Headlights out and no idle - ground wire loose?

[MaddieCycle]

'86 KC with Z24. Suddenly lost my headlights (low and high beam), tail lights, and truck would not idle but otherwise ran fine as long as I kept my foot on the gas.  Turn, hazard, dome, dash lights all still worked.  All other electrical working fine and voltmeter reading 13V.  Then 10 minutes later the headlights returned and truck now idles fine.  Assuming there is a loose common ground for headlights and ECU or a solenoid on the carb.  Any thoughts?  I can't easily trace it at first glance on the wiring diagram.

Edited April 18, 2021 by MaddieCycle

[weldingrod]

2 hours ago, MaddieCycle said:

'86 KC with Z24. Suddenly lost my headlights (low and high beam), tail lights, and truck would not idle but otherwise ran fine as long as I kept my foot on the gas.  Turn, hazard, dome, dash lights all still worked.  All other electrical working fine and voltmeter reading 13V.  Then 10 minutes later the headlights returned and truck now idles fine.  Assuming there is a loose common ground for headlights and ECU or a solenoid on the carb.  Any thoughts?  I can't easily trace it at first glance on the wiring diagram.

My Dad always told me if something won't start then check the gas tank. In other words, check the obvious first, it will also be cheapest.  Maybe loose or corroded fuse or loose or corroded wire at the fuse box is the first place I would look. Next would be light switch.

[datzenmike]

 Headlights have their own dedicated fusible link and L&R fuse. Get a $3 12v test lamp and check both terminals on the last two fuses #15/16 on the far right hand side of the fuse box.

 

If you have power look at the headlights switch. Take the two part clam shell off the steering column and you may be able to use a spray can of electrical contact cleaner on it. If not remove the steering wheel and you can remove it and the attached wiper switch.

 

If you don't have power, find the fusible links, attached to the positive battery cable at the battery. They are about 4" long and have plastic plugs on the end so that can be removed and replaced. It's a green one (but there are 2 of them) It may appear fine on the outside but the wire is melted inside. Check for 12v at both ends.

 

If broken inside it very possible that it might touch and make contact again. Turn headlights on and wiggle the wires.

[MaddieCycle]

Well these suggestions are all of the obvious ones. Haven't had time to go through things yet.  However the real question is why did I loose my idle at the same time, and then when the lights came back on the idle returned. To me that says a problem on the grounding side, or otherwise a short in the system somewhere.  

[Charlie69]

I have been having lots of electrical gremlins for several years on my 86 720 king cab.  What I found was the negative battery cable was connected to the fender well but the end that connects to the engine was not connected.  connected the engine ground and so far every thing is working.

[datzenmike]

11 hours ago, MaddieCycle said:

Well these suggestions are all of the obvious ones. Haven't had time to go through things yet.  However the real question is why did I loose my idle at the same time, and then when the lights came back on the idle returned. To me that says a problem on the grounding side, or otherwise a short in the system somewhere.  

 

A short is an unwanted 'short cut' for power to get to ground... it would blow a fuse. The ground cable bolts to the intake so unlikely it's a lack of ground on the engine or the starter and the EI ignition would not work. However this is an ECC system and the ground for the idle cut comes from the body as well as a ground return for the headlights.

 

The common thing here is the body sheet metal ground connected to the negative ground cable. On some trucks the ground cable is bolted physically to the body and then bolted to the intake. It is probably near the battery box, just follow the negative cable.

 

 

[MaddieCycle]

Great, will check there.  I find the electrical system in these 720s to be designed to invite gremlins.  Sometimes shorts don't blow fuses, they create alternate ground paths, leak currents, or backfeed currents that can wreak all kinds of havoc.  Strangely, this problem did not occur again on my trip, but the next day I had two incidents where I turned the key, heard the solenoid click, saw the voltage meter drop, but the starter did not turn over. A few tries of this and it started right up with a strong cranking.  Something is loose in there.  Or, my starter could be fixing to die and that is a separate problem.  I guess if I get stranded I'll bump start it and come home.

[datzenmike]

 

 

What you are describing is a voltage leak. A short is an unusual connection in an electrical circuit between two places that should be at different voltages and forces them to be the same. Current flow is maximized and heat and fire is a real threat unless there is current limiting provided by a fuse or the short itself burns out. 

 

 

Clean the battery posts and clamps and tighten them. 

[Charlie69]

Check the alternator wiring is tight and clean.

[banzai510(hainz)]

check the battery cables for cracks and tightness, reseat the fuses

[MaddieCycle]

I snooped around and found the relay above the fuse box that is next to the blower motor relay was clicking only intermittently when I turned on the headlight switch. I believe this is a headlight relay. In any case, I had just 2 weeks ago replaced the blower motor and when tracing that problem had removed the blower motor relay. I assumed I'd disturbed something with this other relay in the process so I took it out and cleaned things up and now none of the problems have happened again. 🤷‍♀️

[MaddieCycle]

Well this problem presented itself again and so I went fishing again and found I was able to reproduce it by jiggling the fusible link connector at the battery.  So there lies the problem and explains why seemingly unrelated things start going on the fritz at the same time.  I will dive in there to figure out exactly what is going on and fix it.

[Charlie69]

Picture of your fusible link I might have a used replacement.

Or

When I get ambitious I replace the fusible links with these. I get these out of the Nissan Quest vans do not remember what years.  They are on a bracket connected to the battery tray.  When ever I come across one in a wrecking yard I buy them.  I also get the battery tray and relay boxes that are bracketed to the battery tray.

