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· Senior Contributor
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a while back someone asked me at a car show if my car(1971 opel gt) had the alternator or the generator. well i hesitated and said alternator. well whats the difference? the reason i ask this is because my battery is keep going dead, and not because the battery is bad. i tested the alternator and am getting a reading of 0 amps. thats probably why my battery goes dead every two weeks. that or i have to much new stuff on my car for that little 35 amp to charge.( sterio and newer interior lighting.) well what ever the case maybe i'm gonna need more power for the stuff, so i found a 90 amp "generator " from www.rockauto.com for $67. i just need to know the difference in the alternator and generator, if any???? basically will this work on my car? thanks in advance,

Billy
 

· boomerang opeler
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you were right to say alt billy
a generator is a dynamo and was used on even older cars it makes DC current and is rev dependant to make power
an altinator is making AC current and has a bunch of diodes that convert the AC to DC , they also make power from idle which is better for a car
it may be cheap enough to have the alt rebuilt but if the 90 amp one is that price then its a great help if you run amps for ICEand need the extra power
i think a few folks were chatting last year4 about using the GM 1 wire alt (gets rid of that box on the side frame with the 3 wires running to it ) try a search and see whats there for it
 

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Both an alternator and a generator are RPM dependant on the amount of current they can produce. An alternator rated for 90 amps will not produce the full 90 amps at idle. Different model alternators have different kick in points, or the RPM that they start to produce power and different power curves. The GM alternator conversion addressed elsewhere on the site actually takes advantage of this feature because an alternator designed for a larger engine starts producing at a lower RPM range because larger engines usually idle at a lower RPM.

The major difference between an alternator and a generator is how they are constructed and how the current is drawn from the device. A typical generator is limited to low speed operation due to the way they are designed. The way an alternator is designed it can handle higher RPMs. This is an advantage because an alternator can be geared up and produce more current at a slower engine RPM then a comparable generator. Generators work best when kept at a constant speed or in a narrow RPM range. If you look at older cars with a generator you will see that the generator pulley is almost always larger in diameter then a comparable alternator pulley which slows the generator input shaft.
hth
Brian
 

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Alternator idiot light

Willy_g77 said:
a while back someone asked me at a car show if my car(1971 opel gt) had the alternator or the generator. well i hesitated and said alternator. well whats the difference? the reason i ask this is because my battery is keep going dead, and not because the battery is bad. i tested the alternator and am getting a reading of 0 amps. thats probably why my battery goes dead every two weeks. that or i have to much new stuff on my car for that little 35 amp to charge.( sterio and newer interior lighting.) well what ever the case maybe i'm gonna need more power for the stuff, so i found a 90 amp "generator " from www.rockauto.com for $67. i just need to know the difference in the alternator and generator, if any???? basically will this work on my car? thanks in advance,

Billy
When you turn your ignition key on, does the idiot light in the ammeter come on? If not, your alternator WILL NOT CHARGE!!! :eek: This circuit (blue/white wire) is the "tickler" circuit for the regulator and the 12V it supplies "starts" the regulator function. The idiot light is similar to a fuse. If burned out, the regulator doesn't "start" and the alternator won't ever "charge"!
 

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Otto is right on there. Even if you got the higher amp GM one wire alternator, you will still need that lite in the ammeter workiing for the upgrade to work. It is the signal or differential voltage from that lite that "turns" the alternator on, so to speak.
 

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Discussion Starter · #6 ·
i have a push button start. but i still have to use the key and turn it before pressing the button. well that being said, when i turn the key to the on position the amp and oil lights come on. but after starting the car they both go off, if im not mistaken.just tired of my battery going dead from only cranking it only a few seconds... yes i gotta story now...happened more than once.

i started my car up and it started and drove fine, got it to the gas station, filled her up and went to pay come back out trying to start it and the battery wouldnt have enough to started it up again. and i know part of the hard start is because of something like vapor locking. thats with 32/36 electric choke.

im going to add pertronix here soon with flamethrower coil. and was wondering if that is going to eat more power from the battery?. and would a good 35 amp alternator handle 160 watt radio, l.e.d. interior lighting, and electric choke along with future upgrades such as the petronix ignitor and fog lights?
 

