THIS MYSTERY HAS BEEN SOLVED! SEE THE CAUSE AND SOLUTION IN THIS POST, number 35: https://www.ford-trucks.com/forums/1...l#post15601996

THANK YOU to Everyone who provided very interesting input and theories as to what might explain the phenomenon, and to those who read the topic.

1987 F250 XLT Lariat Supercab, 6.9L non-turbo which was manufactured with the 7.3 style glow plug controller.

Feb. 2015: With BOTH negative battery cables disconnected, when the Ignition Key is turned to ON position, the whole system has power. The glow plug light (WTS) comes on and after-glow cycle worked normally (Except see further below). I noticed this while working on the upper steering column to replace a broken steering lock actuator rod. When I reinserted the ignition key lock-set and turned it to the ON position I heard the glow plug relay clicking in afterglow cycle. I confirmed that the negative cables were in fact disconnected and tucked away from the battery. The headlights could be switched on with the key in any position and be at full brightness. (That is normal if + and - battery cables are connected but not with the negative battery cables disconnected). Neither the hood, nor anything else was touching a negative battery terminal to complete a circuit.

I then disconnected the positive cables and finished that work. Next I replaced all of the glowplugs with new Beru ZD9's and repaired two glow plug wire ends. I reconnected the battery terminals and since everything SEEMED to be operating normally I just set aside this electrical phenomenon and forgot about it as an unsolved mystery.

I confirmed this electrical behavior again about 3 months later when I disconnected both negative battery cables before working under the truck. I wanted the truck in Neutral so I had to turn the Key ON to shift out of park into neutral and I left the key in the on position- negative battery terminals disconnected and tucked away off to the side- not touching anything.

After about 30-45 minutes I got back in the cab and the glow plug light (WTS) WAS ON!!! The headlights would also turn on full brightness with they Key in OFF position! I looked under the hood and both negative cables were disconnected- The hood was NOT touching a negative battery terminal on either occasion. I was afraid I had burnt out the glow plugs after 30-45 minutes under the truck but the new Beru ZD9s held up to whatever voltage they had received during that time.

With the negative cables re-connected the glow plugs are heating and cycling properly, EXCEPT that after replacing the glow plugs the GP controller solenoid stopped clicking during the after-glow cycle - I can see that the after-glow cycle is working for the normal amount of time by the voltage drop on the dash voltmeter so possibly something in the controller or controller solenoid has been damaged.

The system seems to be working normally otherwise and it's been like this since after I changed the glow plugs. But, changing the glow plugs had nothing to do with power to the system with the neg. battery cables disconnected since that first occurred before the new glow plugs (but then the controller solenoid WAS clicking as it should).

I've only driven the truck about 300 miles since then- a few 50-75 mile test runs after replacing common stuff a 28 year old IDI needs. It runs super great and does not even smoke! It has the Banks Power Pack air cleaner and larger exhaust with pyrometer (gauge doesn't work) and that better air intake and exhaust flow might be part of the reason it doesn't smoke.

Back to electrical: The truck can sit for 3 weeks with no apparent battery drain (no indications of such) and start right up on the first revolution.

Both batteries when completely disconnected from cables test out with the proper polarity and each read 12.43 volts

I completed electricians school including DC circuits and electronics 33 years ago focusing on the very technical and scientific stuff with straight A grades. I've never worked as an electrician though and that education is NOT automotive electrical. Still this unusual situation is a mystery to me.

After thinking this through for the past couple of months this is the only possible explanation I can come up with:

If I have a ground wire connected to the positive side of the fender well solenoid, could that possibly be providing a ground from a positive battery terminal to somehow complete the circuit when the key is on? I would think that this would cause a direct short circuit when the key is on and burn up something obvious but the only thing that doesn't seem to be working is the glow plug controller solenoid NOT clicking during after-glow cycle. (Maybe that is the "something obvious?") I have not seen nor smelled any indication of burnt wiring or components and everything else seems to be working fine. There is no drain on the batteries and the truck will start on the first revolution after sitting for 3 weeks.