 

 

 

This is the quest battery tray customized to fit my 66 520.

 

 

Edited May 20, 2021 by Charlie69

[MaddieCycle]

So I've got the fusible links cleaned up.

 

The starter problem continues.  Sometimes I turn the key and just get the click of the solenoid.  If I turn the key a few times like this, eventually the starter engages.  Battery cranks strong and truck starts right up.  Assuming I either have a power supply issue to the solenoid, and the solenoid is moving enough to click but not enough to engage fully, or that the solenoid itself is on its way out. I am inclined to just replace the solenoid, they are still available new from Nissan, OEM Hitachi, for $94.  The starter motor itself seems fine. I would assume that the starter either works or doesn't, I can't think of something inside the starter motor itself that would make it just sometimes not turn at all and other times work fine.

[Charlie69]

I had a similar problem with my 86 720 and it turned out the the ignition switch on the column was worn out.  Replaced it and have not had a problem since, that was ten years ago.

[NC85ST]

I had a similar problem and I installed a relay between the solenoid and ignition switch. Haven’t had a problem since.

[datzenmike]

17 hours ago, MaddieCycle said:

So I've got the fusible links cleaned up.

 

The starter problem continues.  Sometimes I turn the key and just get the click of the solenoid.  If I turn the key a few times like this, eventually the starter engages.  Battery cranks strong and truck starts right up.  Assuming I either have a power supply issue to the solenoid, and the solenoid is moving enough to click but not enough to engage fully, or that the solenoid itself is on its way out. I am inclined to just replace the solenoid, they are still available new from Nissan, OEM Hitachi, for $94.  The starter motor itself seems fine. I would assume that the starter either works or doesn't, I can't think of something inside the starter motor itself that would make it just sometimes not turn at all and other times work fine.

 

Don't throw parts at it. Carefully... connect a jumper wire to the positive terminal of the battery. Put truck OUT of gear. Touch the solenoid terminal that has the start signal from the ignition switch.

 

1/ If it continues to click the odd time then possibly the solenoid is at fault.

 

2/ If it starts every time without the false click then the signal from the ignition switch is weak. (long wire run, thin gauge wire, old wire causing a voltage drop. Could be the ignition switch)  See the post below. It's called a hot start relay and saves you buying a new starter or solenoid that doesn't fix the problem.

 

28 minutes ago, NC85ST said:

I had a similar problem and I installed a relay between the solenoid and ignition switch. Haven’t had a problem since.

 

[MaddieCycle]

Yes Mike I did all of this.  Direct jumper to the battery and it cranked every time without delay.  Put the wire back on after scrubbing the terminal and cleaning things up and I have some of the delays again, though much shorter.  For now, I am just going to sit on it.  If it gets worse, I'll go with a hot start.  If I get stuck somewhere I'll just jumper it to the battery, drive home, and do the hot start.

[Charlie69]

Try replacing your ignition switch or take and jumper the plug at the switch and see if the starter engages every time.  Wiring problems are a process of elimination.  Start at the 2 farthest points and work from one end to the other.  Starting in the middle makes more work of it.

Edited May 30, 2021 by Charlie69

[MaddieCycle]

On 5/30/2021 at 4:29 AM, Charlie69 said:

Try replacing your ignition switch or take and jumper the plug at the switch and see if the starter engages every time.  Wiring problems are a process of elimination.  Start at the 2 farthest points and work from one end to the other.  Starting in the middle makes more work of it.

Seems easier to just do nothing now and then do a hot start bypass if it becomes problematic, than dealing with the ignition switch. I've been in the steering column before to deal with the 4 way flasher nightmare, I feel like messing around in there will be a cascade of 35 year old equipment problems. 

[Charlie69]

Pull the plug off of the ignition switch and using a jumper wire jump the 2 terminals for power and starter.  If the starter engages every time then it is the ignition switch.  This is about as simple as it gets.

[MaddieCycle]

Pulled the ignition switch and tried hotwiring from the switch harness. Same problem. But, again no difficulty at all when jumping right to the solenoid from the battery.  So now I can reproduce the problem even bypassing the ignition switch, but it still does not reproduce with a direct jump.  I think I am going to toss in the towel, I have no interest in tracing this down. Going to grab an 85/87 type relay and make a hot start bypass.

[datzenmike]

From battery to ignition switch is probably close to 3 meters and about that much back out to the starter. Lets round down to about 15 feet. At least, plus numerous plug-in and bulkhead connections. Add to that narrow gauge wire that is 35 years old. There is bound to be a voltage drop. 

[MaddieCycle]

44 minutes ago, datzenmike said:

From battery to ignition switch is probably close to 3 meters and about that much back out to the starter. Lets round down to about 15 feet. At least, plus numerous plug-in and bulkhead connections. Add to that narrow gauge wire that is 35 years old. There is bound to be a voltage drop. 

Agreed. When I checked the open circuit voltage,  it does hit 12v.  But I am certain that once the solenoid load is on that circuit there is a big drop.

[datzenmike]

I had 7 or 8v on my 710. This was the start signal from the ignition switch. Usually there was 3 or 4 tries with the key, with a click then it would engage. I had over a dozen used starters so I threw one on and was very surprised to find this did not help. Used an old spanner and jumped from the positive cable on the starter to the starter solenoid and it worked every time. That when it dawned on me what the real problem was. Not surprisingly my second 710 was the same.