poppin' fuses

W

WQ59B

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'40 COE, stock, 6-volt, haven't run it yet.
ALL new wiring, new battery. Took apart & cleaned/checked ignition switch. New NOS gauges. New fab'bed 'fuse block'. Good continuity on each new circuit.

Connect battery: tails, headlights (low & Hi), dash lights work. Hit ignition toggle switch & 1 of the 2 fuses blows.
Disconnected gauge lead from ignition switch, no blown fuse.
Reconnect gauge lead, fuses pops. No fuse pop on coil lead.

Getting continuity from gauge lead wire WHILE DISCONNECTED to the ignition switch toggle! Current theory is somehow either the oil or fuel gauge is bleeding power out thru the gauge cluster into the dash, looping thru the column & thru the ignition toggle. Suppose it could be looping around the long way and coming up the steering column, too.

Going to try to insulate the individual gauge terminals in case they are hitting the rear cover of each gauge.

Any of this make sense? Have gone thru maybe 10 fuses trying different theories. Very frustrating.
 
Not knowing what you used as a wiring diagram, kinda hard to guess, but one possibility comes to mind: The ammeter has only a loop through it, nothing hard wired to it.
 
Ford38V8 is right. Ford's stock amp gauges (assume your not using a modern gauge) only function using a loop behind the amp gauge. Perhaps the insulation on the wire loop behind the amp gauge is damaged and grounding-out onto the meter body when you turn on the ignition switch.

As you noted, the trouble's in your gauges or their circuitry. Try taking the wire loop off the back of the amp gauge and leaving just the oil and fuel gauges connected. If a fuse still blows reduce the number of gauges to one and test again - this should indicate which gauge circuit is grounding. If the oil and fuel gauges are faulty they would either not register anything, read to their max capacity, be internally shorted, or as you suggest, maybe the ignition switch or a gauge terminal is hitting ground.
 
Ampmeter isn´t switched so if that was the issue it should short out as soon as connected to battery.

Check for overtightened connections at meters if they have cut through the insulation.
 
Cross-referencing '40 & '41-42 Ford schematics. Both have degrees of generality to them; different arrangement of gauges, electrical bits I don't have, etc.
(Stock) ammeter wire is new, correctly 'passes thru' the ammeter loop fully insulated. That works fine, IE; when the headlights are switched on, it dips.

As I've not yet started the truck, can't see if the oil pressure gauge works. Tried to bench test the fuel sender, ohm meter was all over the place. Opened the unit and it's beautifully clean inside, nothing obvious, cleaned the 'contact' nub. That's an unknown too until I get gas in the tank. Fuse blew both with the sender secured to the tank and hanging by string from the cab roof (IE; not touching anything).

In taking the (NOS) fuel & oil gauges apart: they have insulating paper on the backs of them, and a fiberboard insulator on the inside, between the gauge's innards and the gauge backing. It looks like the gauge terminals come exceedingly close to the backing, but I find it hard to believe this is the issue. But since the oil & fuel are the only 2 electrified gauges (vs. temp & ammeter), something, I assume, is wrong here.

To restate; I'm getting continuity from the wire off the gauge lead jumper (connects the oil & fuel gauges to give them power) and the dash panel. IF that's the only problem...
 
Difficult problem.
I usually like to start removing one connection at at time. In this way, you can verify that each connection is not causing the problem. Remove, each connection until you get the problem to stop.
Just a thought, could that terminal board be bad, If it is new maybe you got a bad one, if it is old maybe there is a short. Personally, I would start there. Realistically there are not that
 
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A simple benchtest of the instruments is feed them 7v and ground them through a 50ohm resistor should give you about halfscale reading so you know they work.
The resistor needs to be big or it will smoke and fry !
While hooked up measure between housing of meter and ground with a voltmeter, if you get a reading there you got the problem.
 
Agree with FrankWest except the order of testing. I'd disconnect all but one connection, then add one at a time until the fuse blows. This will save fuses unless you're a lucky guesser.
 
Curt in AZ said:
Agree with FrankWest except the order of testing. I'd disconnect all but one connection, then add one at a time until the fuse blows. This will save fuses unless you're a lucky guesser.
Click to expand...

Sounds like a good plan, too. But with only one connection maybe nothin will work?

I recently put new harnesses in my 1933. Simpler wiring than yours but anyway. I started at the battery, making sure all the connection there were all goo and sound. Then started to add another connection, and slowly another making sure everything was fine sound and clean. You get the idea.
I was not sure you wanted to disconnect everything to start, but that is the better way to go as Curt said.
Without the generator running there is only one source of power..The battery.
So work out from there.