I have a sketch of my wiring connections to the ignition solenoid on the passenger side fender well. There is only one heavy black wire on the ground side terminal that goes to ground, I believe at the starter. I've identified these solenoid wire connections with the Ford factory service manual schematics and they all look correct. The tracer colors on the wires are faded or discolored so a yellow tracer might look orange and an orange tracer might look brown so those differences might show in my sketch. I have to find my sketch and redo it to make it easier to read and then I will post it.

Meanwhile:

Question 1: What could possibly cause power to the system with both negative cables disconnected? It seems impossible for a circuit to be completed. I checked the batteries with a volt meter for voltage and polarity. It IS possible for a battery to reverse it's polarity under certain circumstances which might have lead to a possible explanation for this phenomenon but both batteries checked out fine at 12.43 volts and correct polarity. There is no extra battery hidden in the truck, I actually looked, LOL.

Question 2: The glow plug controller solenoid is no longer clicking during the after-glow cycle but the volt meter on the dash indicates that afterglow is working. Did I burn out something in the GP controller or controller solenoid so that now the after-glow cycling is actually a steady glow? I don't want to risk premature failure of these wonderful glow plugs from being on too long.

When the engine is up to running temperature after driving, I can restart it- the WTS still comes on for 10 seconds which I understand is normal with this 7.3 style GP controller and the afterglow (although not clicking) only lasts a few seconds if that much so the timer/temperature sensing must be working.

Now, to top it all off, I had both negative battery terminals disconnected yesterday and I checked to see if the electrical phenomenon persists and it does not. There is no power now to the ignition system nor to the headlights with the key in any position. I am wondering if a circuit in the glow plug controller that controls the intermittent voltage to the glow plugs during after-glow cycle has failed (no clicking) and instead I have constant voltage to the glow plugs during the after-glow and this failed function also ended the strange electrical phenomenon of having power with both negative cables disconnected ???

Due to a medical disability (which is recently improving) I have some significant cognitive and concentration impairments plus I'm taking morphine 3 times per day for pain which causes even MORE cognitive and concentration impairments. Otherwise I would normally be smart enough to figure this out but my brain doesn't work as well as it used to. Imagine being 1/3 of the way to full Alzheimer's disease (which is actually not my medical situation) and trying to figure this out. It just seems like Alzheimer's.

This also causes me to write long posts because I get lost and forget what I have written or not written and sometimes what I am writing about so I have to go back and look. (My excuses for writing lengthy posts)

THANKS for any comments on this mystery.

Fixnstuff. (or trying to)

1987 F250 XLT Lariat Super Cab 6.9L non-turbo C-6 transmission.

 

Do you have an aftermarket sound system? I wonder if there might be a capacitor somewhere providing unswitched power. Or maybe the truck once hosted a slide-in camper in the past, and there's a third battery tucked under the truck, in a box on the frame or something?

Re. the shift lock - you should NOT have to turn the key to RUN in order to shift out of Park. You should be able to turn the key to OFF (one click forward from LOCK) and the shifter should unlock.

 

whenever i do electrical work on any vehicle, i always disconnect the positive cables. never the negative.

 

Thank you madpogue. That is Very Smart Thinking!
Yes it has an aftermarket stereo/cd player with the worst wiring I have ever seen (by the previous owner) - I should have taken a picture of it to post on a humor website. It had a house lighting wall toggle switch hanging down to the metal floorboard (I have new carpet to put in) to turn it on and off with wires from it also on the floorboard to the big speakers in the back seat, all bare twisted connections, a wire under the accelerator pedal through the firewall, etc. I thought that I disconnected it. I removed the switch and I traced one wire under the hood near the drivers side battery to the radio but it had been disconnected and I assumed that was the power wire.

HOWEVER, I didn't pull the stereo out to see the wiring behind it and there is a small as yet unidentified wire to the positive side of the start solenoid which goes back toward the GP controller (I assumed it was to the GP controller) so I'll trace that today - maybe a ground to the back of the stereo (if connected by PO) or bare wires touching metal in the cab provide a ground to charge a capacitor. Intermittent ground from those bare wire splices could explain why the problem stopped. I'll get that sorted out today!

No battery, I've inspected the entire truck but thanks for the reminder, I have a factory tow harness with a trailer lighting circuit and 4 additional aftermarket 5 prong trailer connectors spliced into it behind the back bumper. I need to remove all of those, inspect the harness wiring and install a new 7 prong connector.

