74 electrical problems
Thread Starter
Racer
Joined: May 2009
Posts: 418
Likes: 1
From: South Florida fl
74 electrical problems
Can someone help with an electrical drain? I have a 74, 350, 200hp. No a/c or power brakes or power windows. Has power steering. Has a new alternator, battery. The charge will last about one to two days. If you drive at night it will start to bog down and die. Is there a problem with 74 electrical? Is there a test I can do or a test that a shop can do to find the drain? All info will be greatly appreciated. Joe
Le Mans Master
Joined: Aug 2006
Posts: 7,431
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From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
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Electrical Headache!
First thing to check is that the battery positive and ground connections are clean and tight.
On the alternator make sure that on the two wire connection that the brown wire is on the terminal near the fender (#1 terminal) and that the red wire is on the terminal nearest the motor (#2 terminal).
With the motor off voltage at the battery should be about 12.4 volts.
With the motor on voltage at the battery should be about 14.8 volts.
Next check that the light in the rear center compartment goes off when the lid is closed.
If thats all good then disconnect a battery cable and connect a test light between the battery terminal and the cable. If the light goes on then pull one fuse at a time untill the test light goes out. When the light goes out that is the circuit that has a problem and you have to figure out what part of that circuit has the problem.
On the alternator make sure that on the two wire connection that the brown wire is on the terminal near the fender (#1 terminal) and that the red wire is on the terminal nearest the motor (#2 terminal).
With the motor off voltage at the battery should be about 12.4 volts.
With the motor on voltage at the battery should be about 14.8 volts.
Next check that the light in the rear center compartment goes off when the lid is closed.
If thats all good then disconnect a battery cable and connect a test light between the battery terminal and the cable. If the light goes on then pull one fuse at a time untill the test light goes out. When the light goes out that is the circuit that has a problem and you have to figure out what part of that circuit has the problem.
Instructor
Joined: Sep 2008
Posts: 222
Likes: 0
From: penngrove ca
To check for draws I charge battery then disconnect neg. cable and check votage with a volt meter. Connect the + probe of meter to neg. cable and - probe of meter to neg. battery post. If it reads voltage you don't have a draw. If it reads zero then the fun begins with isolating circuits until you find. I'd start with the alt.
Racer
Joined: May 2001
Posts: 401
Likes: 0
From: Carlsbad CA
I just fixed the same problem on my '74. My battery wasn't charging because the fusible link that goes from the junction block (on the inside of the driver's side fender) to the alternator had melted. My battery wasn't charging at all. I'd charge the battery with a battery charger in my garage, and driving would discharge it to the point that it wouldn't start. I replaced the fusible link and everything works again.
I went through all the steps everyone else mentioned before I found the culprit. Needless to say I was pretty happy when I figured it out. If your ammeter on the dash doesn't jump into the postiive numbers when you first start your car, you probably have a charging problem like I did, not a short or draw. My alternator bench tested fine, and I tried every method of finding a short know to man.
Good luck.
I went through all the steps everyone else mentioned before I found the culprit. Needless to say I was pretty happy when I figured it out. If your ammeter on the dash doesn't jump into the postiive numbers when you first start your car, you probably have a charging problem like I did, not a short or draw. My alternator bench tested fine, and I tried every method of finding a short know to man.
Good luck.
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Thread Starter
Racer
Joined: May 2009
Posts: 418
Likes: 1
From: South Florida fl
To check for draws I charge battery then disconnect neg. cable and check votage with a volt meter. Connect the + probe of meter to neg. cable and - probe of meter to neg. battery post. If it reads voltage you don't have a draw. If it reads zero then the fun begins with isolating circuits until you find. I'd start with the alt.
