Chevy 350 engine question 3 wire alternator? I have a 100 Amp Powermaster alternator. My car is setup with dual fans from a Ford Focus. One fan is on all the time, the other is set to come on when the A/C is on (I am going to change that to a temperature controled setup). Both fans run thru seperate relays. Today I noticed that when the second fan comes on the Ammeter goes to a 15 amp discharge. Without it on the gauge is normal. No change when the headlights are on. Checked the voltage at the battery. One fan on it was 13.6, when the second fan came on the voltage dropped to 12.5. Which says to me no charge. I also noticed the alternator was whinning with a beraing like noise. Verified it to be the alternator by taking the belt off, no noise with the belt off. Also with the car in vent mode and blower motor running no effect on the Ammeter. What do you guys think?
- Thread starter chevt73
- Start date
Sounds like the motor on the second fan is putting too much load on the alternator. If you look on the Flex-a-lite web site at their fans some of them can draw upwards of 10 amps all the way to nearly 30 amps. If you've got a typical automotive alternator it's probably only putting out 35 to 40 amps. Most blower fans don't draw that many amps so you wouldn't see a big difference with just one cooling fan running, the heater blower and any other small accessories. Even headlights don't typically draw a huge amount in relation to a cooling fan. So with both fans running, along with any other normal draw, it's probably close to maxing out the alternators output. That would account for the low voltage with everything running.
The first thing I'd do would be to take the alternator and have it checked out. If it's not rated at at least 40 amps I'd check into one with a higher output. Too the alternator may not be completely dead but the brushes may be worn to the point that the output is being reduced. I had a truck years ago that did something similar when the brushes got down close to being gone and the resulting spring tension on them was severaly low. The lights would dim, the wipers were slow, etc right up until the end when it quit putting out completely, the battery died, and everything died...while I was out of town in a heavy rain...
The first thing I'd do would be to take the alternator and have it checked out. If it's not rated at at least 40 amps I'd check into one with a higher output. Too the alternator may not be completely dead but the brushes may be worn to the point that the output is being reduced. I had a truck years ago that did something similar when the brushes got down close to being gone and the resulting spring tension on them was severaly low. The lights would dim, the wipers were slow, etc right up until the end when it quit putting out completely, the battery died, and everything died...while I was out of town in a heavy rain...
Charlie Biler x
Member
If you do not have 14.3 volts when the alternator is running, the battery is not charging. At 13.6 volts a 12 volt battery is at rest. At 12.0 volts a battery is dead.
Unhook your fans and read the voltage at the battery, with the engine running. If you do not have 14.3 volts, fix the alternator. Any decent 10-SI Delco alternator will put out 100 amps. Ratings on those old analog beasties were determined by how hot they wanted to let them get. At 32 amps the alternator is cool to the touch. At 100 amps she needs a fan to keep the trio and rectifier block from melting down.
My guess is your regulator is one of those two buck auto store specials or the diodes are the ones rated for fifty imaginary amps at the south pole on winter. This is not a slight on you. It is impossible to look at components and gage quality. I ran a rebuild shop for years and people bitched about my prices. They could buy a 10-SI regulator for five bucks at an auto parts store. My regulators cost me eleven bucks before I touched them. I could buy two dollar regulators, but I did not need the headaches that came with them. Alternators today are mainly a race to the bottom because everyone looks at price. The new digital CS130 alternators are pure scrap when new.
Just remember that heat drops output of an alternator because the regulator is temperature compensated. Cheezeball diodes make heat. Heat also lowers the trio efficiency and burns the insulation on the stator. Paper insulated stators cook really fast. Make sure you run a varnished stator. Varnish insulates better and stops water decay on the laminations. To kill an alternator, just hose it down and the paper insulators on the stator laminations become conductive mush.
Happy motoring.
Charlie
Unhook your fans and read the voltage at the battery, with the engine running. If you do not have 14.3 volts, fix the alternator. Any decent 10-SI Delco alternator will put out 100 amps. Ratings on those old analog beasties were determined by how hot they wanted to let them get. At 32 amps the alternator is cool to the touch. At 100 amps she needs a fan to keep the trio and rectifier block from melting down.
My guess is your regulator is one of those two buck auto store specials or the diodes are the ones rated for fifty imaginary amps at the south pole on winter. This is not a slight on you. It is impossible to look at components and gage quality. I ran a rebuild shop for years and people bitched about my prices. They could buy a 10-SI regulator for five bucks at an auto parts store. My regulators cost me eleven bucks before I touched them. I could buy two dollar regulators, but I did not need the headaches that came with them. Alternators today are mainly a race to the bottom because everyone looks at price. The new digital CS130 alternators are pure scrap when new.
Just remember that heat drops output of an alternator because the regulator is temperature compensated. Cheezeball diodes make heat. Heat also lowers the trio efficiency and burns the insulation on the stator. Paper insulated stators cook really fast. Make sure you run a varnished stator. Varnish insulates better and stops water decay on the laminations. To kill an alternator, just hose it down and the paper insulators on the stator laminations become conductive mush.
