CLSegraves1

I recently removed the mechanical fan from my 2001 XJ and converted it to use 3 electric radiator fans. To do this, I used the Dirtbound aluminum shroud and 3 ebay 10" fans (because I wanted to be cheap). The result was an immediate improvement in both AC and radiator performance. Before the swap (now that it's over 100 degrees outside), the AC was horrible in stop/go traffic or when out crawling and the engine temps would sit above (not much, but slight) the 210 mark. Now the AC blows ice cold and coolant temp never reach 210 (stock T-stat and radiator).

All good right? Nope, the problem is the XJ comes with a crappy 90 amp alternator. I could literally watch the voltage gauge inch its way down sitting in traffic (at idle). To make matters worse, I haven't yet added lights, a winch, etc.... you know, all the toys that every red blooded American should have on their Jeep. So, something had to be done....

The easy solution is to get a 136 Amp alternator from a Grand Cherokee (direct swap), but I've never been one for taking the easy route. Instead, I decided to go for the big gun and get myself a 160 Amp alternator from a 2002 Dodge Durango. A quick search on car-parts.com located one at a local wrecking yard for $50 (+$5 with no core). After picking it up, I stopped by O'Reilly and had them check it on their machine to confirm it was good. I sure was happy when the "PASS" messages flashed up on the machine's screen!

Install/Making it fit:
As I understand, for the 1999+ XJ's it's an electrical direct swap (my 2001 had the same plug as the Durango), however earlier XJ's will need to change their alternator plug (or rewire if you have an external regulator). The mounting bolts are the same, but the Durango alternator case is physically bigger than the XJ's alternator. It's not by much, but enough that you can't just remove one and install the other. It requires grinding a little off both the bracket and the engine block. It's not hard (if you have a decent die grinder and a carbide bit) and only took me 30 minutes. The attached shots show the amount I ground on the XJ's brackets. I ground more than was absolutly necessary, but I wanted to ensure I NEVER had an issue (ie: need a replacement in the future and it turns out being minimally larger). Once the grinding was complete, the alternator slipped in like factory.

Pulley Swap:
I also swapped the alternator pulley from the XJ alternator to the Durango alternator. The XJ pulley is 2" while the Durango pulley is 2.25", so the XJ pulley will spin the alternator a little faster and further improve idle/crawling amperage output (I'm considering digging up a 1.75" pulley as that would give even more boost to idle/crawl amperage, but I'll wait and see).

Wire Upgrade:
The factory alternator cable is pathetic at best (looks to be 4 gauge). To make matters worse, I've read that it has a fusible link in it that would blow around 100 Amps, so even with a 136 Amp alternator, the factory alternator cable has to go. I'm one to go all out on battery cables (can never go wrong with too much Amp capacity in a wire), so I converted all of the battery and alternator cables with 1/0 gauge car audio cable (the super fine strands). For positive, I ran one cable from the alternator to the positive terminal on the battery and one from the positive terminal on the battery to the fuse block (I'll install a 250 Amp fuse as soon as I get the necessary bolt). For the negative/ground, I ran one from the block to a frame motor mount bolt, and then from that bolt to the negative terminal on the battery. No single cable is over 2 foot long, and at 2 foot 1/0 has a capacity of something like 600 Amps with 1% drop. (needless to say, I think I'm good going forward).

Result:
Rock solid 13.8 Volts at idle with fans running full out. SUCCESS!

bad_idea

Looks good. I'll have to look into that alternator. Mines a 90, so I'm sure it will be a PITA figuring out the wiring.

Edit: Turns out the Renix uses a GM alternator - CS130. I'll be sourcing one of those. Carry on.

XJlimitedx99

Good stuff man. Back in the day I upgraded the wires to 4 awg (they're even smaller from factory) and the alternator to 136 amp. Always wished I just did the 160 amp.

Batman33165

You did this to your 01 XJ or you have an earlier XJ?

CLSegraves1

My XJ is a 2001.

CLSegraves1

Question:

I've noticed that at idle, the voltage at the battery is 13.6 Volts (13.59-13.61 measured with a volt meter) at idle.
If I crack the throttle to 1000 RPM (or more), it jumps to 13.8 Volts and maintains until I return to idle (voltage returns to 13.6).
It's ROCK SOLID at 13.6 Volts, but I'm curious as to why it would increase to 13.8 Volts with RPM.
It never goes above 13.8 Volts.

It does this whether or not I have load on the system (so it's not because it's short on amperage). Any ideas?

Am I correct in understanding that the PCM adjusts the alternator output based on what it "thinks" the vehicle needs? If so, it is possible to remove the PCM control and instead wire the alternator with a voltage sensing wire to measure direct voltage of the system (like older vehicles)?

CLSegraves1

Pictures from today's commute. 3:13 PM in Arizona (103 degrees outside), Idling in traffic, AC on Full.

Cooling system is just a stock XJ radiator with 3 eBay 10" fans (on the Dirtbound shroud), 180 degree T-stat and distilled water/water wetter (no anti-freeze).

Tsaani97xj

Because the faster the alternator spins the more power it puts out. The regulator keeps it at 13.8. A smaller pulley would up the idle power. I wouldn't worry about it.

Veeb0rg

Which fans did you get off ebay?

CLSegraves1

10" INCH S Blade SLIM ELECTRIC RADIATOR FAN PULLER HIGH POWER MOTOR 1000 CFM

They say they are 1000 CFM but there's no way they put on that much air. I'd say 750 CFM max, but they get the job done just fine. I went crawling around in the desert yesterday afternoon (105 outside) with the AC on full and the temps stabilized at just under 210 on the factory gauge.

99thunder

But the question is how many amps is the 160 giving off at idle?

CLSegraves1

Don't know but it really doesn't matter as it's a good bit more than the stock alternator. Better is better...