Hi Folks-
I just installed the following:
- Taurus electric fan
- 100A relay with 50A circuit breaker (fan kicks on with 90 amps but draws 30)
- Powermaster 100A alternator model 8002

I have the following:
- MSD ignition
- Voltage gauge in car

When I turn the car on and give it a little gas, the volts shoot to 14.4 immediately and hold there. Lights, brakes, etc small dip in volts and rebounds. I turn the fan on, and it drops to 11 volts and does not recover. The alternator is grounded to the frame as well as the engine, the fan receives its power through a 10 AWG wire to the junction block near the alternator, and it is grounded to the body. The car battery is also grounded to the frame.

Can anyone point me in the right direction? I don't want to take the car out and have the battery die or have it over heat on me.

THANK YOU!

Grab a volt meter and measure the voltage at the alternator. If dip to 11 volts then your alternator is either not delivering the 100 amps or the fan belt is slipping. You may double the fan belt or use a serpentine belt so it won't slip. If does not drop then run a heavyer gauge wire between the alternator and junction terminal.

Any easy way to check for belt slippage? I am already using 10 AWG between the alternator and the block, which is rated for 100 amps.

10 gauge with not handle 100 amps you need least 8 gauge or lower.

Thanks, so do you think my 10 AWG is just heating up and resisting the increased current?

It's the other way around. As the wire heats up the resistance will increase. Therefore the voltage across the wire will drop. Just use a volt meter and measure the voltage at the terminal. If that voltage does not drop then it's the wire. If the voltage drops then you got other issues. You may have to test the alternator.

Yeah, it is heating up and resisting more. I am going to test the alternator as well, it's a brand new powermaster unit.

Alternator passed testing. Should I run a larger wire directly to the battery?

:yes:

And maintain a wire to the distribution block? Thanks again!

One more bit of info... my battery is in the trunk.

Run a heavy wire from the alt to battery and then run a heavy wire from the battery to the the car horn terminal from there is goes to the fuse panel.

Will do, 8 AWG all the way. Thanks for your help!

Run the heavy wire from the alt the starter terminal and junction terminal.

Will do, 8 AWG all the way. Thanks for your help!
:yes: BTW: Alt will not produce the voltage when you turn on the fan if the engine is running at idle.

At night with the headlight working it's even worst at idle. My chevelle does that now, and I do not have an electric fan. It drops to about 11 volts idle and when I bring the RPM up, the voltage will jump to 14 Volts.

One more bit of info... my battery is in the trunk.

Are you using the 3 wire hookup or single wire to the alternator? Single wire hookups are notorious for low current output at idle. Also since your battery is mounted in the trunk, you really need BIG wiring back there, more like #4 or even #2 AWG. During cranking, you'll have a significant voltage drop from battery to starter if you run 8 or 10 gauge wire. It's a good idea to not depend on the frame for your battery ground. Run a separate HEAVY ground cable from the block to the battery.

#2 AWG for battery ground to frame and from pos terminal to starter. This alternator is rated at 70 amps at idle speed and tested there. I am going to increase the wire size for the alternator charging wire and also re-wire brush my ground wires and go from there. I will also add a ground wire as you are suggesting. Thanks!

I forgot, I use 3 wire alt. When I release the pedal and the RPM drop to idle the voltage drop to about 12 volts. That's normal for my Chevelle. It only happen to me at night. I'm only using a 50 amp alt. not to mention I'm running halogen headlights. They pull a lot of current.
MD, it is a little different.

Any easy way to check for belt slippage? I am already using 10 AWG between the alternator and the block, which is rated for 100 amps.

As a rule of thumb if you can turn the alternator by hand by manually turning the fan then your alternator belt is too loose. If you cannot then its not likely too loose regardless of what amp rating alternator you have.

Having said that, I have to admit that I can REALLY put some torque on something like that. I'm big enough. That makes it a valid test for me. You little guys may not be able to perform the same test. Not that little guys aren't strong! :-)

I can turn the alternator pretty easily, the water pump spins and the crank pulley belt to the ps pump slips and does not spin.

One last question for now: Could all of this be caused by a bad ground for the fan?

You could have a bad ground connection from the block to the chassis frame. I seen that happen. Don't forget, the engine and tranny sits on rubber mount.

I've added 8 AWG wiring from the alternator to the junction block as well as 2 grounds from the block to the frame. At this point, I have rewired everything. I am going to get a new battery and redo the battery cables, and, if that doesn't work, I have ordered a new shroud, 7 blade fan, and hd thermostatic clutch. At least I didn't shell out much for this fan...

Ok... all those upgrades didn't work. One more try, new battery tomorrow. Already ordered the mechanical fan stuff. I bet this electric fan is on its way out.

Thursday morning update: Battery failed the load test! New battery in the back of the subaru, I'll see what it does this evening.

Car runs great -- fan hits, volts come back up to 13.5. I idled her for 20 mins, temps stayed steady with fan on!

Glad it is fixed, Congrats to you:hurray:

Me too, I appreciate all the help! Car runs reallll good!