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

[BZT8FS]

Thank you all for taking the time to read through this!

Apologies, I'm not able to work through any diagnostics during the week, only weekends.

I can answer most of the suggestions.

We're using the DAMB Productions 1997 Rev E 510 Sedan w/Manual transmission schematic for reference.

 

Battery: 3 months old. External charger says it's fully charged. Also supplemented it with a fully charged Clore JNC770B 1700 amp jump starter battery pack. The external battery pack makes no difference. The voltage at the battery terminals does not droop either way under any conditions other than actually running the starter, and then only nominally, like 0.2V to ~12.4V.

 

Regulator:  Has been taken completely off, grounds and connector connections cleaned and reassembled. Multimeter measures 0.0 Ohms between the regulator ground and the battery negative terminal.

 

Coil Voltage: The BW wire disconnected from the ballast resistor and the BG wire disconnected from the + Coil. When in start (starter solenoid disconnected), contact #5 in the ignition switch connects. ~11.6V without any accessories, 8.5V ish if any accessories are turned on. Battery voltage does not change, nominally like 12.6V. No change between low beam or high beams, same low voltage situation.

Same result in the On position and measured on the disconnected BW wire from ignition switch contact #2 that goes to the ballast resistor.

 

Connectors: We disconnected and cleaned all connectors that we can get to. I don't think we've located the connector for the taillights or the heater fan (but it operates correctly), I'm not sure where those are under the dash.

 

Also, I have a custom dash cluster so the normal round dash cluster connector doesn't exist, those connections are hardwired to the replacement gauges. They all light correctly when the parking lights are turned on and the replacement dash indicator lights all turn on correctly. They're all Stewart Warner gauges.

I'm not sure if the white and red wires that go separately through the firewall next to the main bundle with their own opening in the rubber gasket go through a connector anywhere inside.

Alright, I hope this makes sense.

[datzenmike]

1 hour ago, BZT8FS said:

 

Coil Voltage: The BW wire disconnected from the ballast resistor and the BG wire disconnected from the + Coil. When in start (starter solenoid disconnected), contact #5 in the ignition switch connects. ~11.6V without any accessories, 8.5V ish if any accessories are turned on. Battery voltage does not change, nominally like 12.6V. No change between low beam or high beams, same low voltage situation.

Same result in the On position and measured on the disconnected BW wire from ignition switch contact #2 that goes to the ballast resistor.

 

 

 

The power from the ignition switch is totally wrong. It should read 12v on the #5 in ON and START. To eliminate the ignition switch check the #3 terminal wire (Black/Yellow stripe) if it reads battery in all positions then the ignition switch is faulty.

[BZT8FS]

On the referenced schematic contact #3, BY only connects in start position as it's shown going to the starter solenoid.

Wouldn't the suggestion be to verify voltage on the WR #1 connection that brings power to the switch is 12V in all positions?

Perhaps there's a different schematic?

This is a good way to look at it and verify.

Thank you!

[datzenmike]

Yes the power in from the fusible link. Yes! wrong wire.

 

White/Red wire. Should hold at battery voltage in all ignition switch positions. If it does then what's being sent to the coil is at fault. It would seem the ignition switch is bad.

 

If the White/Red also drops under load then the fusible link is at fault. I thought earlier I suggested jumpering around the link to see if that changed anything.

[BZT8FS]

You did suggest jumping the fusible link, I could not get the connectors apart to save me so I pulled all the fuses in the fuse box and measured resistance across the fusible link as i can get the probe tip into the contacts (it was zero, to the resolution of my multimeter), however good point if power sags on WR at the ignition switch, that is where the fault lies.

I hadn't thought to check voltage on the switch, that's a very good suggestion.

[datzenmike]

You don't have to remove, just have someone hold a wire around the link from the starter lug to the fuse box. If things improve then the link is faulty.

 

Measuring the voltage on the White/Red AT the fuse box will also work. If it remains steady at 12v while switching the ignition through off and on then has to be the switch.