Just checked: On my 87 the steering wheel unlocks in the off position but the shift lever does not unlock until 'ON" eg; "RUN" position (added safety feature) and once it is shifted out of park the key can not be turned back to OFF position.

After I get the wiring cleaned up I'll see how the after-glow works because with no clicking of the solenoid, extended heating of the glow plugs worries me. The total time is maybe about 20 seconds at 'cold start' with ambient outdoor temps at 65-75 deg. F (18-24 C). I like the GP controller function (if it works correctly) but the WTS always stays on minimum 10 seconds even when the engine is completely warmed up and I don't like that. If that is normal (??) for the 7.3 style controller as I've read someone else state, then it is not well designed OR it is malfunctioning(??).

I have a very high quality push button switch I could install to bypass it and THAT may well be the best solution. A well labelled switch under the hood to switch the system from button to controller or back to button would be nice in case someone with no GP experience drives it, even with an LED indicator light by the button to tell that it is active with no power to the WTS light and vice versa when it is switched over to GP controller.

I'll figure that out and install the push button in a few months. I don't know yet if the GP controller needs to be replaced to operate correctly.

Wisconsin is a truly beautiful state, my ancestry on my mother's side goes way, way back in N. Wisconsin, Upper Peninsula Michigan and Ontario Province: French fur trade era and long before; Chippewa ancestry traced back to 1600s, French mixed in 1790s and later German mixed in around 1900.

When I lived in Minneapolis for 8 years until 1990 I spent considerable time in N. WI and Upper Peninsula MI doing family history research and always camping on those trips, sometimes with my motorcycle and a canoe on a trailer- other times just taking off from Minneapolis on my motorcycle to ride on the nice two lane highways through W. and N. Wisconsin. 'Easy Rider' in the N. Woodlands = Beautiful adventure!! No helmet required back then, just a headband and snoopy goggles or aviation sun glasses which was much more enjoyable without the helmet and a real sense of freedom as the classic movie 'Easy Rider' depicts. (except for the ending)

I hope to travel back there in a year or two with my truck and surely a smaller travel trailer, preferably 5th wheel (17-24 ft (5-7.3 m.). Mainly S. shore of Lake Superior and UP Michigan. I'll install an over-drive unit for the C-6 before travelling like that. I recently inherited some money from my very sweet aunt who owned a mostly forested farm in Waupaca, WI. Enough to completely restore this truck which I've intended to do since I bought it since it is such a nice truck. I won't receive this probably until the farm sells, surely by next year. Otherwise on my current low Social Security/disability income it would take years to fully restore it. That is where all of my extra money goes now and I'm always broke (=no $) and sometimes behind in bills but I'm very happy because restoring this truck is my current passion.

I also spent considerable time in Madison, WI in 1968-69 staying on W. Mifflin street near the corner of Broom street so I am familiar with the city, one of the best cities and states in the USA, I think. Late 60's; what an extraordinary era that was! Some like to remember and others want to forget.

Very nice truck you have, madpogue. Super Cabs are great for any long distance driving, even a few hours if you need a rest! Just pull off the road, put the back of the seat way down and sleep for awhile. Enough leg room for someone 7 ft. tall I think. Nice too if you have to pull off the road during a severe blizzard with extremely cold temps- I've had to do that several times! I kept very warm blankets ('comforters' like quilts) a warm hat to reduce body heat loss and a large candle in a jar to provide a little extra heat. I could tell some stories about being out on the highways during extreme blizzards and what happened but I deleted that part.

Anyhow, thank you for your reply madpogue!

Sorry for such a long post (excuses in last 2 paragraphs of my original post)
I'll try not to do that.

 

As far as the wait to start light. Ive noticed that with my 7.3s that unless the engine is already warmed up and the outside temp is over 100 degrees it will always use the glow plugs.

 

An Exorcist, or priest maybe in order...lol.

From what you've said, my thought almost went to a rogue capacitor, as madpogue mentioned, but with what's being powered up, most capacitors would drain out.

