
I have a '98 and could tell you where to look if you have a '97+.
Steve
PS. 5-90 makes good cables...

I actually have a 93....I figured out mostly everything, I just need to finish up. I am actually just going to go tomarrow to the parts store and pick up a fuse and splice it into my existing power wire, beings that I already have it. Hopefully should be up and running tomarrow. Thanks for you guy's help though.