 

We're getting close.

[BZT8FS]

Continued troubleshooting. I thought we were on to something here datzenmike, unfortunately doesn't look that way. Nothing points to the ignition switch or the fusible link:
Here's what we've diagnosed so far.
Battery voltage 12.6V (stays constant except when high beams on, then down slightly 12.56V).
1) Battery connected, nothing on, key out a) White/red wire on ignition switch contact #1; V=12.2 (Using multimeter pin probe into wire right at connector on ignition switch)
2) Battery connected, nothing on, key out, flasher fuse pulled a) White/red wire on ignition switch contact #1; V=12.6, same as at battery

3) Battery connected, key "ON" position, flasher fuse pulled 1) White/red wire on ignition switch contact #1 & BW wire to ballast resistor (wire disconnected from resistor); V=12.6, same as at battery (same on BL disconnected coil wire when in "Start", (solenoid disconnected)).

4) Battery connected, key "ACC" position, flasher fuse in 1) White/red wire on ignition switch contact #1 12.2V; a) pull headlight switch to parking lights (1st position) 11.53V, b) pull headlights on (low beams) 11.23V, c) pull high beams on 8.8V
5) Battery connected, key "ACC" position, flasher fuse in 1) White/red wire on ignition switch contact #1 12.2V; wipers on ranges from 11.23V - 12.00V as wipers cycle. Pull flasher fuse voltage goes up ~0.5V (11.73V-12.2V); pull on high beams w/wipers on, contact #1 ~8.3V

6) In condition 5, headlights on low beam, 0.3V appears on coil wires, when high beams on 0.6V appears on coil wires  (goes back to zero when flasher fuse pulled)

Disconnect voltage regulator connector, no change to the above.
Disconnect WR wire on alternator, no change to the above.
With regulator conector and alternator WR wire still disconnected:
Jump from battery positive terminal on starter solenoid (accidentally touch other end to ground and weld alligator clip to ground and burn wire off of alligator clip, arrrrgh, get new jumper) to white wire that changes to White/Red to contact #1 on ignition switch, no change to above voltages.
Disconnect battery positive terminal cable. Jump from battery positive terminal directly to white wire, bypassing fusible link, no change to above voltages

Tried multimeter ground to car body, to engine block, and directly onto the negative battery terminal (and all at the same time), no change

 (voltage on both coil wires match whatever voltage is on contact #1, when key is "ON" or "Start")

The puzzle continues....

[datzenmike]

Try removing the wires from the coil positive terminals. Then check voltage in ON and with and without headlights.

[BZT8FS]

All coil voltages shown are at the disconnected wires; wire to ballast disconnected and the coil ballast bypass disconnected.

I'm at a loss to understand how anything from the flasher circuit would be putting a small voltage on those wires. The flashers operate correctly and there does not appears to be any electrical path to those wires from the flasher circuit on the schematic.

Next step I'm going to measure the current flow across the flasher circuit with battery connected and everything off.

But that will have to wait until next weekend, we're getting massive wind & rain here today.

[datzenmike]

Turn signal flasher? That has to be turned on by the ignition switch. The hazard flasher is on at all times. It requires the hazard switch or the turn signal switch to be activated to provide a path to ground through the lights.

[BZT8FS]

The fuse that I remove that makes things better (we're removed each, one at a time to find any improvement) is for the emergency flasher (i.e. hazard lights) and the hazard lights operate correctly.
The turn signals do operate correctly when the ignition is "ON" - but to your point, we're not activated them during any of our testing, I'll add that as well.

[datzenmike]

So volts at the disconnected ignition coil in ON is not battery?

[BZT8FS]

When "ON" & 3rd fuse down on the left labeled "Flasher" is pulled and nothing else is on, then same as battery.

When fuse is in then no.

Regardless of fuse position, if lights, low beam, high beam, or wipers are on, then does not match battery.

[BZT8FS]

 We have SMOKE!

