510, Apparent soft short, expertise, and gerenal thoughts please

[BZT8FS]

Sorry, it's long.

1973 510, low miles (<55k), always been garaged, but not started for ~14 years.
I've built, repaired, modified, etc. many, many 510's, but it's been a while.

I've started working through cleanup on this car with my son and run into an issue that baffling us.

There are many smart folks on this forum, please weigh in. We've been chasing this for several weeks now.
Here it is:

There appears to be a soft short between the positive side of the ignition coil and the ground wire (both the coil ground and chassis ground).

It drops battery voltage about 1.2 volts from 12.5 to 11.3.

Since there's always a potential on the coil, breaking the points doesn't allow the field to collapse and spark.

The coil works fine (as does the backup) if I hook it to 12V on the bench and a spark plug on the secondary, so the coil isn't the issue.

If we disconnect the black/white wire from the fusible link by the fuse box, the soft short stops on the engine side but is present on the wire bundle going through the firewall under the dash.

We've one-by-one disconnected all of the connectors that we can get to under the dash, none remove the soft short.

There was some rodent chewing of the wiring harness under the hood, the section that runs under the radiator, which we've repaired.

All accessories operate correctly except: 1) left turn signal, 2) right front parking light (it's just the bulb), 3) wiper motor (it's out now, we'll rebuild it tomorrow, the switch works correctly at the connector, 12V present, washer fluid motor operates correctly), 4) The fog light I installed, 5) High beams are intermittent, the stalk switch isn't positive, moving it around makes the high beams come on.

I haven't measured the temp sensor and oil pressure senders yet.

 

Thoughts appreciated!

 

Thank you,

 

Paul

[datzenmike]

Disconnect the condenser (capacitor) beside the points in the distributor. Probably shorted internally.

 

 

If faulty just replace it. It will run without but this reduces arcing when the points open. Without it, the points will only last a hundred miles or so.

 

 

Smart.... ummm yeeees. Mostly experience and remembering.

[banzai510(hainz)]

14 hours ago, BZT8FS said:

We've one-by-one disconnected all of the connectors that we can get to under the dash, none remove the soft short.

which fuse removes the short?

 

I had a short in my 510 soemone added a Tach and wired to the cig lighter circut which is HOT all the time which drained the battery

Edited January 4 by banzai510(hainz)

[fiveoneO]

If you've disconnected the black/white wire from the fuse block and it still has a short, then I would fallow that wire under the dash and look for damage to it. I had a wire once from the fuse block to the ignition key sort out on the e-brake handle and it caused all kinds of problems. 

[BZT8FS]

Thank you all for the great suggestions.

datzenmike - yes, we've eliminated everything in the engine compartment (we believe).

Disconnecting the BW wire with the fusible link at the fuse box appears to identify this as after the fuse box and inside.

Tracing the wiring under the dash has been more difficult.

FiveoneO, is the e-brake wire you had trouble with one of those that does not go through a connector after the fuse box? Which/where is the e-brake switch? The brake light switch on the brake pedal operates the brake lights correctly.

banzai510(hainz), same question - is the wire to the cig lighter and/or tach one that does not go through a connector after the fuse box?
No fuse removes the short outside until the BW wire is disconnected - thus it appears that the BW wire or some portion of it goes through the firewall and is not fused.

We were looking at the turn signal/high/low beam switch on the steering column - it has a connector which we can disconnect - but there's also a single white wire that does not have a connector, it appears to be hard wired to somewhere.

Anyone have any ideas about that, it is stock - or do you think it might be something someone added on (like my 18 year old self 40 years ago and didn't document it)?

Following up on that idea, does anyone know which wires are not fused? Or should they all be and I've added in something that bypassed the fuse box?

RE: the engine compartment, the one bundle we've not traced and originated after the fuse box just before the main branch goes through the firewall runs over to the wiper motor bu there's another branch that goes down right in the middle above the tranny, we've thinking this is the connection for the backup switch?
Thanks again everyone!!

[datzenmike]

15 hours ago, BZT8FS said:

There appears to be a soft short between the positive side of the ignition coil and the ground wire (both the coil ground and chassis ground).

It drops battery voltage about 1.2 volts from 12.5 to 11.3.

Since there's always a potential on the coil, breaking the points doesn't allow the field to collapse and spark.

The coil works fine (as does the backup) if I hook it to 12V on the bench and a spark plug on the secondary, so the coil isn't the issue.

 

 

Even at 11.3 volts on the positive side current flows through the coil and is grounded on and off by the points. When they open the current stops and it sparks.

 

If the condenser has a small short to ground then current isn't completely stopped when the points open.

 

DISCONNECT THE CONDENSER. Would you rather trace wiring for a few days and then find that it's the condenser all along?

[banzai510(hainz)]

the BW wire should be the ignition fuse.pull that short should be goneI put a meter on the BW wire at the ballast resistor(remove the wire from ballast) and see if 12volt with key ON, then pull the fuse an see what you get.

