My powermaster alt can't keep up with my fan

ng8264723 · #1 (**permalink**) 10-15-2010, 09:20 PM

I think it should but the voltage drops when I have the fan and lights on. I'm running a powermaster and a motorcraft regulator

Excaliber · #2 (**permalink**) 10-15-2010, 09:48 PM

Drops to what voltage at what rpm? If your talking about idle rpm and the lights "dim" when the fan(s) are on, that could be considered normal.

bobcowan · #3 (**permalink**) 10-15-2010, 10:07 PM

Yes, it should. I use a rebuilt 70A Mustang unit with external voltage regulater. I use the largest Spal fan I could fit in there. Even with the brights on, I don't get a voltage drop. Except at idle. Then you'll see the voltmeter drops just a smidgen. But once the rpm's are back to 1,000+, there's no issue.

Tommy · #4 (**permalink**) 10-16-2010, 05:38 AM

Insufficient information. On the Summit Racing website, there are ten pages of Powermaster alternators with a wide range of output (amps) values. You need to know the output of your alternator and the draw (amps) of all you electrcial accessories to better understand what is happening. If the total draw exceeds your idle alternator output, you will get the symptom you describe. BTW, if the dropped voltage is above 13 volts, it shouldn't hurt anything.

DAVID GAGNARD · #5 (**permalink**) 10-16-2010, 06:47 AM

Quote:

Originally Posted by ng8264723

I think it should but the voltage drops when I have the fan and lights on. I'm running a powermaster and a motorcraft regulator

Are you using underdrive pulleys??????? if so, at idle, you'll see a voltage drop with any alternator.........

David

kobrabytes · #6 (**permalink**) 10-23-2010, 08:11 PM

Quote:

Originally Posted by ng8264723

I think it should but the voltage drops when I have the fan and lights on. I'm running a powermaster and a motorcraft regulator

Does your ignition key get hot when you have everything running?

Excaliber · #7 (**permalink**) 10-23-2010, 08:20 PM

You know the big reason alternators are superior to generators is that they put out more amperage, and in turn a higher voltage, at low rpm. A generator can make just as much power, but it needs to be big, heavy and turn at a higher rpm to do so.

That said, even alternators need at least a minimum rpm to begin producing decent power and it's a rare occasion when even an alternator will be putting out 100% capacity even at high rpm.

At idle rpm lower than a 1,000 with a "heavy load" like light and fan(s) it's normal for an alternator to not put out enough amps/volts to meet load demand.

RICK LAKE · #8 (**permalink**) 10-24-2010, 07:52 AM

NG8264723 Chris You are leaving out a couple off other loads on the system possibly. Does the car have electric fuel pump??? 6-10 amps. MSD ignition system??? 4-12 amps. Your cooling fan 8-20 amps. Lights 2-10 amps. If you are running a smaller bottom pulley than 5" the system is under drivin. The Alt is not spinning fast enought to power all these curcuits without draining the battery at idle. Size of battery also comes into this draining also and health of battery. CCA I like are in the 800-1000 cca. This gives the systems alot longer time to kill the battery and have the car not start. If running a MSD system, when the battery gets down to 10.2-10.4 volts it will not have enough voltage for the ignition to start the car.
The other issue could be the output on the Alt is not what is said to be on the case. Have to remember that the rating is for MAX ampage, but it can't run this way all the time. If the amp rating on the Alt is 70, it may only maintain a 62-64 amp max without burning up the alt. At idle you may only have a 30-35 amp output and this is not enough. The battery is suppling the extra amps for the car to be running at low rpoms. I have had the problems you are going through. You might want to have the battery tested for CCA and health of it. Go to a good place for a battery check not Pepboys, autozone or Sears. They all have questionable machines for testing and failing batterys. See if there is a higher CCA battery for the car that is the same size as what you have now. I run more electrical than a 70 Alt can handle with fuel pumps (2) fans coolant (3) ignition system, FI system. and Blowers (3). I also have an under driven pulley on the bottom of the motor. Have gone to a 100amp PAPreformance setup and a Voltage meter for the electrical system. I wouldn't recomemend running a higher alt rated than 70 with an amp meter in the car. At this time all volt meters are different color and don't match the original gauges of SW or Smith in the car. If the color bothers you, remove the gauge face and paint it black. You will need to rehook the wiring from the gauge. The problem is cooking the insolators on the gauge and smoking the whole dash wiring harness. Talk to Kirkham about changing to a larger charging system. Rick L.

