76 Vette - Battery drain
Thread Starter
Advanced
Joined: Oct 2008
Posts: 63
Likes: 2
76 Vette - Battery drain
I know there is a lot of threads covering this topic but I have what I think is an strange issue or may be normal. My car went completely dead over night but track it down to leaving the clove box open, really didn't think it should drain the battery over one night so I decided to use the test light and check if there was any other items draining the battery. I found the light would pulse on and off, it was like turning on your blinker. When I pull the curtesy fuse it would stop. I have a quarts clock so I disconnect, but it wasn't the clock. Turns out my radio is causing this issue, its just a JVC so nothing special. I replaced the radio with another JVC, didn't want to change the plug, double checked the wires are correct, so the constant power is going correctly to the correct wire, and the ignition switch is also correct, ground looks to be good as well. Any ideas is to why the test light pulses (its not the LED light)? Is this normal?
Thread Starter
Advanced
Joined: Oct 2008
Posts: 63
Likes: 2
Ok, I'll use a amp meter, to check how high the draw goes. But it seems strange I would get any fluctuation in power. I don't have the timer for the lights. When I close the doors the lights go off, no delay.
Melting Slicks
Joined: May 2021
Posts: 2,274
Likes: 1,318
From: Fleming Island, FL
Leave the amp meter connected for at least 5 minutes to let whatever circuits to charge up. In my experience most amp meters that are rated to read 0 to 200ma will read higher than 200ma but amp meter with a 0 to 10 or 20 amp scale would be preferable. A 200ma draw is about what a glove box bulb (194) draws.
Thread Starter
Advanced
Joined: Oct 2008
Posts: 63
Likes: 2
I would have to pick up a new amp meter, but I can tell with the test light it illuminates every 4 seconds without fail only when the radio is connected. I triple checked the wiring and it is 100% correct. I guess we need to see what the draw is to be sure. But would draw power every 4 seconds. Bulb goes dark then lights up every 4 seconds.
Thread Starter
Advanced
Joined: Oct 2008
Posts: 63
Likes: 2
Update, I was thinking maybe I had the curtesy delay and it wasn't working, broken. When I tried to find out where it would be on a 76, since 77 had it above the steering column but could not find any real documents for the 76. I did find one place that said it was behind the glove compartment. I don't even think the 76 had a delay for the interior lights. Anyway there was a module (HOBBS 6258257). When I pulled it out the I have no drain, light stays off. Looking at the part number shows it to be a seat belt buzzer. Anyway I have no idea at this point, but that seams to be the culprit. Since I have no switches to say if my seat belts are connected or not I will leave out the module. Why this only happens with the radio connected I have not figured out, maybe someone can elaborate. But I think it is fixed.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Race Director
Joined: Mar 2017
Posts: 11,949
Likes: 4,507
From: Virginia
I've seen many radios that pulse a red LED in the car, either as part of the real anti-theft system, or a fake one.
Where are you connecting your ammeter? My Fluke will do 10 Amps, but I'd never connect it to my car. I use a Fuse Buddy instead (Amazon link, may require some effort to make work with glass fuses). 100 mA or less? I don't care about that. I have a battery quick disconnect instead. If you have a bigger drain, and you can't find it in a fused circuit, it is likely the alternator.
Where are you connecting your ammeter? My Fluke will do 10 Amps, but I'd never connect it to my car. I use a Fuse Buddy instead (Amazon link, may require some effort to make work with glass fuses). 100 mA or less? I don't care about that. I have a battery quick disconnect instead. If you have a bigger drain, and you can't find it in a fused circuit, it is likely the alternator.
Thread Starter
Advanced
Joined: Oct 2008
Posts: 63
Likes: 2
This is what I found with the AMP meter.
Set it at 10 AMPS, connected the meter in series. (black wire disconnected form battery, touched negative side of battery with one lead then the other to the disconnected battery wire).
After a couple of seconds I get the spike to .3 amps. Then it slowly drains down to .01 (I assume the quarts clock).
It doesn't fluctuate after that just stays at .01 and I also connect light tester and it stays off.
Seems like the amp meter drains what ever is causing the spike.
But it comes back once I disconnect the amp meter. So I definitely have some kind of problem but this is only when the radio is connected.
I know the radio is connected correctly.
Set it at 10 AMPS, connected the meter in series. (black wire disconnected form battery, touched negative side of battery with one lead then the other to the disconnected battery wire).
After a couple of seconds I get the spike to .3 amps. Then it slowly drains down to .01 (I assume the quarts clock).
It doesn't fluctuate after that just stays at .01 and I also connect light tester and it stays off.
Seems like the amp meter drains what ever is causing the spike.
But it comes back once I disconnect the amp meter. So I definitely have some kind of problem but this is only when the radio is connected.
I know the radio is connected correctly.
Melting Slicks
Joined: May 2021
Posts: 2,274
Likes: 1,318
From: Fleming Island, FL
You're good with the 10ma draw, nothing to worry about. The 300ma when you first connect it are just charging the memory circuits. That will happen every time the battery is reconnected.