Edited January 4 by banzai510(hainz)

[fiveoneO]

BZT8FS, the wire I had trouble with ran from the fuse block to the ignition switch(where you put the key in to start your car). That bundle of wires runs right next to the e-brake handle and at some point one of the wires had rubbed through on the e-brake handle and was grounding out. In my case it was easy to find, the wire was really burned up.

[BZT8FS]

Good morning folks, spent most of the day yesterday on the wiper motor. After completely disassembling the motor, cleaning it, greasing it, and reassembling, turns out it's fine. The internal wiper mechanism arms are frozen. The block where the attachment shaft for the wiper arms attach are frozen in place. Need to remove the circle clips and force the shafts out and clean them up.
Anyone have ideas on getting the bugger circle clip off? They've defied us so far.
Also looking for a couple of wiper sprayer nozzles, if anyone has any spares, we managed to destroy them while getting the wiper linkage out.

Also, what's the best method to share photos?
datzenmike - you're on the same track we were, spend several weeks on & off thinking about this. We have a spare distributor, spare coil & several spare condensers. No condenser shorts. Using an external power supply and distributor and coil on the bench, all is good, rotating the distributor(s) by hand delivers the expected spark. This issue is that, we thought as you suggest, opening the points allows the electrical field in the primary side of the coil to collapse and induce the spark from the secondary coil - is where the problem lies. The coil isn't actually grounded. The difference between the battery voltage the the voltage on the plus side of the coil (~1.2V) is enough to keep the primary field from collapsing quickly enough to induce a spark.
In this photo, one multimeter is connected directly to the battery terminals, the 2nd meter is connected to the plus & minus wires that go to the coil with the ignition in the "on" position (both wires are disconnected from the coil). Hmmm, I guess I don't know how to insert an image.
At any rate, there's a resistance between the positive side and the negative side, which goes away when the BW wire is disconnected at the fuse box.

banzai510(hainz), Thanks for the schematic, that's the one we've been using. If we disconnect the BW from the fuse box, the resistance between the plus coil wire and minus coil wire goes infinite, as needed and expected. I like your suggestion to monitor the resistance between the BW & ground & pull fuses. We did that and the resistance never goes away, so we're wondering what wires go through the firewall and aren't fused? We'll be looking at that closely today. Don't think it's the fuse box, it looks fine on top and underneath.

fiveoneO, We're starting to think it's something like this causing the issue, a wire that has the insulation rubbed through. What is the "e-brake"? I'm not familiar with that term?

Thanks everyone! Very helpful and making us think more.

Paul

[banzai510(hainz)]

Using a test light maybe better on BWwire.    then disconnect stuff to use if light fully out. Make sure you done have dome light clock to battery as give false reading

watch 1st 60secs

 

[BZT8FS]

Thank you, very helpful!! Back to the basics, it's been too long since I've been wrenching and I've forgotten the basics. I do in fact have a snapon test light that I used all the time. But the 1 watt 10 ohm resistor is the way to go, duhoh...

The kick in the pants I needed.

Thanks again.

[banzai510(hainz)]

1 hour ago, BZT8FS said:

But the 1 watt 10 ohm resistor is the way to go, duhoh...

with a 510 or early non electrical brain cars just the test light will work.

TEST light ON then pull the fuses till light goes out one that goes out is the suspect circut.But this is more for a battery drain.

 

I would just measure at the BW wire with IGNITION fused pulled for voltage(make sure key ON

Edited January 5 by banzai510(hainz)

[fiveoneO]

E-brake is the emergency brake/parking brake. Its the T handle to the right of the steering wheel mounted just under the dash.

[BZT8FS]

Thanks fiveoneO, I'm not asking the right question - what electrical switch or connection is associated with the e-brake? I guess I'm not aware of any, is there a switch somewhere on that assembly? Or was there nearby wire just in the area and getting aberrated by the action of the brake being pulled on/off?

 

banzai510(hainz), turns out that my son was paying attention the first time we pulled fuses, I was the fuse puller and wasn't, he was watching the meter. The 2nd fuse on the left side is the culprit, that says:

20 Flasher    Ign.

A  Luz

      Interm

Of course it makes sense that it's associated with the ignition. So I'll have to pinpoint which wires and functions on the schematic are associated with this fuse.

 

We're completed disassembly of the wiper arms, cleanup, reassembly, and installation. The wipers are now operating correctly. That grease they use turns into some rock hard almost epoxy concoction, it glues the shaft in place and is quite difficult to remove. After removing the retaining clip, I had to use the heat shrink gun to get the outer housing super hot to where it expanded enough to pull off the shaft. After that it was just cleanup and re-greasing.

 

I am now looking for a set of windshield wiper sprayers, "Sprayer Nozzles 27440-A2200", I'll post in the wanted section as well.