Happy motoring.
Charlie
steve n carol
Member
"..... all died, out of town, in a heavy rain....." There's a song in that somewhere!
couldn't resist..
charlie you and I need to talk!!! I am accumilating parts to refine my self made electric vehicle. I need your help and advice on an alternator set up to made it a so to speak parcel hybrid. Need to put out in the range of 80 volts bill bills [email protected]
Powermaster claims that their alternators do not work well when spinning below 2400 RPM. A Powermaster 100 amp unit is usually a Delco 12SI and it puts out less power at low RPMs, not more then a less-amp alternator. Usually has to spin at 1600 RPM to make any power. If you've got an underdrive pulley that makes a engine-to-alterator drive ratio of 2-to-1, the engine has to be spinning at 800 RPM minimum to do anything. If you need 30 amps has to spin faster. To make the 100 amps it's rated at, it has to spin at 6000 RPM.
The newer Delco CS type alternators make more power at lower RPMs then the SI series.
How fast is the alterator spinning when you see the discharge? Most gas Chevy's have an engine-to-alternator pulley ratio of 2.5 to 1. So, it ought to work even with the engine idling at 600 RPM unless you've got a larger alternator pulley.
Also, what kind of amp gauge are using? Direct read, or the shunt-wire versions that some GMs use?
The newer Delco CS type alternators make more power at lower RPMs then the SI series.
How fast is the alterator spinning when you see the discharge? Most gas Chevy's have an engine-to-alternator pulley ratio of 2.5 to 1. So, it ought to work even with the engine idling at 600 RPM unless you've got a larger alternator pulley.
Also, what kind of amp gauge are using? Direct read, or the shunt-wire versions that some GMs use?
Hobo,NC
Well-known Member
- Location
- Sanford, NC
Sounds like your amp meter is useless (as most elcheapo automotive/tractor amp meters are) you can for the most part believe the voltmeter...
A alt will cry when you load the chit out of it,,, a alt will cry when one phase is not working, if a phase is down for the count the other 2 phases are operating at max output and will cry...
Make sure the belt is tight,,, make sure the pulley is tight to the alt shaft,,, you need to use a inductive amp clamp tween the alt and bat to verify the alt will produce max amperage,,, if it can not produce then the alt needs to come off and checked...
A lab scope can also be used to look at the alt wave form ,,,everyone has a lab scope ,graphing meter and a amp clap rite,,, the alt can B easily taken apart and checked,,, also you are gonna need at least a alt that will output 100 amps,,, the CS130 mite B a good upgrade if you are going to demand that much output,,, the 130 will pump out more at a lower RPM...
I would drop the dual fan and go with a ford t-bird/Taurus style of the 90 to 1995 vintage,,, cheap from a junk yard and EZ to mount,,, next you can by the temp controls to operate the fan for around $50,,, you will need to plumb into the top rad hose are at are near the thermostat,,, also you can wire a relay in to command the fan on with the AC on,,, I would have to think about how you would shut the fan down once you got above 30MPH,,, the fan is not needed then and with the demand you will overwork the alt are you will need a alt that will Easley out put 50/60 amps continuously,,, sure the 130 is more probamatice,,, it does twitce the work over a standard 10SI,,, even when you soop up a 10SI its designed to cool a 60 amp alt not a 100 amp alt (well it something to think about)
Note none of these test are valid unless the bat is fully charged and in good condition,,, folks that know their chit can use a voltmeter to determine if the alts working good but a elcheapo amp meter is not that much help,,, even a alt that's going out can produce 66% of the total amperage the alt can produce,,, so even if yer 100 amp alt puts out 66 amps it can be bad,,, but the volt meter would read low so for most would be the tip sum'n is not right,,, folks that believe and praise a elcheapo amp meter over a volt meter are showing they don't know what they are talking about (refer back to 66%) So yer amp meter reading are know good at this point (we don't know the quality of the amp meter are the range are the actual load on the system) for now you are going to have to depend on the voltmeter,,, the cry and voltage reading with no other tools would have me look'n into the alt after I confirmed the bat and belt were in good condition (do you have under drive pulleys on yer chebby?)
For whatever reason the second fan is overloading your electrical system.
Clue 1: 3.6 volts running. Alternator is barely maintaining battery level.
Clue 2: 12.6 volts when loaded with second fan. Now the alternator can't keep up the load hence the negative ammeter reading. The battery is discharging through the load.
My first thought would be have the alternator tested under it's specified load.
Possibly frog the fan connection and see if the problem follows the second fan.
Thanks for everyone's input. Pulled the alternator today. Had it tested at both a Kragen and Auto Zone store. Both test showed it to be bad.
Also found out it was not a Powermaster but made by TuffStuff.
So I have a new 140 amp on order. Hopefully that will fix the issue.
Also found out it was not a Powermaster but made by TuffStuff.
So I have a new 140 amp on order. Hopefully that will fix the issue.
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