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I have upgrade to the GM "CS" 105 amp alternator it has a higher output at idle than the "SI" 63amp alt. normally used for this upgrade and is smaller in size than the org. Opel alt. The bottom alt. bracket is replaced with a chevy. bracket ( chrome with bolts #42273 $7.99 at Pep-boys a/parts)and a spacer is used to move alt. to front of eng. and shorter bolts to Opel block. You can use the org. Opel adjusting bracket with a spacer .My alt. was a rebuilt unit but you can find these in a salvage yard( if you do be sure to take the alt. plug-in ..it is a four wire connector )the alt. is for a '91 C/K 1500 Chevy Truck w/350v8 A/C TBI ( Autozone #DLG1345-6-7 )You will need to swap your pulley ( this alt. has a serpentine belt pulley ) no grinding is needed except on the front bolt hole on the lower mount bracket to match the Opel block .The wiring used is the "one wire setup " the connector body has indentification letters "S" "F" "L" "P" The "S" wire is a heavy red wire that is connected back to the alt. output The "L" wire is connected to the Opel Waring lamp wire . F&P wires are not used You cut the org. Opel harness and use only to wire in the Opel waring light circuit
to the "L" wire and then connect the org. Opel wire for the output ( fusablelink red ) to the new alt. and your are done .. you can now remove the Opel voltage regulator . There are many other GM alt. & connectors but these were the ones I used . If you need a connector it is at Pep-boy #85118 at $24.99 . I have some photos posted in the gallery . HTH
:eek:
 

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namba209 said:
Otto is right on there. Even if you got the higher amp GM one wire alternator, you will still need that lite in the ammeter workiing for the upgrade to work. It is the signal or differential voltage from that lite that "turns" the alternator on, so to speak.
Unless the alternator is one of the self exciting models that uses the residual magnetic field created by the battery to determine when
to turn the alternator on. Then the light is redundant.
hth
Brian
 

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On the "CS" 105 amp alt. I use the Opel waring light circuit on terminal "L"
to turn on the alt. The "CS" type alt. uses a built in voltage regulator with fault detection.If you donot use the Opel waring light then you would need to add a 15 ohm res. to a ing.run circuit to turn alt. on .HTH
 

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Willy_g77 said:
im going to add pertronix here soon with flamethrower coil. and was wondering if that is going to eat more power from the battery?. and would a good 35 amp alternator handle 160 watt radio, l.e.d. interior lighting, and electric choke along with future upgrades such as the petronix ignitor and fog lights?
160 watt radio will take 13 amps at the very most, but when its turned up all the way, using as much power as possible, it will only be about an average of 6-7 amps, varying with the loudness of the music... if that makes sense

LED lighting will take next to no power, since they are extremely efficient

i'm not sure about the pertronix and electric choke, but i wouldn't imagine they would take too much, and the fog lights shouldn't take more than a couple amps

so i guess the 35 amp alt should work, but its pushing it since it won't be making 35 amps all the time, i would reccomend getting something better... it would be worth it
 

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simplemind7 said:
160 watt radio will take 13 amps at the very most, but when its turned up all the way, using as much power as possible, it will only be about an average of 6-7 amps, varying with the loudness of the music... if that makes sense
No it doesn't

The input voltage and current draw of a radio do not determine the total audio wattage output of a system. So you can't say a 160 watt radio will draw 13 amps at 12 vdc, (P = I x E or Power = Current x Voltage) using the example above 160watts = 13amps x 12vdc.

The impedance of the speakers used will drastically change the wattage output of any audio system. A 160 watt rated system may put out a peak rating of 160 watts (audio power) with 4 ohm speakers but only 80 watts with 8 ohm speakers. Input current draw will be the same.

As the peak and RMS ratings for an audio system increase the DC current required to drive the system will also increase but there is no direct correlation between the input current and the power rating of the audio signal.

Brian
 

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Throw in the fact that most linear amps are only 70-85% efficient and the number goes up even further. I used to install high end auto sound systems and always ran a heavy fused wire direct from the battery to the amps, just to get a good high current supply.
 

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These high amp draws , blower on high, rear defog on , wipers on high , headlights on and stuck in traffic :mad: are the reasons I went to the 105
amp upgrade , All just stock equipment .. and then add fog lights, cooling fan and a/c ..now something else is needed that will keep up .. 105 amps works for me .HTH
 
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