 

Sadly, Holiday break is coming to a close and the amount of time I'll have will be limited to weekends and some evenings, once my honey-do list is taken care of. We'd really hoped to get it running by the end of the holiday break, but at least with your assistance, we have a direction to correct the issue now. Hats off to the three of you (datzenmike, fiveoneO, & banzai510(hainz)) for jumping in immediately and giving me things to think about, explaining to you all helped me to clarify what we were doing and got us back on track. As we progress, I'll update what we find.

 

If anything else comes to mind, please let me know!

 

Thank you,

 

Paul

[datzenmike]

If the wire to the hand brake is rubbing a ground it will only turn the brake warning light on. That's all.

 

 

There's a switch on the hand brake (Yellow/Green stripe) and it turns on the red brake in the dash cluster. The ignition switch is LOCK... OFF.... ACC.... ON.... START. The brake warning light should light up when the ignition switch is rotated through ACC on the way to ON and START to show the driver that the bulb is not burned out. I think the '68 has a push button on the dash for testing the lamp.

[BZT8FS]

Let's see how well this works, a few photos. I'm not sure how the image quality will be.
The url isn't accepted when I use the insert image box. Do I need approval to use that, or is there a size limit?

https://imgbox.com/gallery/edit/AojxubuEk3/nrrnKUtTVuY6rTWo

[BZT8FS]

datzenmike, Thank you very helpful, as I sort through he schematic.
I have a custom dash and I don't recall if I retained that feature or not, I do see a red light.

[fiveoneO]

BZT8FS my problem wasn't the wire going to the e-brake, it was one of the wires going to the ignition switch. The bundle of wires runs next to the e-brake handle under the dash and it had rubbed through on the e-brake.

[BZT8FS]

Thanks fiveoneO, that's one area we're trying to figure out.

 

Anyone have any tips on how to post photos through the url box? I'm trying to use Imgbox and when I insert the url, the box goes pink, I don't know why.

 

https://imgbox.com/g/w2eYtpB1UT

 

We've tracked the issue to the solid green wire on the other side of the BW wire in the fuse box, but we've not been able to find where it is under the dash where it comes through the firewall. We've disconnected all of the immediate connectors on the inside of the firewall, but there appear to be some addition wires that do not go through connectors.

[BZT8FS]

Update:

 

Running power directly from the battery to the distributor/coil operates correctly as does the engine.
 

Running power through standard wiring, is problematic.

When a load is placed on the power to the car (i.e. power provided through the fusible link from the starter solenoid lug) the voltage to the coil (or to the wiper, etc.) drops from battery voltage to ~8V.

This happens if I turn on the high beams with the ignition switch in the "on" "start" position. Voltage at the battery remains constant (12.5V ish), doesn't budge at all. Turning on just the parking lights drops the voltage from ~12.5 to ~11.8, battery voltage constant.

We've been pulling fuses and found one fuse that shows the most voltage drop, labeled as the "park tail" fuse, 2nd one up on the right side of the fuse when looking in the engine compartment.

Looking at the schematic, all of the tail lights, rear side marker, backup and license plate lights, instrument panel gauge lights, all operate correctly when just the parking lights are on.

So, we're going cross-eyed looking at wire colors, disconnecting connectors and fuses without really identifying a specific issue.

One reminder that datzenmike provided in another post is that in this wiring system, everything is hot and activated by connecting to ground. Makes me think I've been missing something.

We'll regroup next weekend after all of this has had a chance to settle in.

Thank you all,

Bzt8fs

 

 

 

[datzenmike]

Are you measuring the voltage at the coil positive terminal? Don't forget in the ON position power from the ignition goes through a ballast or dropping resistor.

 

If you pull the small Black/Yellow stripe wire off the starter so it won't spin. Try measuring at the coil in the START position. That should read 12v same as the battery. When you let off of START and return to ON it will read a lower voltage.

 

Try running a jumper wire around the fusible link at the starter lug to eliminate it as the cause.

[BZT8FS]

Yes, measuring both in the "start" and "on" positions with the BY wire pulled off of the starter solenoid, same answer, ~8V.

 

Jumping the fusible link is a good idea, I'll give that a try next!

 

Have you seen those go bad?

[KELMO]

On 1/7/2024 at 2:18 PM, BZT8FS said:

 

 

 

On 1/7/2024 at 2:18 PM, BZT8FS said:

Anyone have any tips on how to post photos through the url box? I'm trying to use Imgbox and when I insert the url, the box goes pink, I don't know why.

Do they have a "BBC code " that you can copy and paste? I use Imgur and that is how I get pics posted on here.

[BZT8FS]

Hi KELMO, I've been using the url from imgbox, what is a "BBC code"? I'm not familiar with that term and don't see an option for it?

Thank you,

Paul

[BZT8FS]

Fusible Links

Are there any crossover part numbers, are similar/same ones used on other models?

I'm thinking that I need to replace both the one on the starter solenoid and the one at the fuse box.

Anyone have part numbers?

Thank you!