Hi, Guys! Happy New Year! So, I took my 1957 F600 out for a drive the other day and everything went just fine until I tried to start the truck after it had been sitting for about 15 minutes. The first two start attempts resulted in the illumination of the GEN and OIL warning lights but no crank of the engine. Subsequent attempts produced no results whatsoever; the truck seems to be electrically "dead". Here are the things I have been able to test or verify so far: The battery is new and charged. The positive and negative cables are clean and tight. I can measure 12 volts at the input side of the starter relay. The lights and horn do not work with the key in the off or on position like they used to. When I turn the key there is no clicking from the relay. I do NOT get 12 volts at the IGN terminal of the ignition switch regardless of switch position. None of the "jumper" test/troubleshooting procedures in the shop manual result in any cranking or warning light illumination. I can measure continuity between the positive wire attached to the resistor and the terminal of the wire attached to the IGN terminal of the ignition switch. The resistance across the resistor, terminal to terminal, is 3.5 ohms. I do NOT get 12 volts at the BAT terminal of the headlight switch regardless of ignition switch position. The electrical system is mostly original and complete but there are definitely some things that do NOT correspond to the outstanding wiring diagram I got from Classic Car Wiring. I am currently suspicious of the wire that goes from the small "S" (forward) terminal of the starter relay to the positive side of the resistor because it seems as though I should be able to read continuity there and I cannot. I'm sure I am missing some critical pieces to this puzzle but I look forward to hearing what you folks will ask and any assistance you may be able to provide!!

 

Is there a fusible link in the wiring harness? If so, I bet it's toast.

 

Oh, and by the way, a high-resistance bad spot in the wiring harness may still pass enough voltage to read 12V on a meter when there's no load, but drop right to zero when loaded. While checking around for voltage, turn the headlights on or some other load that used to work and now doesn't.

 

Thanks for the replies, krewat! So, here's what I did today: I made a jumper so that I could measure the resistance from the battery input side of the solenoid to the battery terminal on the lights switch:0.5 ohms ( that includes the resistance in the jumper which was about 6 feet long). I then hooked up the battery and I was able to measure 12 volts at the same light switch terminal. The wiring then goes to the "BAT" terminal of the ignition switch. I could also measure 12 volts there but the wire had been damaged and the turn signals had been spliced in that run so I made a new wire and removed the splice. Now, here is the goofy part that I can't figure out: I am getting this 12 volts at the "BAT" terminal with the key in the "OFF" position, which makes sense. This is how you are able to turn on your lights and honk your horn when the key is "OFF". When I turn the key to either the "ACC" or the "ON" position my 12 volts goes away. Also, if I turn the key to the "START" position I do not get voltage at the STARTER terminal of the ignition switch. I can get the same result if I connect up to the "BAT" terminal on the light switch as in my earlier testing. The ignition switch itself (out of the truck) gives me about 1/2 of an ohm between terminals as it should depending on switch position. Basically, at this point I cannot get a load put on the system because nothing will come on regardless of which position the ignition switch is in. I even tried using my jumper wire and running straight from the battery side of the solenoid to the "BAT" terminal of the headlight switch, bypassing all the trucks wiring and still, nothing! I am dazed and confused and I have decided to call it a night and have a beer...!

 

Oh, I almost forgot! In all of that testing the lights switch and the ignition switch were hanging below the dashboard but I made sure to run a jumper from the shell or frame of each switch to chassis ground to simulate them being installed...

 

Maybe try this rather simplistic approach. Get a test light and attach a 10 foot jumper wire to it. Turn the headlight switch on. Attach jumper to + cable end on battery. Light should light when touched to - battery cable on battery. If not you have a bad battery cable connection. Now follow the positive power feed with the probe. Touch the stater relay, ignition switch, fuse box feed etc. When the light lights you are on the other side of the open circuit. Work back toward the battery to find it. Do the same thing with the negitive side if necessary.

 

Did you check the grounds? A missing ground can cause voltage to feed through all sorts of other things. There should be ground going directly to the engine, and then as stock in the 70's from the back of the intake to the cab. Make sure all these grounds are solid.

 

Negative battery connection. Probe engine body and maybe the frame. What did you find?Most likely one of the points Krewat suggested.

 

Hello everybody! Thank you to all who replied with suggestions and advice! I am VERY happy to report that the problem has been solved! It turned out to be a bad ground where the negative cable from the battery was connected to one of the bolts that are used to attach the battery tray! Ten wheeler and krewat, MASSIVE kudos to you fellows!! You guys nailed it! A good friend of mine was listening to me recount all the messing around I had been doing and suggested that before going any further that I check and verify that the ground path for the battery was sound. Literally 5 minutes with a test light proved out his theory and now my truck is running again! I was hesitant to believe that this was where the problem would be found because I had JUST had all of that stuff apart to put a new battery tray into the truck. I thought "how could that be the problem when I was just working there and everything was operating normally when I got finished"?!? But yet, that is exactly where the problem was and now it kinda all makes sense that I was getting the testing results that I was seeing. I can't tell you what a relief it is to be back up and running and ready to go drive around some more! I WILL NEVER TAKE GROUNDING FOR GRANTED AGAIN!! So this begs the next question: do you guys know where and how the ground path was established originally? I'm thinking that the way my truck is set up could have been a "field expedient" repair that someone made somewhere along the line and it just never was put back the way it was supposed to be. I have the existing ground strap from the negative terminal on the battery which is still attached to the (now cleaned up) bolt on the battery tray. I think this part probably isn't correct. I also have a short ground cable that runs from the back of the block to the cab which seems like it was supposed to be there from the beginning. I have not been able to locate a connection from either the body or engine to the frame. Shouldn't that be connected as well? Any further advice would be GREATLY appreciated!!

 

Glad it's running

All I know is early 70's pickup trucks, which might apply to late 60's as well.

There was usually a ground from the battery to the engine block, and another ground from the back of the intake to the cab. Thinking about it, there should have been a ground from the battery (or cab) to the frame, but I don't remember seeing one in my '74 highboy that was stock. I seem to recall adding one "just to be sure". There might have also been one from the battery to the inner fender well as that was where the regulator was.

How many do you currently have?

 

Do not be so hard on yourself. I have seen a bad ground on a new truck cause mechanics to replace alternators and starters repeatedly.
The big battery cables go to the starter and engine. Needed for cranking.
Chassis grounds go from the battery or engine to the chassis generally speaking. Probably a 10 gauge or larger. Do not recall frame grounds on this size truck.
Sorry I am not much help on how they came.

 

Thanks, guys! That sounds perfect! I'm gonna get a new ground cable and run it from the negative terminal on the battery to a suitable bolt or stud on the engine block or the head. Then I'm going to replace that cable that runs from the back of the engine to the firewall of the cab. Lastly, I'm going to find a good place to ground both the engine and the cab (and probably the bed as well) to the frame. Hopefully that will keep me running for years to come!

 

The great news in all of this is HOW MUCH I have learned and how much better I understand my vehicle and what it needs to keep running! Thanks again for all of your help!

 

Now about what you owe and talking about beer on the forum. Shipping a beer to each of the Ford Heavy Truck Forum members should be sufficient unless you would just rather post a picture of your truck.
Hope you enjoy your truck for many years to come.

 

Ha! That's great, Tenwheeler! Man I would love to buy all the folks on here a beer (as I believe that by keeping our trucks running we have all EARNED one)! However, since the logistics of that exercise may prove even more daunting than the complexities of our electrical systems, I will have to resort to trying to figure out how to get a picture to show up here! Cheers!!