My Dilemma...

Hi,

88 XJ Reman 4.0L and AW4 Tranny, DUAL ELECTRIC FANS, open cooling system, High Output Alternator 170Amp, Multi-amp Stereo, Computer, A/V, GPS, etc.

Here's my dilemma:

I have the stock oem electric fan for a 94 and added another electric fan from a sonata (was the thinnest high output I could find at the junkyard) in place of the clutch fan.

All wired into an adjustable temp controller from FLEX-A-LITE. The set-up works GREAT! In addition to the fans coming on automatically I can also manually turn them on with a toggle.

BUT, when I switch my electronic goodies on and/or the AC, lights the Alternator just can't keep the RED TOP OPTIMA charged enough for the FANS turning fast enough to keep the engine cool. I thought about adding a battery isolator and second RED TOP just for the FANS.

SO, I'm debating whether or not to revert back to the oem clutch fan (since that will be one less hungry electric motor sapping the battery) or adding a second battery? What do you think guys?

Thx.

WELL if you're going to be spending the money on another red top why don't you think about an upgrade in the alternator area? Green Meanies are supposed to be top notch High Output alts.

I'm not an electrician but I know just enough to be dangerous....

You have a 170!? amp alternator? If it is in good shape I can't see how it can NOT keep up. Have you considered a problem in your charging circuit?

are you willing to share info on this alternator - model? applications?

Thanks

Hi,

Thx 4 the replies.

According to the Alternator Mfg (I got it from one of these sources can't remember which... JC WHITNEY, QUADRATEC, or PHOENIX GOLD AZ), this is about the biggest output alternator that can fit in the stock area.

They even said that with my given electrical load I was pushing it. The charging circuit is fine I had it cked out by my buds at JEEP (they also installed the Alt for me).

Prior to changing the Alternator to the High Output one I went through TWO oem Alternators that just couldn't keep up with the current demand.

So, unless I add a second Red Top or revert back to the oem Clutch Fan I cannot run all of my electronics, lights, computer, AC simultaneously or the electric fans won't spin fast enough to cool the engine.

btw- If I'm driving then there's a little more current and I can run everything briefly. Probably since the fans aren't coming on as much due to ram air effect.

Any other suggestions greatly appreciated. Thx.

It seems odd how one extra electrical fan would make the electrical system drag behind.

Just think how many lights people put on their rigs with a stock system and don't have any issues.

Maybe you should get your alternator tested?

I'm sorry, I do understand what you are saying but 170 amps is HUGE amounts of power. I guess if you have every single electrical thing on you might come near that current draw...high beams, 4way flashers, wipers, rear defrost, heater fan on high, brake lights on, cigarette lighter, stereo cranked, rad fans on, interior lights, aux driving and fog lights...but I still can't see it unless that sonata fan draws some ridiculous amount of power.

But consider this, the battery is just a storage device for starting the vehicle. When the engine is running, it is the alternator that provides power to your electrical goodies so if your 170 amp alt can't keep up now, adding another battery won't help. What you describe is that the current draw of all your electrics is greater than the 170 amps that the alt can put out. Having another battery would only increase the current until the battery drains, and it will because there is no juice from the alt to recharge it.

Also, there is no free lunch - an alt putting out that kind of amps will be a huge drain on horsepower.

I'm very interested in this problem you are having because I have a taurus fan that is going into my 90 XJ and I have done some preliminary calculations and was going to go with the 136amp alt which seems like it will be plenty. I think stock has about 68 amp alt?

another thing to consider is that one of your fans (or other electrics) has a partial short that is causing excessive current draw.....

My XJ came with a 90 amp alternator.

It depends, I think there was a lower alternator offered.

Police package got a 120.

get rid of the xj and buy a car or suv more fitting to all the extra electrical stuff you have installed or step up and get a greenmeenie alt and dual battery setup to add to what you already have. (run 2 alts)

Shame on you, dzraces. Ban!

Blaine B. said:

Shame on you, dzraces. Ban!

Click to expand...

LOL your calling for my banishment and your not even a paying member :dunce: I offered a opinon and a second option not mentioned by anyone yet of running 2 alts.

Ban!

My two fans together are rated at 50AMP. I have a 130 AMP alternator form a WJ. My alternator supplies enough power to run everything including the AC at idle even with one yellow top. You should check the wiring again. Maybe they are too small. The OEM wires are too small between the alternator and the PDM/battery. Also, try to find which of your equipment is the offending one and repair/replace it;........maybe a wire upgrade to that unit could help.

seems like that alt should be plenty, something is drawing down your power from the alt. A corroded wire will draw more amperage than the device it powers, bad grounds can also give you some issues, before throwing money at this problem, I'd respectfully suggest you take an afternoon chasing down wiring issues, starting with cleaning up and/or replacing the various grounds on your rig. It can't hurt and may head off some other problems in the future.

Hi,

Good suggestions all. Well, after much deliberation I removed the Sonata Fan and reinstalled the oem Clutch Fan.

The mech that removed the original studs on the fan pulley had cut down some bolts to around 1/2 inch and installed them to hold the pulley on unbeknownst (sp?) to me. They'd be too short to hold the oem Clutch Fan.

I found that out after taking everything apart late evening and the nearest store's closed. GRRRRR!!! So, I rummaged thru my junkbox and found a pack of MOPAR studs with two nuts on each except for one that I found a replacement later. I must have bought them awhile back but forgotten I had them.

