Alternator Cooling

Muad'Dib

Muad'Dib

NAXJA Forum User
Location
Bend, Oregon
Ive been having some problems with my alternator in the 90+ degree weather, and i am pretty sure that its heat related.

Im wondering if anyone has added additional cooling to the alternator in our Jeeps? I know some vehicles come from the factory with some type of cooling device for the alternators in them. Usually a molded tube of some sort to direct outside air to the back of the alternator so the alternator's centrifugal fan can pull this air from the back out the front.

One idea / example would be from a BMW. Some have a cover that goes over the back of the alternator that hooks to a 3" (approx) pipe. I dont see why we couldnt take this part, and hook some pipe up to it and run it to say the fender, a hood vent or somewhere similiar to get outside air. Even under the vehicle would work. Hell... you could even add a DC fan to the end of the duct in the cab to really get the air moving around it...

Here is an example of the BMW: (dirty example... some sort of screen would work well here)





Comments , Suggestions? All are welcome. Thanks very much for your time.
 
Summer temps also cause other loads to increase - electric fans, a/c and blower, lower output from the battery, higher voltage drop, reduced voltage available. With higher loads, the main junction simply has less voltage available - and lower voltage has a exponential loss in efficiency.

Voltage drops can run as much as 3 volts at the headlight switch alone. Old, corroded, undersized cables - especially the alt feed and the connection to the main power junction - will kill performance.

Don't blame the heat alone. It may be bringing the system to it's limit because of it's reduced capacity.
 
tirod is right on. whats going to power the fan? I'm assuming the alternator which would just add more load. try upgrading cable especially if the alternator is putting out more then the stock 90a. and also maybe a better battery so the alternator doesn't have to work so hard to charge it.
 
Under the same conditions in the mornings when the outside air temperature is approx 65-70, the alternator runs and performs just fine. None of these voltage drop problems. The AC is on, taurus fan on low, and ignition etc. Same load and conditions in the evening. I dont turn the AC up, nor do i change the fan speed. I leave them as they were in the mornings. The only change is that the outside temperature is approx 90 degrees. The voltage drops low enough to cause the blinkers to slow down while blinking at a stop light / sign @ idle. If i feather the throttle to bring the RPMS up to approx 1000 then the voltage increases and the blinker (as an easy to follow example) starts to blink normally.
 
I'll agree with you that the cooling would be nothing but beneficial, but have you tried asking San Jose generator for their advice? I'm assuming that since it's from them that you have upgraded slightly? If so, I would think that you would definately be creating more heat. I have never heard of anything like this before, but I will start brainstorming for ideas.
 
Muad'Dib said:
Under the same conditions in the mornings when the outside air temperature is approx 65-70, the alternator runs and performs just fine. None of these voltage drop problems. The AC is on, taurus fan on low, and ignition etc. Same load and conditions in the evening. I dont turn the AC up, nor do i change the fan speed. I leave them as they were in the mornings. The only change is that the outside temperature is approx 90 degrees. The voltage drops low enough to cause the blinkers to slow down while blinking at a stop light / sign @ idle. If i feather the throttle to bring the RPMS up to approx 1000 then the voltage increases and the blinker (as an easy to follow example) starts to blink normally.
Click to expand...

I had Similar Issues with my XJ. I was Going to Purchase a New Alternator with a New Battery. I Decided to Purchase the Highest Cold Crank Amperage Battery I could Find. It also had to be Deep Cycling. I Did Not get an Optima Because of the Problems with them over the Last few Years.

After Cleaning the Battery Clamps and Installing the Battery, everything Started Working Fine and the Alternator Tested Good and hasn't Given me Less Than a 13 to 14V on the Gauge in Mornings, during 95+ Daytime, or the Evenings and I am in Sunny, HOT, Florida.

Just my .02
 
My clamps and posts are super clean... The battery is a Exide Orbital Select. Only a few years old.. and other wise works great. Are you saying you think its a battery problem? I didnt think heat could effect batteries in that way.

I have yet to call Rod at San Jose Generator.. been very busy at work answering phones... its hard to make a call myself when at anytime i could get another call that i absoloutly have to answer.. lol
 
Last edited:
whitexj98 said:
Anything is possible I would start with load testing the battery, make sure its working properly then test the voltage drop on your battery cables.
Click to expand...

Ditto. Have your charging/starting systems fully checked. Including correct idle RPM.
The alt on the I6 is mounted low on the engine and would tend to get cooler air anyway, Most alt with piped in air are generally mounted high on the engine and well out of the fans air stream.
IF you have an I6 that is, Sorry so few of the Vs and 4 bannger around here I forget about them.
 
The cables are brand new from Jon (5-90) and the battery has never given me any issues. Always cranks over very easily.. even when its extremly hot out. Only when running and hot out does the voltage drop... To me all signs point to something with the alternator. But ill have the battery tested for shits and giggles.

As far as air flow from the bottom of the vehicle.. that may be another issue entirely. I made a custom "splash shield" under the alternator out of 16 gauge sheet metal to help prevent any water splashing onto it. It attaches to the frame right below the alternator. I could see this preventing some airflow... but not more than the factory plastic air splash guard thingy (that has detorioted and has been removed from my jeep) i would think.....

Yes it is a I6.
 
In the Hot Weather here, I go through a New Battery every 3 to 4 Years. I only Buy High End New Batteries that are supposed to Last 8 Years and have Free Replacement Up to 3 Years. They seem to Know when the Free Replacement Period is Up and Give Out Shortly After that.

I would take your XJ to just about any Parts Store or Auto Shop and have the Battery and the Alternator Tested. At Part Stores they do it for Free. You would have a Better Idea for Making a Decision in what to do. IMHO
 
Have you ever bought a bad part before? I have, and it sounds like u got a bad alt. Its a brand new "should be better than stock" part and your having problems with it overheating. I would call and have a replacment shiped. If only 1 thing in the equashion changed and it no longer works then start with what was changed.
 
I want some of that cool weather,we see 110+ all the time here and Ive never had any issues with alt's or batteries.
 
Im still investigating this issue. Im starting to think its not an actual charging problem, but a motor or clutch problem. When the temps start to rise outside, the compressor clutch or OEM electric fan is trying to pull too much current.

Looking at wiring diagrams, it appears that both the AC clutch and OEM fan run in the same circuit. Im thinking of powering the AC Clutch off of the battery to see if that helps at all (through another relay of course)..

I tried disconnecting them one at a time to see if the voltage would increase while this problem was occuring.. but the voltage loss would only increase after both things were disconnected. The only other load besides the radio was the ignition and blower.

What baffles me is that the problem is only present when it gets hotter outside. Im really still scratching my head about this. I would hate to call Rod and get another alt just to find out that it wasnt the problem.

Unless its some kind of belt slip that i just dont hear. When gatorbacks slip do they make a normal belt slip squeeling noise?
 
I agree that the hotter it is the less efficient the alt. will be, but having electrical issues like you are explaining is different. You're getting significant drain from something. I would check your e-fan, possibly your A/C compressor. I had a similar issue except it was constant drain even when switched off, and it turned out to be a bad light bulb socket. (Talk about insane to trace.)
 
Muad'Dib said:
Unless its some kind of belt slip that i just dont hear. When gatorbacks slip do they make a normal belt slip squeeling noise?
Click to expand...
Like a greased pig! I tend to run my belt on the loose side to try and prevent premature bearing wear on everything.This time of year(AC on) always lets me know if the belt is even slightly loose.
 
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