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OPEL-LESS!!!
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Discussion Starter · #1 ·
i know the GT has a weak alternator from factory, 28AMP if i remember right. do you think a 630 CCA battery and a stock alternator could keep up with a mild sterio, and my mild i mean very mild, just a pioneer deck with 2 6X9's and 2 4's. no amp or subs. i would like to add a set of decent fog lights int he bottom of the bellypan, nothing too big but not cheapos, and i would like black or blue neons int he "nostrils" to go with the blue dots/stripe, do you think this would be ok while running the headlights and such with sterio all at the same time or would i have to upgrade to the 65 amp?
 

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G.smurf, if I remember rightly, you can get it rewired for better performance. Just need to find a motor rewire shop and ask them what they know about it. Unless you can find a heavier amp at a parts store. I haven't tried to replace one for....hmm, since before you was born. But I thought I'd pass that to ya. Sorry not more helpful.
 

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Jared, run a search for alternator mods, I believe there have been ample threads on putting in a 100 amp GM one wire on Opels in the past. If memory serves, I think you also have to use the amp light to get the alternator to generate the amps because it is internally regulated. HTH.

Ron
 

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OPEL-LESS!!!
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Discussion Starter · #4 ·
i know i have sources of information to change them, just trying to figure out if i need to change them or not.
 

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I guess the way to find out is to get everything installed, turn it all on, run the engine to about 1200-1800 RPM and see what the amp gage says. If it goes to the positive side you're O.K. If it does not move from the center or goes to the negative side, it's time for a change:)

Ron
 

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OPEL-LESS!!!
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Discussion Starter · #6 ·
hmmm. it barely comes of zero right now. charges at almost 30 when you first start it and then after a minute or two it drops down, stays at like 1 or maybe 2 amps.
 

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Earlier Opels had 28 amp alternators, until 1971 when the rear window defroster-equipped cars came with 35 amp units. After 1972 they all came with 35 amp alternators, until 1975 when they were upgraded to 45 amp models.

So lets do some figuring. Even at 28 amps and 14 volts it is putting out almost 400 watts. The high beams take about 110 watts, and all the running lights use maybe another 25 watts. The ignition coil takes 50 watts maximum and the heater fan another 50 watts. The rear window defroster is another 100 watts. So that means the total load may be as much as 335 watts, BEFORE you turn on the stereo. But to answer your question, yes, it will probably be sufficient. Although many low end stereos are rated at "100 watts per side", they seldom consume more than 20 to 50 watts continuous. You won't have much reserve, but it will work.

The best thing to improve, short of replacing your alternator with a 45 or even 100 amp unit, is to install an electronic voltage regulator. There is no substitute for a FULL 14 volts, and many mechanical voltage regulators respond too slowly to maintain peak output. I have also seen some electronic voltage regulators that have an adjustable "tap", to ensure that you get a full 14 volts at the fuse box.

HTH
 

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Jared, that's the way an alternator is supposed to work. It senses voltage via the regulator and charges to the needed output and slowly tapers off as required. It appears your charging system is functioning correctly. But, it may or may not be enough for all you're going to put in the car. Keith is right you may need an electronic regulator. HTH.

Ron
 

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Keith,

You missed one piece of the puzzle in your estimation, which is that the alternator doesn't put out full current under all conditions. Here's a couple alternator output graphs. They will obviously vary greatly from car to car but the overall shape of the graph will remain the same.

http://www.motorvate.ca/mvp.php/521

http://www.humvee.net/hidgraph/alt-out.jpg

While cruising on the highway it isn't going to matter much, but in stop and go traffic it will significantly reduce the amount of power output...

-Travis
 

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You can always try it and see what happens. You arent asking all the much more from it, but it would be nice to have some extra power incase you 'upgraded' something in the future. If you upgrade the ground from the engine to chassis and battery to chassis, and alt to battery with larger gauge wire (go ahead and use something overkill like 1/0 guage) the electrical will be happier and you might be fine with that stock alt for a while. Again I would try it, if you get into headlight dimming then think about a larger alt and/or larger battery.
 