The studs have different threads on each side and the nuts only fit on one side. I put the side w/o the nuts into the pulley. IS THIS RIGHT? The threads seemed like they weren't catching and when they did I had to use much brute force to tighten them all the way down not to mention I bent several screwdrivers used to hold the pulley from turning.

I then removed the nuts and installed the oem Clutch Fan. I used one nut on each stud. ARE YOU SUPPOSED TO USE A LOCK WASHER TOO OR NOT ON EACH STUD?

More Q's:

1. What is the CFM of the AUX Electric Fan (the one that turns on when you switch on the AC) for a 94?

I have a FLEX-A-LITE ELECTRIC FAN that I might install in place of it if the oem's CFM is less. I don't recall the model # but it's the one in the write-up on CHEROKEE AMERICA. They used it to replace the clutch fan in that article.

Then, I'd have a new AUX Fan and the oem clutch fan. After this, I'll ck the wiring and electronics. Hopefully, I'll have solved my dilemma. Thx.

techno1154 said:

My two fans together are rated at 50AMP. I have a 130 AMP alternator form a WJ. My alternator supplies enough power to run everything including the AC at idle even with one yellow top. You should check the wiring again. Maybe they are too small. The OEM wires are too small between the alternator and the PDM/battery. Also, try to find which of your equipment is the offending one and repair/replace it;........maybe a wire upgrade to that unit could help.

Click to expand...

What's the model # of the YELLOW TOP?

Are you using it with the stock battery tray?

Is the YELLOW TOP better than the RED TOP?

What is a PDM?

Thx.

Yellow top can be drained/recharged many times without damage...

Redtop cannot.

Bluetop is essentially the same as the yellowtop but for marine applications. Maybe it's more resistant to a harmful salt-water environment?

fuzzydog said:

But consider this, the battery is just a storage device for starting the vehicle. When the engine is running, it is the alternator that provides power to your electrical goodies so if your 170 amp alt can't keep up now, adding another battery won't help. What you describe is that the current draw of all your electrics is greater than the 170 amps that the alt can put out. Having another battery would only increase the current until the battery drains, and it will because there is no juice from the alt to recharge it.


another thing to consider is that one of your fans (or other electrics) has a partial short that is causing excessive current draw.....

Click to expand...

both the above points are solid, but i suspect that you problem isn't happening as much when you are driving at highway speeds and pulling more rpm's but when you are idling and your alternator is putting out NOWHERE NEAR 170 amps. this is a common problem on diesel sailboats. you have an engine that never goes over 1500 rpm and a 300 amp altermator the has a pully sized so it needs the engine at 3500 rpm to get the rpms it needs to run full amps.

my advice is to seriously evaluate what your needs are power wise and at which engine rpm's and then resize you alternator pully apropriately.

Digitruck, did you put an amp gauge on your alternator to determine how much current it's actually generating? And, at what RPMs is this alternator supposed to give you 170 amps? Max output is not normally obtained at idle speeds. If you're really interested in supplying sufficient current for all of your electrical goodies, you start by listing each unit and its current draw. Add it all up, and that's the MINIMUM requirement. Then you size the alternator to the minimum plus a little reserve. Also, your regulator plays a very important role in how much current you can force into your battery. A standard automobile regulator will recharge a battery at a very slow rate, no matter how big the alternator.
As far as wiring goes, unless you did a lot of re-wiring, the XJ system is way too small to handle those kind of amps. You should have a "small battery cable" running from the alternator to the battery, and additional feeds to your new, high-draw add-ons.

DIGITRUCK said:

What's the model # of the YELLOW TOP?

Are you using it with the stock battery tray?

Is the YELLOW TOP better than the RED TOP?

What is a PDM?

Thx.

Click to expand...

The red is in the stock battery tray. I made one for the passenger side and is placed where the OEM air box used to be. Any of the two batteries will fit in the OEM battery box.
The red top is 800 CCA (Cold Cranking Amps)
The yellow is 750
PDM is 'Power Distribution Module' .
The PDM holds the fuses and relays and is located next to the OEM battery box. The main or output cable from the alternator is connected to the PDM, in paralell with the battery positive cable. Some of us who replaces the OEM alternator with one of a higher output also replace the main cable between the alternator and the battery with a #4 (4 AWG) cable and the apropriate fuse.
Hope this helps.

xjbubba said:

Digitruck, did you put an amp gauge on your alternator to determine how much current it's actually generating? And, at what RPMs is this alternator supposed to give you 170 amps? Max output is not normally obtained at idle speeds. If you're really interested in supplying sufficient current for all of your electrical goodies, you start by listing each unit and its current draw. Add it all up, and that's the MINIMUM requirement. Then you size the alternator to the minimum plus a little reserve. Also, your regulator plays a very important role in how much current you can force into your battery. A standard automobile regulator will recharge a battery at a very slow rate, no matter how big the alternator.
As far as wiring goes, unless you did a lot of re-wiring, the XJ system is way too small to handle those kind of amps. You should have a "small battery cable" running from the alternator to the battery, and additional feeds to your new, high-draw add-ons.

Click to expand...

Nope, this Amp Guage how does it hook into the circuit to measure Amps? Inline or Induction?

I'm not sure at what RPM's does the Alt put out 170A but the mfg rated it as such and I'm betting that when you're driving is when it puts out that 170A not when it's idling.

Thx.