Alternator Gauge Reading High With 300 Watt Stereo System Installed---1969 Electrical System

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1969_Valiant

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Hi everyone. I installed a 300 watt stereo system in my 1969 Valiant with an original electrical system and my alternator gauge is running high. It's reading about the 3/4 mark, between the center sweet spot and max. I just replaced a dead battery and someone told me, I could be boiling it from overcharging, due to my system. He recommended that I get an upgraded alternator with a higher amperage rating. Would this solve my problem without creating others? Is there anything else that I might try before replacing the alternator? Thanks for the replies.
 
First, you may or may not have a charging problem regardless of the reading. The thing to do is get the battery "normalized" IE run it after starting with accessories......including the stereo.....OFF

Next with the engine warm and battery charged, read battery voltage with engine running to simulate "low to medium cruise" RPM. You should read 13.8....14.2, and not below 13.5 and not above about 14.8 FIX THAT FIRST. If it is high it most likely is a harness voltage drop issue. I've posted "a bunch" on this

After that, the high reading is likely because your junction point is on the "wrong side" of the ammeter connection, IE say, the starter relay. That will cause the wrong reading.. If you are going to run this high power stuff you have very little choice........if you tap off on the other side of your ammeter, NOW you have invoked the deadly "Mad electrical" disease, read this:

Catalog

So now you have a choice.........leave it as it is, and hope you don't do or have the kind of damage in the article, move the connection so the ammeter is happy, you will almost guarantee damage to the system.

You might want to think about going ahead and doing this mod or similar. Crackedback (member here) sells a jumper wire for this purpose.
 
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Upgrade the wiring at the bulkhead to the switch as well. I have replaced alllllllllllll the wires in my car now and have a 300 watt amp as well. My car (65 Valiant) runs half way on the ammeter. Gonna buy temp batt and oil gauges Friday, but mine stays where it was before. Idle the headlights dim but not as bad and I'm running the original alternator. No issues with mine. Have the alt. Checked then check it on the car with the stuff running. If your dropping a lot of voltage, go buy a capacitor. That'll save things better.
 
Oh, and when my battery is fully charged, I can run 65-70 and the ammeter is at half. Usually it's above halfway on throttle and cruising. Idle it's in the middle
 
Where is power for the system being sourced from?

If the starter relay or battery +, the ammeter is reading the additional load your stereo is pulling.

Don't buy another alternator to fix an issue that isn't the alternator.
 
Thanks for the detailed info. I'll borrow a meter from my friend the next time I'm over at his shop and see what kind of numbers I'm getting.

I have a 6 gauge cable running directly from my battery to the amp(with a fusible link in between).

Another friend who is good with stereos mentioned a capacitor, but he said that's only if the amp is cutting on and off or dimming my lights when bass hits at high volume. Neither is happening. My lights dim slightly at red lights because I have my idle turned down a bit, but that was happening before the system.

I'll start with the meter and go from there. Thanks a lot for your input. You guys are always a wealth of information.:thumbsup:
 
Your load is on the downstream side of the ammeter, so it's going to read high when the amp is turned on.

Turn it off and see what the ammeter reads, bet it's closer to the midline.

This is a big issue with mopars and where auxiliary equipment power is sourced in the car. I WOULD NOT continue to run the amp with the OEM wiring in place, carrying that load. If you must run it off the battery, run a direct charge line from alternator charge stud to starter relay or battery +.
 
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When doing audio in these old cars never use the factory wiring. They can't handle the current and will burn up. I've seen people loose their cars because they wanted a huge system in an old car. Only wire I used that was factory before I rewired it was the main hot wire. Otherwise I had new wires. The capacitor is not just for amp cutting out and lights dimming. It's so the battery doesn't get drained out and so your alternator isn't constantly trying to catch up and recharge the battery as hard. Get a cap on that if your running subs. You'll save the alternator and battery in your car. It's an added source of juice for the amp.
 