Do I only have to p
 
Those old King Seeley gauges work off of a current based system that uses a tiny heating coil to move a bimetallic strip to work the indicator needle and the sender mechanism. As flatheadmurre mentioned, a seperate test of each gauge and sender will let you know what works and what doesn't. Temp senders are available if they are bad but the fuel senders are not. There may still be some good NOS or used indicators/senders out there if one is bad but it might be a wire. It could be a short to ground in one of the indicator systems. It could be anywhere in the system too. Wires to fuel senders are long and vulnerable. Temperature systems are not as long but can still short out.
 
BB trucks have one fuse, that monitors the light circuit only. What are your two fuses monitoring? Why is the ignition system on a fuse?
 
Been working from the Van Pelt '41 wiring diagram:
http://www.vanpeltsales.com/FH_web/...cs/Flathead_Electrical_wiring1941-42truck.jpg

That shows what my truck had / has : (1) ignition resistor and (2) "circuit breakers" IE: fuses.
- - - - - -
Here is the OLD fuse block in my truck (since completely replaced):
DSC04497_zpsugqrwyfr.jpg


- - - - -
Here's a 'during' pic of the re-wiring, you can make out the new fuse block.
DSC04504_zpsdhgsptb6.jpg
 
Unless something is not like if appears in these photos, the ignition is not connected to the fuses shown.

Just looked at the wiring diagram you have linked to. Again, the diagram does not show a connection to the fuses, in fact it does not show any fuses! The diagram shows two circuit breakers neither of which is connected to the ignition circuit.

Not sure what your seeing that leads you to believe there is a fused connection to any of the following, ignition switch, ignition resistor or coil? The terminal on the fuse block is used for the major connection point for all of the hot wiring from the battery, is this the source of the confusion? Just because the main hot connection point is a terminal on the fuse block does not mean it is fused! In fact, this is typical of the way Ford wired the vehicles.

One of the circuit breakers connects to one side of the lighting switch and the second circuit breaker connects to two locations. One is the other side of the lighting switch and also to the brake switch. Again, this is typical of how these years of Fords where wired.

If turning on the ignition switch is blowing a fuse (your truck seems to have fuses in place of the CBs) then the most likely issues would be that it is miss-wired! I would start by tracing the wiring out and see where the issue is.
 
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Yea, I know, but it's not that tough- many are labeled and there's not many to begin with. Only time it's a hassle is when you're tracing thru the firewall grommet. Often it's 2 of us working on the wiring together. Hey, I had this spool of wire…… ;)
 
May be tougher than you thought! Something is miss-wired, there is no way I can think of that turning the ignition switch on would blow a fuse, there shouldn't be any connection that would result in a path to a fuse. Have you ever seen the colored tape? Might get several rolls of different colored tape and wrap the wires in several places along the length of a wire. Several colors should do, you can use combinations of two colors and also use a marker to place black strips on the tape. That should give you enough combinations.
 
Already traced & re-traced & re-traced. 2 sets of eyes, 2 partially-intact brain stems.
Will go over again, disconnect stuff, eliminate possibilities...

JSeery :: "Unless something is not like if appears in these photos, the ignition is not connected to the fuses shown. Just looked at the wiring diagram you have linked to. Again, the diagram does not show a connection to the fuses, in fact it does not show any fuses! The diagram shows two circuit breakers neither of which is connected to the ignition circuit."

The 'ON-OFF' switch is labeled 'ignition switch' on the schematic. That switch has a 'batt' terminal the schematic shows connected to the 'fuse block'. Where you lose me is the difference between circuit breaker & fuse; is the wiring routing OK but the fuses need to be replaced with circuit breakers?

My buddy is the lead man on the electrics, I get befuddled @ the conceptual level.
 
looking at pic of gauge cluster with two gauges....diagram shows 4 wires, i can only see 3??....maybe the gauges need to be installed in dash??.....6V positive ground system??..maybe you have a short in the ignition switch??.....Mike
 
There should be no fuse or circuit breaker in the ignition circuit, so there is no way than turning the ignition switch on would blow a fuse. If I understood you correctly you were saying that the fuse blows when you turn on the ignition switch. That can't happen if it is wired correctly so you have to be missing something. An easy test would be to get the hot wire to the ignition switch completely away from the fuse panel. That will eliminate that element of confusion. I can draw you up a diagram on how to wire it.
 
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