Electrical Expert Needed ASAP
#2688797
08/17/19 04:55 PM
08/17/19 04:55 PM
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Joined: Feb 2005
Posts: 957 MI, Lapeer
maximus
OP
super stock
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OP
super stock
Joined: Feb 2005
Posts: 957
MI, Lapeer
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I am no electrical expert but I can wire up a car off diagrams. I have an electrical problem and need troubleshooting help. Please read carefully for all I have done so far. The car is a 1968 Hemi Dart clone and has been driven about 200 miles so far. The car ran fine until two days ago when I went to start it up. The fuseable link blew going from the starter relay to the bulkhead which sends power to the ammeter.gauge. The opposite side of the ammeter uses common power to the Alternator Battery post, the ignition switch battery post, the headlamp switch, horn relay and two fuses in the fuse box according to the diagram.
1) I had the alternator tested for grounding and it checked out fine.
2) I used test light between the bulkhead and the starter relay where the fuseable link would go, and no light, fine.
3) Turned the ignition switch to on position and test light went on, meaning a ground somewhere?
4) Disconnected the wires one at a time to feeds, first the alternator, then headlight switch, horn relay. Test light stayed on.
5) No blown fuses in fuse box so that is OK.
Question, can the ignition switch be bad? Is there a way to test it?
Where do I go from here?
The complete wiring system was checked for breaks or bad wiring before installing into the car. Everything was working fine. The car does have a MSD ignition installed if that means anything with the problem.
Car will start right up with new fuseable link, only for 5 seconds, at which time the link blows.
Wire going from starter relay is 10 gauge and fuseable link is 16 gauge. Other side of bulkhead is 12 gauge per diagrams.
Any help would be appreciated to solve this problem.
I HATE ELECTRICAL PROBLEMS.
Last edited by maximus; 08/17/19 05:28 PM.
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Re: Electrical Expert Needed ASAP
[Re: stumpy]
#2688801
08/17/19 05:10 PM
08/17/19 05:10 PM
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Joined: Feb 2005
Posts: 957 MI, Lapeer
maximus
OP
super stock
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OP
super stock
Joined: Feb 2005
Posts: 957
MI, Lapeer
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According to the electrical diagram the wire from the bulkhead/ fuseable link then goes to the ammeter The other side of the ammeter is common to the other connections. This is looking at the diagram. What I am saying the car was working fine until this issue arose. Does some have another diagram for a 1968 Dart they can look at.
Last edited by maximus; 08/17/19 05:32 PM.
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Re: Electrical Expert Needed ASAP
[Re: maximus]
#2689286
08/19/19 07:56 AM
08/19/19 07:56 AM
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Joined: Feb 2010
Posts: 1,645 Phila. Pa.
Mattax
top fuel
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top fuel
Joined: Feb 2010
Posts: 1,645
Phila. Pa.
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Placed new link in, turned key to run position for 20 seconds nothing happened to link. This is not a good way to test for shorts to ground in the main circuit!!! Unhook the battery, disconnect the main wire to the alternator, tape it up so it will not short out on something , reconnect the battery start up the engine, You may have an intermittent short in the alternator that only occurs once it warms up a bit. This is not likely but definately possible. Same concept but more likely its in the 'ignition' or 'accessory' circuits. I put those in quotes because those are really the feeds for all power that gets switched on with the key turned to RUN. Maybe slightly more likely is a loose battery plate. When the alternator is producing power the battery sucks it for all its got. And if its a bigger alternator, like a '60 amps' then after a couple minutes of 50 - 60 amps, the link melts. This would show as the ammeter pegged to the charge side. if you don't mind blowing another fusable link, can you see if it blows with just the car in run vs actually running?
and when it blows are you just at idle? or did you rev the engine any?
If no fuses blow, then you can probably eliminate those circuits, but for fun in case it is a cumulative issue, could you pull all your fuses as well. ... This makes no sense. The fusible link protects against battery shorting in any of the unprotected circuits. Most important it protects in case the battery shorts to ground. If there is a ground short in any circuit after a fuse or breaker, those will fail long before a 16 gage wire melts). That 16 gage wire can handle all normal power needs for the car if you have to limp home on battery power. Even 30 or 40 amps for short periods of time will not degrade it. Just don't be putting 30 - 40 amps through it continuously. But that's not the issue here. There's a couple ways to safely hunt for the short with the battery connected. One is to install a circuit breaker where the fusible link goes. Chrysler suggested their techs use a flasher unit. Another is to wire up a '12 V' light bulb and place that where the link goes. (Test light, but not internally battery powered) With the battery disconnected, you can try a continuity tester. This can be a battery powered test light light, or a multimeter with resistance or continuity measuring, Lets go over the information so far. Dome light: As Lusk said, the door switch completes the circuit to ground. This circuit is hot all the time, but is protected by a fuse. Key in Run: This makes both the ignition 1 (run) feed hot, and the accessory feed hot. Accessory feed goes to fuse box, windshield wipers, and a few other 'accessories' Battery installed: This makes the entire main circuit hot all the time, ( plus the feed to the starter motor). If there was a short in the alternator output wire, or the wire leading to the key switch, or to headlight switch B1 terminal, the fusible link would have melted as soon as the battery went in. An observation of the ammeter would be a useful clue as to where the short is located. http://www.heritech.org/cuda/Charge2.html Below is a basic late 60s A-body scheme: MSD 6 traditionally was switched on by removing the power wire from the coil and connecting to the MSD 'on' wire. This must be isolated from the coil and ground. The MSD 6 often drew its power by connecting at the battery positive or the starter relay stud. Alternator output stud would be OK too. If you're doing early MSD, like the 505BC, I'd have to check if the wiring is the same.
Last edited by Mattax; 08/19/19 08:05 AM.
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Re: Electrical Expert Needed ASAP
[Re: Mattax]
#2689329
08/19/19 10:28 AM
08/19/19 10:28 AM
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Joined: Jan 2006
Posts: 3,535 Canuckville
68Cbarge
master
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master
Joined: Jan 2006
Posts: 3,535
Canuckville
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Jump a wire from battery output stud back of alternator and connect to battery stud of starter RELAY. Make sure you run an inline fuse or fusible link at the end of the wire at the relay. If everything works normally the ammeter gauge is NFG. You can run the car like this forever if you do not want to pull the cluster to replace ammeter and run an aftermarket 12 volt guage in the car Hope this helps
Last edited by 68Cbarge; 08/19/19 10:30 AM. Reason: sphellng
'68 Newport Custom Barge on a Budget!! BOAB 1973 Satellite WAGON! 318- 3 on the tree!! 2008 Chrysler 300c HEMI!
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Re: Electrical Expert Needed ASAP
[Re: maximus]
#2689398
08/19/19 02:02 PM
08/19/19 02:02 PM
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Joined: May 2008
Posts: 5,399 Aurora, Colorado
451Mopar
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master
Joined: May 2008
Posts: 5,399
Aurora, Colorado
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If no current, Fuseable link OK with key off, then the ammeter, constant power circuits and alternator output circuits are not causing the problem.
Check in the ACC (accessory) position, and if no problems, then the problem is likely in the engine wiring harness. If the fuse blows in the ACC position, issue is in the Accessory interior wiring, check ignition switch to fuse block.
If problem only in RUN position, check connections at alternator, regulator, ballast resistor, coil, electric choke, any other item powered off the engine run circuit
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