Haven't had a lot of time the last two weeks, but secured all wiring that I had apart for diagnosis and thought I'd give it a go to start the engine using my external thumb switch (Snapon) between the solenoid BW wire terminal and battery positive at the solenoid. When we tested this config a couple of weeks ago, the voltage at the coil didn't droop much when running the starter this way.

So with key in the "On" position I started to crank and the green fusible link wire by the fuse box started smoking, so I immediately pulled the positive battery cable. Couldn't see exactly where the smoke was coming from but when I measured temperatures in the area with my laser temp meter, the connector on the engine side between the BW wire and fusible link wire was the hottest. This is the connection that I could not get apart, the connection on the fuse box side come apart as expected. I don't want to use pliers to pull it apart until I have a replacement fusible link in hand.
This BW wire after the fusible link goes into the the fuse labeled "Flasher & IGN" (2nd one up on the left)- the one with the green wire going through the firewall that we previously identified as the one that appears to have the soft short we've been chasing.
I pulled the fuse and put an ammeter in circuit in place of the fuse. With the key out & off just attaching the positive battery terminal I get 1 amp flowing across that fuse station. Nothing is on. I'd expect no current. We tried having the key in "ACC" & "On" and turning on headlights, high & low beam, wipers slow & fast, etc. The highest current we saw was around 2 amps. No idea why the fusible link started smoking.
I did find something puzzling that maybe you're run across. I've been using the very nice "DAMB Productions 1997 Rev E." schematic as a reference. I started looking at the "2001 Mitchell Repair Information company" 1973 Datsun 510 schematic because it specifically says "1973". I find one difference between these two schematics in this particular area. It shows the fusible link going to the BW wire but the a little further on it shows "Resistance Wire" with BW on one side and the other side coming out as BL.

Anyone run into this before? Any idea what or where "resistance wire" is? Is that an error or something real?
Thanks Everyone, more later.
For those of you with a three day weekend, enjoy!

 

[datzenmike]

With ignition OFF there should be no current flow except if you have an electric clock and it would barely measure on a meter.

 

 

 

With the meter registering 1 amp start pulling fuses till it stops... that will be the circuit with a draw.

[banzai510(hainz)]

Cant really see why this would smoke at this place. its just the hot start wire

Edited February 19 by banzai510(hainz)

[datzenmike]

Poor connection? not soldered or soldered incorrectly. ANY resistance will heat up, depending on the resistance and current flow, but will generate heat. This is how a toaster works.

[BZT8FS]

Thanks! I appreciate the inputs, when we're in the middle of it we don't think things through real well.

The only scenario that makes sense to get the fusible link smoking is if somehow in the "On" position the BL wire from the "Start" position is shorted to ground, that's the only way I can see that happening - raises suspicion that the ignition switch is not well.

 

To your point Datzenmike, there should not be any current flow across the flasher fuse when everything is off.

So we started measuring some resistances, with the fusible link disconnected measuring from the BW wire going into the fuse box and to ground at the battery, we get ~10 Ohms (should be zero).

Then things get even odder. pulling on the parking lights, resistance drops to ~9 ohms, pulling on the headlights, it drops even further to ~1.2 Ohms. Then in that condition if the right turn signal level is activated the resistance goes up to ~9 Ohms, if the left turn signal is activated it goes to 6.7 Ohms. So something is not right.

 

We haven't been very methodical about this and have spent a lot of time chasing things around, so next time we're going to measure the resistance of each of the wires between the fuse box and the switches (Ignition, Headlight, Turn signals), then we should be able to pinpoint which one has the high resistance and correct it.

 

Do you know if there's a body ground for the wiring harness under the dash somewhere? If so, where is it?

 

Many thanks!

 

[BZT8FS]

Alright, delayed update. Had some time last weekend and a few hours this weekend.

Zeroing in on the issue. We've verified that the resistance of most of the wires between the fuse box and their destinations under the dash have essentially zero resistance, as you'd expect with copper wires.

