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Old 06-17-2018, 10:35 AM
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Question Alternator Issue

Hi I am having problems with my charging system. I have a GM 100 amp 1 wire alternator. Wire harness is a kwik wire kit . On start up it charges at 14 volts when everything warms up after a while the voltage drops to 12 volts.when everything is cool voltage is back up. I am not running any heavy current draws only ignition ( GM HEI ) Electric cooling fan Derale, gauge cluster VDO ,brake lights and radio . The alternator is grounded to the block. I have the battery in the trunk and grounded to the frame. Positive cable goes directly to starter where it connects to alternator wire. the pulley on the alt is aluminum and has straight blades. Could the blades being straight cause the alt to overheat by not moving enough air ? Any suggestions on how to solve this issue will be greatly appreciated.


Thanks
Joe

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Old 06-17-2018, 11:59 PM
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I've got the same alternator with the same problem, haven't done anything about it yet, I suspect either it doesn't put out it's rated power or there is most likely a diode with a temp related problem. In cold winter weather it's just fine even with the engine coolant temp up to 195, but as summer comes on it starts out just fine but once the engine gets to 195 it craps out. The hotter the weather the sooner it stops producing power. It will hold 12 volts with the engine turning 2000 RPM but as soon as I hit city stop and go traffic and the cooling fans come on the voltage drops under 12. So I think I'll be shopping for a replacement before too long.

Bogie
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Old 06-18-2018, 02:12 AM
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Sometimes guys use too light a gauge feed wire I've always used a 6 gauge battery cable from the alternator to the positive battery terminal and never had issues even with A/C,electric fan and electric fuel pump, check out this article: https://www.tuffstuffperformance.com...structions.pdf
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Old 06-18-2018, 06:20 AM
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Quote:
Originally Posted by BogiesAnnex1 View Post
It will hold 12 volts with the engine turning 2000 RPM but as soon as I hit city stop and go traffic and the cooling fans come on the voltage drops under 12. So I think I'll be shopping for a replacement before too long.

Bogie

That is exactly what the problem is with the one wire set up. I say it a thousand times. One wire is for lawn mowers, tractors and gas powered welder type of operational conditions.


It is easily seen when a car is using the one wire deal. When looking at a line of cars stopped, the car with the dim & yellow head lights is the 1 wire set up. Three wire has the same intensity no matter what the RPM.

I not going to bother explaining the why, cause it has been over and over and over.

You will never have the problem with the 3 wire set up....... you're certainly free to ignore the advise.

pep
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Old 06-18-2018, 06:42 AM
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I have had a one wire alternator on this rig for 20 years with no problems.
head lights, plow lights, amber flashing, beacon light, heater and radio
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Old 06-18-2018, 01:04 PM
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By adding a simple diode to your one wire alternator it will excite early and full charge at low RPM's.
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Old 06-18-2018, 03:26 PM
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Please explain how "adding a simple diode to your one wire alternator it will excite early and full charge at low RPM's"


Very curious as how that would happen.
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Old 06-19-2018, 11:32 AM
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Quote:
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Please explain how "adding a simple diode to your one wire alternator it will excite early and full charge at low RPM's"


Very curious as how that would happen.
I was having an alternator tested and he made the jumper up for me ask them for details here: Contact Us - GEN-STAR ELECTRIC This shows output at idle because of the low mounting of the alternator I could not get a shot of the wire & diode which converts the 1 wire to a "2 wire"
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Old 06-19-2018, 12:09 PM
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Guess we are digging up "old bones" again. https://www.hotrodders.com/forum/one-...or-272721.html
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Old 06-19-2018, 03:12 PM
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I thought it was something new.....

You can make just about any three wire into a one wire by hooking in a jumper wire (I've never had to use a diode). In a true one wire this is done internally.

Once a one wire receives enough output from the charge lug to excite the field it will start putting out juice and to my knowledge will continue to produce juice until the alt stops spinning. The difference is...… you need higher RPMs initially to get the alt to start producing juice, once it starts producing it works about the same as a three wire.


IMO the drawback is...…. the sense wire is taking the reading from the charge lug, which isn't the ideal place to get a sense of the demand/draw on the electrical system. The three wire OEM setup allows the sense wire gets it's reading further down the line and a truer demand/draw on the electrical system.

