Alternator Powermaster 8172

So I have Andy’s motorplate and alternator bracket kit and an 8172 it seems to be struggling to keep up with my needs. My Demon has the dual fan setup on it, an electric water and fuel pump and an MSD 6AL. If this one isn’t big enough is there another alternator that is that will fit Andy’s bracket?

That is only a 50 amp alternator according to specs. The 8182 is listed as the same size alt and is 75 amp. Only thing is it is listed as 1 wire but not jumper wire. You can go to this link and check out what they have:

http://www.powermastermotorsports.com/race_alternators.html

You must have something set up wrong. Even a 50 amp alternator can keep up with that stuff on a drag car. If it is a street car then it should also be fine unless you are just sitting in traffic for long periods of time. The fans should shut off as soon as you are moving. If you are running the fans full blast while you're driving down the road then that is your problem. If you have the fans shut off while moving then you have a different issue, maybe a weak battery or poor wiring.

Wiring and battery are all brand new. I guess I need to determine if the 8172 needs a jumper wire or if its a true 1 wire.

Brand new doesn't mean it is done correctly. How are your fans wired? Are you running them all the time even when driving? If the fans aren't on then the current draw is well within the capacity of that alternator. Even if the fans are on all the time at the track the battery should have enough capacity to handle it.

The fans only cycle when the Dakota Digital box and the sending unit agree they need to come one, then it has the option of running itself on low or high as needed. The car is wired correctly. The alternator has one of Crackedback Rob's big wires from it. The alternator doesn't appear to be outputting more than 11.4 volts into the system.

I know it's a odd question, but do you have the alternator case grounded? Sometimes a dedicated ground is needed beyond the chassis ground.

It is attached via an aluminum bracket to an aluminum engine plate bolted to a steel bracket that is welded to the chassis. My old alternator setup with elephant ears didn't have another ground, if it needing a separate ground wire is still believed to be a problem I have no issue adding one. Although it appears based on Powermaster literature that the 8172 needs an exciter wire or the IGN terminal on the engine sent to a keyed 12v source.

You either have a bad alternator or it isn't wired correctly. Shouldn't be too hard to figure out either way. Take it to your local NAPA and they'll tell you if it is working. If it works on the NAPA test bench then you have the car wired wrong.

I'll take it in. So the info is out there the fuel pump, water pump and ignition as well as the fans are all on with the 11.4 volt measurement. Tested at the starter relay with a voltmeter.

Sounds like you just need the exciter wire hooked up

Called PowerMaster they say this isn't enough alternator and they don't make a big enough one for what I'm running.

Turn off the fans and see what your voltage is.

Install a relay switch and go straight to the battery for the fans, Then your switch in the car for the electric fans are just an on/off switch.

X2. With engine running around 1,500 rpm, charging system voltage should be somewhere around 13.5 volts just feeding ignition, fuel pump, water pump. If it is still low, I would start digging deeper into wiring or possible no alternator output. If it only goes low when the fans are on, your wiring is too small or your alternator output is less than fan draw. Try it old school. While the engine is running, touch a screwdriver to the back alternator bearing. If it pulls down the screwdriver, your alternator windings are live. If it doesn't, alternator isn't turning on.

Why would I want that?

I drive it on the street and the last thing I want is to forget to turn the fans on. It is wired the way it is because that's how I want it. I appreciate your suggestion but I'm not changing it.

I also don't believe that's going to solve the alternator output issue I'm having.

You need to manually turn the fans off so you can debug your problem. Turn them off and drive the car and see what the voltage is. You should have 13.5 volts with the fans disconnected. If so then good. If not then you have a charging problem. Once you have that figured out hook up the fans and do the test again.

You can still have them come on with the ignition switch using a relay (wiring 101), The idea is to pull your power from the source not the alternator, using a relay is eliminating running high voltage past the firewall and having the shortest power source to the fans, Maybe a read on basic automotive wiring is in order.

It is high amperage through a switch we are trying to avoid. The Dakota Digital controller probably has a built-in mechanical relay, or mosfet switch.