We've buzzed out most of the wires under the dash now.

Remember that we'd identified the green wire from the fuse box coming out of the "Flasher" fuse 2nd one up on the left as having high resistance and 1 amp across it with battery hooked up, noting turned on, and the key out?

The green wire goes a couple of places and ends up over at the turn signal switch on the steering column and is the single connection plug next to the 4-pin plug.

It goes under the dash and branches to the hazard flasher switch, to the dash instrument panel, & clutch switch. When the hazard switch is in the off position it routes the green wire through the turn signal flasher and then over to the single green wire connection on the steering column turn signal switch.

With the battery disconnected and key off, if the hazard switch is pulled on, that branch going to the turn signal flasher and steering column switch is isolated.

This branch has high resistance.

Disconnecting the single green plug and 4-pin plug to the turn signal switch.

Measure resistance between the green wire and the right turn signal wire (#4, Green/Black) with the right turn signal "on" there's nominally zero resistance.

Now repeat for the left turn signal - Ah-Ha! This is where the issue is.

Measuring between the green wire and the left turn signal wire with the left turn signal "on", resistance is about ~30 Ohms.

Tried spraying contact cleaner, it helped a small bit but really didn't change the issue, can't really get the spray inside.

Next I need to measure between the green wire and ground - I suspect there's an issue in the switch case.

I was running out of time and didn't finish up all of the diagnostics I wanted to but it appears that the "soft short" is in the turn signal switch.

I'm pretty sure these are no longer available to purchase so I'd have to take it apart and see if I can repair whatever is the cause.

Does anyone have a photo of the turn signal switch taken apart?

[nathan.is.an.idiot12312]

hey almost positive you could probably find a switch for a 210 thats a few years younger, and retrofit it, they still make them. i think they were relatively universal for the time period but idk you might need to probe around and make a new terminal for it. not hard at all. hope this helped. 

 

mike, let me know if im wrong though lol

[banzai510(hainz)]

On 1/3/2024 at 7:08 PM, 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.

this was your intial write up.

So if you disconnected the turn signal connector will the car run? Now.

 

as for the 30ohms thing are you measuring thru the flasher unit? as this is a bimetal element that bends when current flows throw it.

 

3 pages I forgot the orginal proplem now of what exactly is the proplem as we in the turn signals circut. (just pull the fuse on them) to isolate if car runs or not. Since we was looking at ignition proplem on page 1

Edited March 4 by banzai510(hainz)

[nathan.is.an.idiot12312]

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heres a factory switch for your car, really expensive right?

 

now check these out, 

 

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[nathan.is.an.idiot12312]

or you could just hotwire the terminal for the time being lol

[datzenmike]

You'll have to pop the steering wheel off, split the plastic clam shell around the steering column to get at the turn signal/hi/low headlight switch. If there's a problem it should be obvious. 30 ohm is about the resistance through a turn signal lamp.

 

My 620 switch failed once. Turned out the blob of solder became detached. I simply soldered it back in place but it took an hour to figure out how the damned thing was supposed to work. On the 620 the first movement of the turn signal lever disconnects the brake signal from that side, next the flasher is connected to that side lamps providing a path to ground and the flasher begins to flash. Now this is for a vehicle that shares both flasher and brake light bulbs.

[Stoffregen Motorsports]

47 minutes ago, datzenmike said:

 Turned out the blob of solder became detached. I simply soldered it back in place but it took an hour to figure out how the damned thing was supposed to work.

I've seen this more than once.

 

Taking the switch apart is not difficult, but be careful you don't loose a spring or one of the balls. Ok, I've never seen inside this particular switch, so I'm only guessing, but most of them from this era are very similar. Once you get it apart, you can clean the contacts and check that all points of contact are making their connections. Lube it up with vaseline or even WD40 if you don't have any electrical grease.

 

But as Mike said, check closely for broken wires or other broken things in there. Even a bent spring contact.