Both work just fine.
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Old 06-20-2018, 06:16 AM
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Think of the exciter wire as the pressure regulator on a compressor. It's job is to recover the air that has been used, before it is all gone. That's the best analogy, and describes what's happening. In spite of what some think the car runs off the battery, not the alt.

Also tells you why a car with one wire willie, has the dim lights. Again using the air compressor as the comparison. Compressor will run continuously if the demand is high. Pump get hot, tool has less torque, performance is degraded.

Same deal happening, as the alt tries to recover the battery loss. And because AMPs are HEAT ...... well 2+2 = hot alt. With solid state devices shutting down, if not going offline completely, out put is degraded .

Cheers,
pep
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Old 06-20-2018, 10:44 AM
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Quote:
Originally Posted by tools View Post
The alternator is grounded to the block. I have the battery in the trunk and grounded to the frame. Positive cable goes directly to starter where it connects to alternator wire.
possible that you need a ground wire from frame to engine
i too am a fan of the 1 wire alternator and suggest you keep a spare diode pack and regulator on hand
buy the good diode pack, i forget what the nomenclature is but it's made for the 100-140 apm alt
i believe eod guy helped me out when i went thru 2 oreillys rebuilds in as many weeks
i now keep spares with me on long runs, i can replace parts in a few minutes
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Old 06-20-2018, 12:31 PM
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Quote:
Originally Posted by rip-tide View Post
That is exactly what the problem is with the one wire set up. I say it a thousand times. One wire is for lawn mowers, tractors and gas powered welder type of operational conditions.


It is easily seen when a car is using the one wire deal. When looking at a line of cars stopped, the car with the dim & yellow head lights is the 1 wire set up. Three wire has the same intensity no matter what the RPM.

I not going to bother explaining the why, cause it has been over and over and over.

You will never have the problem with the 3 wire set up....... you're certainly free to ignore the advise.
pep
I probably didn't state this right. The problem is temperature related, getting into city traffic is a coincidence. With cold startup even at idle the output has a line voltage of 14.5. Then traveling on the interstate the voltage tapers as you'd expect but falls to 12 all the while the engine compartment is heating up as the engine reaches its 195 operating temp. Since it's summer there is nothing the electrical system has to feed on the highway other than the ignition, no AC, no stereo, no lights. This condition never relates to RPM and for now is survivable. Winter with dark when I leave and dark when I return and dim all day long requires running with lights and defroster so the battery alone will not keep up with this constant load of this condition with the alternator persists.

Currently, this being summer, when I get off the super slab to go into the big city I have to turn the cooling fans on. When that happens the voltage just slips away with no regard for engine RPM. But they only need to run for 15 to 20 minutes not all the time like the winter electrical loads.

Once the engine cools with a gauge reading of less than 195 the alternator is putting out 14.5 following start up. That lasts till the temp gauge hits 195 then back to no output regardless of RPM. This cycle just repeats through the day. The battery is obviously in good shape as for the few minutes it gets a full charge rate it keeps up with the demand of cranking the engine as needed without having to connect it to a charger. But that won't last forever.

This is the second or third GM one wire that has died in this exact same way in about as many years. So I expect that there is some generic fault in these things, perhaps given the mileage I put on in a year they just wear out in this time frame. I'm not researching this any deeper than an afternoon R&R job; but I am going back to the older three wire configuration simply because my history with those is they lasted longer. But as time and the industry mantra of "faster, better, cheaper" (with emphasis on faster and cheaper so 2 outta 3 ain't bad) continues it just might be that anything today just doesn't hold up to my expectations.

Bogie
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Old 06-20-2018, 01:29 PM
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For what it's worth, my 35 amp output alternator could not keep up with electric fans, A/C, power amp, and headlights, fresh air fan, etc.,, so after some research I got a chrome Proform 100 amp single wire (comes with a factory output test chart) from Advance Auto Parts and, BOOM, all electrical problems disappeared. Instant charging from the moment of startup, stable output. Just my two cents.
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Old 06-22-2018, 04:09 PM
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In my case I'm running a 120 amp alternator. It just doesn't put out when it warms up, the battery is in great shape so in traffic just running the ignition it is hard to see if the alternator is producing anything because the ignition just isn't a big drain.

But turn the fans on and you can see the discharge rate start to pull the battery down. And that is a drop that can be seen as staying there when the fans are shut off, not all of it but enough to see on the gauge.

Bogie
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