Starting circuit challenge - intermittent fault SOLVED

[Finny]

Looking for ideas on an intermittient fault on my 1969 VF Valiant. Dart
Car will sometimes not turn over to start, at the same time no dash lights, no interior light and no headlights or tail lights.
This can happen quite quickly. Car can try to start, but turn key again and nothing. then later it will work again.
Interesting discovery is the the HORN works all the time. So power is getting to the horn but sometimes not reaching other electrical components.
I noticed in the wiring diagram that the horn is connected directly from the starter relay, so is one of the first items to get power.
Thought it might be an earth issue, but the horn works when everything else doesn't, so horn is still getting an earth.
And fuses must be OK because eventually I can get it to start again.
Anyone had this issue before or have an idea on what I can check?

 

[mrs49]

Looking for ideas on an intermittient fault on my 1969 VF Valiant. Dart
Car will sometimes not turn over to start, at the same time no dash lights, no interior light and no headlights or tail lights.
This can happen quite quickly. Car can try to start, but turn key again and nothing. then later it will work again.
Interesting discovery is the the HORN works all the time. So power is getting to the horn but sometimes not reaching other electrical components.
I noticed in the wiring diagram that the horn is connected directly from the starter relay, so is one of the first items to get power.
Thought it might be an earth issue, but the horn works when everything else doesn't, so horn is still getting an earth.
And fuses must be OK because eventually I can get it to start again.
Anyone had this issue before or have an idea on what I can check?

View attachment 1716206935

Check your ballast resistor, look for loose or broken wires, check ing. switch start-run contacts

 

[TrailBeast]

Looking for ideas on an intermittient fault on my 1969 VF Valiant. Dart
Car will sometimes not turn over to start, at the same time no dash lights, no interior light and no headlights or tail lights.
This can happen quite quickly. Car can try to start, but turn key again and nothing. then later it will work again.
Interesting discovery is the the HORN works all the time. So power is getting to the horn but sometimes not reaching other electrical components.
I noticed in the wiring diagram that the horn is connected directly from the starter relay, so is one of the first items to get power.
Thought it might be an earth issue, but the horn works when everything else doesn't, so horn is still getting an earth.
And fuses must be OK because eventually I can get it to start again.
Anyone had this issue before or have an idea on what I can check?

View attachment 1716206935

Ignition switch can do this, as can a failing connection at the amp meter.

 

[Murray]

There is no power to the horn. Contact at the steering wheel is a ground only.

 

[kiwigtx]

How are your ambient temperatures right now - or at least when trying to start the car?

Also check the age of your battery - I have a Falcon XR6 which did the same thing. Turned out to be a bad starter motor - full of carbon brush dust - drawing current even when the car was locked up and parked. Replaced the starter and it never happened again.

Check the battery terminals as well....if they are loose they do weird things at random times - again temperature is the key there.

 

[Dartswinger70]

how bout the cnnector on the column that always burns up gets hot? you wiggle that see what happens...its white multiple pins 10 mybe?

 

[jos51700]

Ditto start with battery condition, connection, and grounds.

 

[grjammer]

I had a similar problem, turned out to be a loose pop rivet holding an ignition switch contact to the plastic housing. Vibration made it intermittently not run. Replaced the ign switch and no more gremlin.

 

[Mattax]

Ballast resistor has nothing to do with starting.

Your Australian Valiant is not quite the same wiring as a '69 North American build.
But other than some insulation color and attachment locations, its works the same.

Car can try to start, but turn key again and nothing. then later it will work again.
Interesting discovery is the the HORN works all the time.

Assuming you've removed the battery terminals and made shure they are clean and snug....

Do you have a voltmeter?
Attach it to battery and place it where you can observe it while cranking the starter.

When the key is in Start, the ammeter (in your instrusment panel) should show about 5 amps discharge.
That's power going to the ignition, and to power the starter relay.
The voltmeter should show a slight drop in available voltage. When starter solenoid and starter engage the battery voltage should drop noticibly. But if goes below 9.5 Volts - the battery is weak.

So power is getting to the horn but sometimes not reaching other electrical components.

at the same time no dash lights, no interior light and no headlights or tail lights.

Interior lights, tail lights, and dome light are on a fused circuit.
The headlights are on a circuit breaker inside the headlight switch.
Assuming you're not seeing the ammeter indicate discharge (which would be a short).
Then there is a break or loose connection between the starter relay and the mainsplice.

Check the connection and wire from the starter relay to the fusible link, the fusible link itself, the connection through the firewall, and if those are all good, then the connections on the back of the ammeter.

I noticed in the wiring diagram that the horn is connected directly from the starter relay, so is one of the first items to get power

Yes. And to add to Murray's comment, the power goes to the horn relay. Inside the relay it connects to the wire going to the horn button. When the horn button contacts earth, then the relay's electromagnetic is powered and switches the relay on. The power now flowing through the horns goes to earth at the horns.

