a narrowed down 1974 electrical problem
Thread Starter
Instructor
Joined: Jan 2005
Posts: 146
Likes: 1
From: Roanoke Rapids NC
a narrowed down 1974 electrical problem
I've been fighting a battery drain which i am certain is on the fuse labelled "tail". i know the tail lights as well as all the running/parking lights are on this fuse. I pulled every bulb on the car and it didn't kill the drain. There were a few bulbs that i had to replace but i put i all back together and now the drain is still there but the lights won't work! i know the bulbs are good because turn signals and hazard lights (which use the same bulbs but are on a different fuse) still work. The only other thing i messed with was to replace a fusible link which i thought was on a line that ran from the clip on the side of the alternator to a positive lead junction where about 5 big positive leads meet up on one stud mounted on the inside left fender. BTW the "tail" fuse has not blown. I feel so close, yet so far, please help.
thanks,
Brad
thanks,
Brad
Racer
Joined: Sep 2005
Posts: 407
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From: Fort Washington PA
I don't drive my car that much so the battery drains all the time. I got a quick disconnect and a small charger that I now use. Turns out it was the clock. I replaced my radio with one that require power all the time but all my pre-set stations have to be re-programmed, but at least I can start it.
Thread Starter
Instructor
Joined: Jan 2005
Posts: 146
Likes: 1
From: Roanoke Rapids NC
i can worry about the drain anytime, right now i need to get my tail and parking lights back working. I am getting 12 volts at both ends of the tail fuse so i'm assuming the problem is from the fuse box to the back of the car. I did say i replaced some bulbs. But why would they work for the other functions like hazard, turn signal, etc but not regular night time use for lights?
Thread Starter
Instructor
Joined: Jan 2005
Posts: 146
Likes: 1
From: Roanoke Rapids NC
***UPDATE****
alright fellows,
tonight i managed to get the tail lights back working flawlessly. It was a goof on my part. Anywho, I've narrowed down the drain to a single wire. It is a small black wire with a white pin stripe that is connected to the hotwire running from the starter around the engine and to the power junction mounted on the left inner fender. The small black wire is connected to the hotwire right where the hotwire meets the junction. The small black wire then runs into the firewall near about where the fuseblock is on the other side. Anybody have any clue what this small black wire with a white pinstripe is for?? the volt meter gauge perhaps?
thanks all,
Brad
alright fellows,
tonight i managed to get the tail lights back working flawlessly. It was a goof on my part. Anywho, I've narrowed down the drain to a single wire. It is a small black wire with a white pin stripe that is connected to the hotwire running from the starter around the engine and to the power junction mounted on the left inner fender. The small black wire is connected to the hotwire right where the hotwire meets the junction. The small black wire then runs into the firewall near about where the fuseblock is on the other side. Anybody have any clue what this small black wire with a white pinstripe is for?? the volt meter gauge perhaps?
thanks all,
Brad
Thread Starter
Instructor
Joined: Jan 2005
Posts: 146
Likes: 1
From: Roanoke Rapids NC
i'm one step ahead of you partner, i unplugged the alternator and the drain was still there so i am assuming it is the amp meter. then that must mean the amp meter runs through the tail fuse. which would make sense because its always hot while the other guages are turn key hot. I'll try unplugging the amp meter tomorrow and see if the drain goes away. Thanks for the help guys, i know you all know how frustrating these darn electrical bugs can be, if it is as simple as unplugging the amp meter i will be a happy camper. 
Race Director
Joined: May 2006
Posts: 16,528
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From: Dayton, Ohio
i'm one step ahead of you partner, i unplugged the alternator and the drain was still there so i am assuming it is the amp meter. then that must mean the amp meter runs through the tail fuse. which would make sense because its always hot while the other guages are turn key hot. I'll try unplugging the amp meter tomorrow and see if the drain goes away. Thanks for the help guys, i know you all know how frustrating these darn electrical bugs can be, if it is as simple as unplugging the amp meter i will be a happy camper.
Thread Starter
Instructor
Joined: Jan 2005
Posts: 146
Likes: 1
From: Roanoke Rapids NC
i'm using an old multimeter and i have it set on the 10 amp position. i unhooked the negative battery cable and put the positive probe on the cable and the negative on the battery terminal. It obviously works because i can see it going up or down with the various lights and all turning on or off. after cleaning all the connections and putting it all back together the draw almost looks less that what it did before but theres still a little bit there, i'll try unplugging the amp meter and let you know what happened.
thanks,
Brad
thanks,
Brad
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Melting Slicks
Joined: Apr 2006
Posts: 2,211
Likes: 64
From: Bocabec, New Brunswick
I don't have the wiring diagram for a '74 but if I recall correctly in early charging systems if there was an amp meter then it was part of the charging circuit. It provided the resistance for the reference voltage on the voltage regulator. If the amp meter is not connected I don't think you will get charging from the alternator.
Thread Starter
Instructor
Joined: Jan 2005
Posts: 146
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From: Roanoke Rapids NC
oh ok thanks for the info, i had already tried to disconnect the meter anyway and it didn't kill the drain so, oh well. The drain is only 0.08 amps. is that enough to kill a battery over a few days or do you think i have another intermittant short somewhere else? i knew i could wiggle the door jam switch for the interior lights and it would increase the draw so i took it out and cleaned it well and it works now. maybe that could have been killing it? if i ordered a year specific wiring diagram would it tell me exactly what comes off of the tail circuit so i could track down the problem?
thanks,
Brad
thanks,
Brad
Le Mans Master
Joined: Jan 2006
Posts: 9,192
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From: Boca Raton Florida
.08 should not kill the battery in a few days, you may have fixed the issue with the door switch. The year specific drawing should tell you what you want to know. Zip has a pretty good color drawing and there is a member in here, Don Oleson he also had a good one.
Race Director
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From: Dayton, Ohio
Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
Thats correct so a .08 current is 80ma and that should be ok. A battery with 200CCA should be able to sustain that discharge rate for some 2000 hrs. The battery charge will disipate internally faster than that.
Race Director
Joined: May 2006
Posts: 16,528
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From: Dayton, Ohio
Thanks guys I think I have it now.This getting old is for the birds.I guess thats why I have to use a test light to check for battery drain.I wonder what my test light will detect when it is barely glowing?I think I'll go put a meter on it.Thanks again.
Thread Starter
Instructor
Joined: Jan 2005
Posts: 146
Likes: 1
From: Roanoke Rapids NC
well shoot fellows, if ya'll are doin the math right then i should have nothing to worry about because i have an Optima Red top dry cell battery thats rated at 720 cca. hopefully it was that door jam switch. I noticed that the charging system is working way better than before so hopefully that will help too. thanks again all!
Brad
Brad