ng8264723 · #9 (**permalink**) 10-24-2010, 11:58 AM

I'm running the powermaster alt that the kirkham's recommended. It seemed to run well yestreday. When It's running with everything turned on (fan fuel pump lights it falls to about 13-14 volts at a low idle. When you drive it comes up. I have an alum lower pulley but I'm not sure if it's underdrive. I will have to measure it. The car is all stock (kirkham) bat/elec/volt meter. I wonder if I can buy a smaller alt pulley? I would rather change that than the main pulley. It also turns over real slow after it warms up. I guess I need a started heater shield. With the headers so far from the started I wouldn't think it would get heat soaked

chris

greg schroeder · #10 (**permalink**) 10-24-2010, 07:36 PM

Maybe you have a wiring issue.

trularin · #11 (**permalink**) 10-25-2010, 08:00 AM

Back to 1000+?

I idle at 1200.

In stop and go, the alternator will be challenged, but you should be okay driving.

rodneym · #12 (**permalink**) 10-25-2010, 11:09 AM

ng8264723,
Again, check wiring for loose connections. I also had a recent issue with my Kirkham/battery/alternator/dimming. I found the battery kill switch cables to be VERY loose, even after being checked on delivery of the roller and when complete. Those BB's are evil

I think that when my system needed the help from the battery, and charging for that matter, it simply wasn't getting a good connection.
rodneym

lnfletcher · #13 (**permalink**) 10-25-2010, 12:14 PM

13-14 volts at idle is not a problem.
If your battery is running down, I agree with the above, you have a wiring or battery issue.

KSW64 · #14 (**permalink**) 10-25-2010, 07:42 PM

I had the same issue back a few months ago. Start with the simple things like a worn belt. If you have v-groove belt and it has slipped at all, even tighten it will not help the charging problem. Feel the sides of the belt, if there is a ridge near the top, change it. It take about 6-9HP turn a alt at max output. Before you dig into too deep to your pocket book, try the simple things first.

KEN

Ronbo · #15 (**permalink**) 10-27-2010, 03:24 PM

Get one of these and stop guessing:

http://cgi.ebay.com/ebaymotors/KD-To...motiveQ5fTools

If you don't mind spending a little more the Hoyt indicators are built better. (You can had these off to your grandkids when you done using them.)

A voltmeter is almost useless in diagnosing charging systems.

PANAVIA · #16 (**permalink**) 10-29-2010, 01:57 AM

Also if you have a large pulley on the alternator it will reduce current at idle. -- but i agree with others, we need more info.

IMHO, you should be using an alt with 70+Amps capability ( pref 95-130 ) a battery that can store 600-700CCA's and proper grounding , wiring and routing throughout.

--Steve

lnfletcher · #17 (**permalink**) 10-29-2010, 06:38 AM

I guess I confused why ng thinks it's an alternator problem.
13-14 volts at idle is fine, and in most cases better than fine. The new ford alt don't even charge at idle on their new vehicles to improve on fuel milage.
Slow starting after warm-up most likely is a starter or timing issue.

Excaliber · #18 (**permalink**) 10-29-2010, 07:59 AM

70 amp alternator should be plenty. It's unlikely he has enough load to warrant anything bigger, that would be true for most of us in fact.

Let's say your running a 100 or even a 200 amp alt!! So what? If idle speed is low when your running some accesories, it still won't put out enough amps/volts for the load.