Thought it might be an earth issue, but the horn works when everything else doesn't, so horn is still getting an earth.

And fuses must be OK because eventually I can get it to start again.

The fusible link is a special 16 gage wire meant to fail before any of the 12 gage wires. It could be weakened, or any of the connections in that line could be loose, corroded or otherwise weakened.

Weak connection will still show voltage and allow some power through but choke when there are higher flows of electrons.

Based on your description, I'm leaning toward loose connection in the battery feed (starter relay to main splice) or damaged battery.

 

[Inertia]

The 2 commonest intermittent no-starts for service call.
1 - Dead battery or dirty Battery connection, - particularly the black deposit on the positive battery cable end.
2 - the stud and contact package in the starter solenoid, or less often worn brushes. (Replace starter these days).
All I got .
Good luck.

 

[Finny]

Thank you all for your ideas and input. Went armed with many of your ideas to test, but it ended up much easier than I expected.
Ambient tempurature in Brisbane is around 29C (85F) and Battery was fine, has been used in another vehicle and pumping out lots of power.
I had already check and cleaned and sanded all the battery and earth connections.
At the moment the auto choke isnt working, so I tried just turning it over with the key and it turned over for forever. I couldn't get it to fail.
Volts were fine, 12.6v and 11.5 under cranking, and ammeter was all measuring correctly. interior light stayed on and all electrical worked.
That was quite annoying, as it wasn't giving me a chance to fault find.
I looked for the fusible link (without success) so I decided to start working from the battery outward.
The lesson I had forgotten, was that when you acquire a new project, you need to learn what the previous owner/s have done.
Didn't have to go too far, and at the first junction saw a taped up wire. Once undone looks like a spade connection had been used at some point, it was clearly just connecting, rusted and poorly wound together. (you can see in the second photo)
Once seperated I had a "permanent" no power issue to starter lights and everything else. (Except the horn still worked)
Just that one wire. So I'll replace the faulty wire and do a proper connection.
Again really appreciate all the thoughts and ideas, looks like a good supportive and knowledgable forum, THANKS

 

[Ricks70Duster340]

Thank you all for your ideas and input. Went armed with many of your ideas to test, but it ended up much easier than I expected.
Ambient tempurature in Brisbane is around 29C (85F) and Battery was fine, has been used in another vehicle and pumping out lots of power.
I had already check and cleaned and sanded all the battery and earth connections.
At the moment the auto choke isnt working, so I tried just turning it over with the key and it turned over for forever. I couldn't get it to fail.
Volts were fine, 12.6v and 11.5 under cranking, and ammeter was all measuring correctly. interior light stayed on and all electrical worked.
That was quite annoying, as it wasn't giving me a chance to fault find.
I looked for the fusible link (without success) so I decided to start working from the battery outward.
The lesson I had forgotten, was that when you acquire a new project, you need to learn what the previous owner/s have done.
Didn't have to go too far, and at the first junction saw a taped up wire. Once undone looks like a spade connection had been used at some point, it was clearly just connecting, rusted and poorly wound together. (you can see in the second photo)
Once seperated I had a "permanent" no power issue to starter lights and everything else. (Except the horn still worked)
Just that one wire. So I'll replace the faulty wire and do a proper connection.
Again really appreciate all the thoughts and ideas, looks like a good supportive and knowledgable forum, THANKS

View attachment 1716207236

View attachment 1716207237

Yeah, that's pretty rough all right. That is what you can see too. Wonder how the under dash wiring looks?!

 

[Demonracer]

Yep, lesson learned. See what the PO has screwed up first. LOL

 

[jos51700]

"Before you fix it, make it right"

I'll never remember which Harley instructor told us that, but I've never forgotten it.

 

[Mattax]

Staying in that vein.

Based onthe Aus. Valiant Wiring diagram, this was probably the fusible link

A couple ways a fusible link can go.
The way they go quick is if an unprotected circuit gets shorted to ground.
This could be Joe fat finger reaching behind the instrument panel or removing the alternator with the battery disconnected and a wedding ring or spanner contacts the hot and ground (earth). Or in a blue moon something in the alternator output insulation fails and poof there goes the link.

BUT. it would not to follow that line all the way to the bulkhead and then inside the car.
Same on the alternator output line.
See that they and the main feeds to the key switch, the fuse box, and the headlight aren't chafing against sheet metal.

A somewhat common way to slowly deteriorate a fusible link is to run the battery down and then charge it from the alternator while driving down the road. That causes high charge rates for extended ( 10 minutes) periods of time. There will be heat damage at every connection between the alternator output and the battery.

Looking at the condition of the other wires I'm not saying either scenario I just mentioned is what happened. But if there is short lurking, best to know it before it bites ya.