Do you have that exciter wire hooked up? That is the first step here.

According to their instructions.
A second relay is required for dual fan or two speed fan operation.

There are two relays in my Dakota setup.

Powermaster tech rep said no exciter wire is needed if "I bought it in the last couple years"

The Powermaster is apparently very sensitive to the belt not being tight, it is tighter now and that helped some.

After reading all the posts, my suggestion is to check the voltage with the engine at various RPMs. This is due to pulley ratio.
Around idle (800 rpm) it may only be 12 volts, but checking at 1500 and 2000 rpm should show 13.5-14.4 at the alternator terminal.

Then at the rpm the alternator is putting out 14 volts, check the voltage at other places, battery terminals, MSD or accessory points.

Rattrap,

The amperage doesn't pass through my firewall, I have eliminated all of that wiring, the fans come on with a 12v keyed relay and the power for all the extra components in my car are fed from two new fuse blocks that are independent of the factory fuse block.

I have a Toyota forklift 55A alternator on the RR along with a CSR electric waterpump (POS), an electric fuel pump, dual electric fans from a Dodge intrepid, and a MSD 6AL and HVC coil. Purchase an amp clamp and measure the current at the alternator (big wire) with the alternator full-fielded, then measure the current on the power or ground leads to each component and add them up. My load was nearly 50 amps, and over 55A with lights on. Alternator was producing a maximum of 58A. Even if the load was under 55A the alternator would be at or near full-field just to keep up. At full-field it's just a matter of time before the alternator overheats. Want a real diagnosis instead of a lot of guesses? Get the amp-clamp and measure the alternator output and then measure all the loads and do the math. I suspect you'll find you need a higher capacity alternator or fewer electrical loads.

If you think it's the wiring or grounding then do voltage drop testing. First battery positive to alternator power lead, then battery negative to alternator case, with the the loads turned on (duh). Anything over .5V (half a volt) on any one lead and it's too much especially for new wiring. Next voltage drop from alternator power output to positive lead into each load (fan, fuel pump, waterpump etc) at the load, then alternator case to ground lead to each individual load. Again, anything greater half a volt is too much and requires a wiring repair.

FWIW, my 55A alternator is too small...and for sale just like the fuel pump and waterpump.

I had a 60amp Denso on my Duster, it had a mechanical water pump and fan, electric fuel pump with a return line, worked great, always charged around 14 volts, regular automotive battery.

Now on my 70 Challenger I had a TuffStuff 100amp alternator and an Optima red top battery, I had nothing but battery problems every day, I run an electric water pump, electric fans, and electric fuel pump.
I switched to a regular Walmart battery and life was much better but not perfect. I then bought a 165 Amp Powermaster alternator and now I never charge my battery. It may be way overkill but now all I do is hop in my car and enjoy it every sunny day.

WHAT PN Powermaster replaces that Denso? I think I have a 60amp Denso, from a Toyota 4 runner?? Cant remember its been a long time since I bought it at the parts store LOL

I agree that the only way to solve these problems is with data. Most people don't have a amp clamp but they are fairly inexpensive these days. I've seen them as cheap as $20 but somewhere in the $50 range is probably more common. It is just like anything else, if you don't have the right tool then you can't do the job. I picked up an amp clamp meter last year when I was having some starting problems and I used it to check the current flow all around the car. On my car a 60 amp Denso is more than adequate even with fuel injection and an electric fuel pump and all the other stuff.

A 60 amp Denso alternator is more than enough for most race cars. You have to remember how many systems on the late model cars use and our cars only use 3-5 loads on the system. Say you have a 99 Toyota Camry with a 60 amp Denso alternator on it and it keeps up with a/c fans,blower motor,wipers,radio,lights,etc... They still charge 13.4 with everything on at idle and charge 14.5 just running a fuel pump and a few other basic items. As long as everything is wired correctly with large enough wire the basic 60 amp unit will keep your battery charged for years.
Gus