Electrical problems? Lights dim
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Forum Name: General Discussion
Forum Discription: General Mobile Electronics Questions and Answers
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=35471
Printed Date: May 12, 2024 at 11:48 AM
Topic: Electrical problems? Lights dim
Posted By: smeenge
Subject: Electrical problems? Lights dim
Date Posted: July 12, 2004 at 4:39 PM
Ive got a 1967 Mustang Fastback in which i am going to be installing a modern stereo system with amps/subs/etc. Generally speaking it shouldnt be a problem since i have a brand new 70A alternator and Optima Red Top. I'll be running all the stereo equipment on its own fused connection to the battery.
But what concerns me is the car, as it exists right now, exhibits electrical quirks. The dome lights dim when the AM radio is turned on, the headlights pulse slightly as the engine idles, etc.
Ive already upgraded all the main engine compartment wiring (starter/alternator/battery/ground) with 4 gauge cables and the problems still exist. I suspect that perhaps the old crumbly 16-gauge wires behind the dash might be a culprit with a short? Its confusing because the amp/battery combo is more than enough for this car which has little to no electronics on board besides dome/dash lights and the horn.
So 2 questions:
A) Why is this occuring and how do i isolate it?
B) If I cant (or choose not to) isolate it, Will this affect my soon-to-begin-installing stereo system which will have a clean 4 gauge to the battery and a 4 gauge common ground to the chassis?
Replies:
Posted By: smeenge
Date Posted: July 14, 2004 at 11:49 PM
helpful forum... 
Posted By: maglin
Date Posted: July 15, 2004 at 8:07 AM
*chuckles* yeah... i'm not what you'd call a pro, but i have this old 1969 Opel GT AT with the 1.1L engine in it that i work on occassionally (my father's car). Its got a 35 amp Alt, and some crappy junkyard battery... dad is one of those types that buys it if it works, and not if it boasts all kinds of crazy features, like one of them optima red tops. anyways, the car idles sooo low that the alt actually won't charge the system, even with everything turned off. when you rev it up, it does just fine. Turn on the headlights, and you'r constantly draining the battery. SO. try turning up the idler, and see if spinning that alternator a bit quicker applies enough energy to the system. furthermore, check to see if your radio is on the same circuit as your courtesy lamps... i don't know if that would matter or not. might. Anytime i change a radio in a car, i create a all new circuit to power it, so its independantly on its own fuse and what not. I know that the geniuses who designed opel decided that the heater fan and the windshield wipers should be on the same circuit... needless to say, you gotta turn off one to run the other. I wish i could be more hlep, by i'm a true amatuer. ~~Dan
Posted By: smeenge
Date Posted: July 18, 2004 at 10:44 AM
That may well be the problem. Its no 1.1L, its a 7.4L 428 Cobra Jet with headers and barely street-legal exhaust system (read: louder than fukk), but i like to set idling like its about to stall, that way when i open the gas its like waking a sleeping giant and scares the sh*t out of everyone around.
Posted By: archemedes
Date Posted: July 18, 2004 at 5:19 PM
it sounds like your getting a draw, is the alternator the stock one? those only had about 50 amps stock. I would suggest upgrading the dash wiring a cooked mustang is a bad thing.
Posted By: TownAndcountry
Date Posted: July 19, 2004 at 9:20 PM
Your system will only be as good as your weakest link, meaning, is your ground wiring as big, if not bigger then the power? You could upgrade all the wiring, upgrade the alternator, add a cap, etc. But, if you add anything drawing current from the battery in addition to what is stock, the electrical system is not designed for that and has to be taken in account. I would add a seperate Power supply to the radio and amp. And, in conclusion, why are you listening to AM? -T&C.
Posted By: maglin
Date Posted: July 20, 2004 at 9:11 AM
LOL... knowing the weather and the latest scores on the Yankee's game is a valuble bit of information... Yeah... it's an itty bitty little thing, my car, but it runs, and looks cool... i *could* put a bigger engine in it... i've seen em done up with V8's (requires chopping the frame though)... i think squeezing in a 2.5 out of a firebird (thinks thats the size of them engines) would be more than enough to push this car over the edge... it weighs nothing as it is, and is actually kinda squirrely because of that... ~~Dan www.ctdg.org/dan/hobby/opelindex.html the red car is the one with the 1.1 in it...
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