The electrical circuits for the vehicle 'should' be open due to having either both negatives, or positives disconnected; this will break the circle of current flow.

I cannot imagine the 'rat's nest' stereo stuff, but what I could see, is a battery hidden perhaps under the seats, or up in the dash, some sort of sealed 12 volt job, used for whatever reason to keep the memory going on the stereo.

Home grown electrical installations can get really creative, and I could totally see there being some sealed unit hiding out connected to the stereo.

Seriously beyond that, I've got no clue other than to start calling your rig, 'Christine', and perhaps sitting in her for long periods of time so she doesn't get too jealous

 

If it has big speakers and an aftermarket radio I wouldn't be surprised if they hack jobbed an amplifier and amplifier surge capacitor into the mix, they make some pretty big capacitors for this purpose. From what you described of the wiring it wouldn't surprise me if that little wire went to one...
People do crazy things with sound systems, my Mustang had a 0 sized ground cable running from the frame to the trunk and obvious previous modifications for the amp..... I don't even want to know what it was for.

 

If there are not any secondary power supplies, I'd second the need for an exorcist. Did you have any animals, were the animals going crazy?

I was working on a gasoline powered DC welder, in my garage, and the engine kept running when I tried to shut it down. My two dogs, 100 pound German shepherds, were about 20 feet away and got up from the ground and charged my area. The dogs were growling and barking in an aggressive attack and defensive manner. This made me think, perhaps, someone had walked into my garage from the rear entrance and was standing behind me and intending to cause me harm. With the hairs on the back of my neck standing up, I turned around to find no one. Perplexed, and with my body in chills, I went back to work, and pulled the main lead to the distributor, from the coil, after checking for positive power disconnect- the beast kept running and the dogs remained in offensive/defensive mode very close to me. Then, I thought maybe carbon was causing detonation I let the engine run and after about five minutes I pinched the gas line, which finally shut it down. When the engine shut down, my dogs acted all embarrassed and were very curious about the machine, which they had seen many times before, they had paid no attention to before.
Aside from demonic possession; opiates, pain, and memory and cognitive difficulties could indicate, perhaps, that you left the opposite terminal of each battery connected, providing 12V+ via one battery and 12V- by the other battery.
I am sure you know one should never operate machinery under such conditions, since next time you think something is removed it just might be your arm or leg.

Very inner-resting topic. Good luck and keep us posted if anything should happen again.

 

By chance, are your batteries the type that have both top posts AND side connections?

 

What's scary is if an entity from another dimension is inhabiting the truck, has claimed me as it's next meal and it's a slow eater...

The truck may have arrived from another dimension where there is another power source invisible to me and it's waiting to whisk me off into the stars. When I get to the top of the mountain I'll just keep on going, up and away. That will be a fun ride.

That is what I thought too, but that was an excellent lead (should be spelled 'leed' just as it is pronounced), an only explanation thus far beyond what I had checked and something that certainly needs to be ruled out.

twiggsV10 expands on that possibility with excellent knowledge, observation and logic which makes this possibility much more viable so see my reply to that when I get to it.

Consider also that it may have only been the WTS light coming on without any current draw from the glow plugs circuit, the headlights only turned on momentarily and this possible explanation is gaining ground.

Some sort of secret sealed hidden 12 volt thing? Under the seats or up in the dash? This is getting scary, like NSA/CIA/FBI SPOOKS Tracking Stuff!! Man, I got wires under the seats AND in the dash!
wAHT DO bOMBs wIRES LOOKs LiKe?

THAT DID IT! To heck with electrical phenomena, I am rippin' that SPOOKS stuff out of my Truck, and throw it all in the river!!!

I've been up all night and way too tired to answer another reply until later....

 

Disconnecting one positive and one negative renders the circuit open.

 

This all sounds so creppy. I hope my truck wont start doing thins now.

 

Our batteries are connected in parallel. Essentially, one terminal would be drawing off the positive charge of one battery and the chassis would be grounded though the negative of the other. The chemical energy, in one battery, is isolated in the battery case, so separating that isolation the width of a radiator makes no difference and forms the circuit.

 

Draw it out. With either terminal disconnected from each battery, the circuit is open.

 

Leaky battery grounding thru the tray??