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Travis,

Yea, I was trying to keep it somewhat simple. But the low rating of this alternator probably results in a quite flat output curve. In fact, I doubt that the factory 28 amp alternator peaks at only 28 amps. It is probably somewhat above that at higher rpm.

I also probably overestimated the coil draw (I used the amperage draw quoted in the FSM, at 3.8 amps when stopped, compared to 2.3 amps when idling, although that is quoted at 12.5 volts (due to the resistor wire, I suspect). So the load due to that item may only be 30 watts or less. I also added the 100 watts for the rear window defroster, that would be matched up to a 35 amp alternator, which puts out another 100 watts.

Whatever. Jared, with a basic stereo, and no huge auxiliary load, you should be fine. Even your fog-lights should work (since they are supposed to be wired up to light only when the low beams are on). I don't know about neon lights, but so long as they aren't more than 100 watts or so (7 amps), you should still be OK.

Another suggestion? Install a digital voltmeter. If your voltage drops below 12 volts, you aren't keeping up to the load.

HTH
 

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OPEL-LESS!!!
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Discussion Starter · #12 ·
well its a 71 with the origional alternator, i just spent 2 hours making it look like new. but my car didnt have the rear defroster, and manufacture date is 9-70....all the block, head, tranny, any casting number says 70 so i'm not sure if i have the 28 amp or 35 amp. i'll just try it and see what happens tho. thanks alot guys.
 

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OPEL-LESS!!!
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Discussion Starter · #13 ·
i got a set of foglights for it and hid them in the bellypan, 55W, not sure of the amps, didnt see it. when i have my low beams on, and turn the fog lights on, amp meter dropped from charging at 20 amps, to 10 amps, drove about half hour with them last night and stayed positive. i'm not doing the neons, too rice boy looking, and thats what i want to stay away from most. i'm trying to get a classic sports car image, but i figured fog lights were a must, the early AM hours here get foggy as hell, especially where the swamps and such meat the roads edge.
 

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boomerang opeler
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hi jared
one thing i found of use from the frogs in france is to coat the frog sorry fog lights amber/yellow as you see on a european gt
the colour seems to cut right through fog and give a much better depth perception
don't know why but it dose work also don't know if legal in US but if you have swamps its worth a quick check with the law to see
 

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Baz. Yellow fog lights are legal in the U.S. I prefer these over clear anyday since they don't "reflect" the fog as much as the clear.
 

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OPEL-LESS!!!
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Discussion Starter · #16 ·
well i guess the alternator can't keep up for longer periods of time. i know the exact route i must take for my drivers test on friday, getting my liscence finally on wednesday the 14th!!!. anyway, i was running through the exact route to make sure i remembered all the little surprises, GT does not like highways, 3500RPM just to do 65.....the alternator dropped down to
-20AMPS at a stop light, so i shut them off, probably driving abouta half hour on backroads. i suspect i have a higher volt alternator, just a suspicion as the front pully is a different style. instead of the blades being open, the front is smooth, hard to explain but if you look at it, it almost looks like a vented rotor if you know what i mean, smooth outer surface with the fins enclosed within. autozone tests them for free supposedly, so i guess i'll get it checked out.
 

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namba209

I remember upgrading an old datson 510 to a GM 100amphere alternator but I did have a full schematic (for both) to work from.

If those specs are really listed somwhere simply (splice blue to white and bromn/w/strip to black) that would save me some time.

I promise to post my results as I am upgrading my alternator soon anyway (for the same reason... more lights=less moose)
 

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Joseph T, run a search for alternator upgrade on this site. I'm pretty sure someone has done it here, if not, check out the classic opels siite on Yahoo. If I get the time later tonight I'll check out my DESTEC and Camaro schematics and see if I can get you the correct colors to connect.

Ron
 

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Congrats!

Congratulations on getting the license! It is very cool. I think it is awsome that your GT is going to be your first car! Good Job
 

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OPEL-LESS!!!
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Discussion Starter · #20 ·
Chad....its really my 9th car, out of 14 cars, but only my 4throad worthy car..........first was a 70 GT, second was a 82 chevy, then this, and now the most recent driver is a 72 auto GT, got it for free!!! wow, too many cars for my age...haha.
 
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