Well I'm not sure calling it an "added source" is accurate. The only source of "juice" is the alternator. Unless you add a battery charger and plug it into the grid, heehee.
But the capacitor can smooth out the power delivery between times when the sound material is not sucking electrons like a newly born baby on it's mothers breast.
But then, the battery should be able to do that job, on a 300 watt system.
Even banging out bass, the amp is only gonna put out it's max for say 50% of the time cuz bass is not a continuous draw but a pulsed draw. So even tho the amp may be required to put out 300 from one peak to the next, it may in fact only be pulling 1/10 of that between the pulses. Then you add the rest of the signals and maybe the amp only puts out an average of say 30 watts say, for the sake of argument. Ok and say the amp is just a typical 10% efficiency. That means even tho it is blasting out 300 from time to time, it is actually pulling more like 30/.10=300 from the alternator on a somewhat continuous basis. Ok so 300 watts at 13 volts say,is 23 amps. Badaboom!
And that old 69 alt is probably a 35 amp job. So even with the ignition running and the 69 headlights on, you still have a couple of amps to spare. A couple.
Here's the thing, If you pull all these amps thru the factory electro-mechanical regulator and the 35A alt, neither of them is gonna be excited to be doing that for long periods of time. Sooner or later the reg is gonna fry the points closed and put the alt into maximum overdrive, which is gonna have the battery boiling it's electrolyte awayin no time, and then it is toast. The alt., now having no shut-off is brazenly going to keep on pumping electrons, and they have to go somewhere. The alt. is just a big old electron pump now. So round and round they go and on every trip the wires get hotter and hotter, and hotter. Maybe you get lucky and the alt. fries itself first. Maybe you're not so lucky and the bulkhead connector catches fire first.

Ok so, the preventive maintenance is to get a bigger alt. that is capable of running like this, and switching over the regulation duties to the electronic type regulator, and running a big old cable straight to the battery to shunt this hi-current around all the factory wiring, and finally, install a big ol'battery that can take some abuse.
Of course with the bypass now installed, the Ammeter is ignorant of that so it kindof goes on vacation. You will need a different way of monitoring the system status.
Or you can install a big ol' relay on that shunt-wire, and trigger it from the ignition circuit.
Since the stereo will draw an average of maybe 23 amps, plus the regular load of lighting and ignition, the total might be right about 35A, and she is running 100%. To get your duty-cycle down to a more sane 50%, you might want to run a 70A alt, and that might take a different electronic reg than the stock 71 up type system. So research that. And then you will need two or three more things; 1) upgraded wiring throughout the system,from the battery thru the ignition sw, and to the stereo, and 2) probably a higher idle or a different set of pulleys, and 3) an on-board fire-extinguisher.

Ok that's my 2 cents.
 
In my 67 fish, I have a 200 watt head unit in the dash and a 200 watt Bazooka base cannon in the trunk. The head unit runs on OEM wiring and signals a relay that powers the Bazooka amp from alternate source/wiring. No charging system issues but... I had already upgraded to later model 65 amp isolated field charging system long before adding the jukebox.
 
Thanks again for the additional posts. Learning a lot here...maybe too much hahahaha. Now you guys are starting to scare me. Its ok. I ran around with a fuel leak spraying into the bottom of my ignition coil with a hole in it hahahahah. Yep true. Me and this car should already be dead..............a few times..........but I digress pffft hahahah. So another good mechanic friend of mine at my friends shop said that if I add a larger cable between the alt and battery, that it could help send more current to the battery from alt which is willing to give, but wiring can't send. He also said that my electrical system draws so little, that I have room(amps, volts, watts...whatever) to spare/play with. I understand the concept of a capacitor, it gets charged, holds charge, then discharged when needed n charged again waiting for a heavy draw. I'm actually at my friends shop now, but was playing with my a/f mixture on my carb and having a few beers:). I mentioned this whole thing to him and we will check it out sometime this week. Thanks again and again and again. I really appreciate the time and knowledge you're spending on me and my car:thankyou:
 
I just want to add this. If you're looking for some clean music, and doesn't drain the system, here's my setup.

All out of an 04 Audi s8
Bose 5 1/4s I cut into the doors run through Bose amp out of the Audi.
3 Bose 6x9s all in back deck run off
Kenwood cd deck

One Bose 10 inch flat sub out of an Acura MDX mounted in Harley Bagger Plastic Saddle bag. Run off sub side of Bose amp

Keep in mind I'm not done. Got it in and working and wires nicely done. Everything's mounted and ready for when I rip it all out and paint the trunk and interior. But it sounds damn good. Bass on CD player is at -5 and it hits good. I'm highly impressed and it's all nicely tucked out of the way without a huge box in the trunk.

Two 1inch tweeters I put in the dash. Just for the laughs and run off the rear channel of Bose amp.

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