Electrical gremlin in the 67 Stout

MDH33

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I keep blowing the fuse for the guages in my '67 Stout. This truck has the same fuse panel as an early FJ40.

i-Gz8HLzh-L.jpg


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All of the wiring seems stock and in decent shape except that the original generator and voltage regulator has been replaced with a GM one wire alternator. The charge light in dash looks to be disconnected. Ground wires for original VR are connected to fuse block mounting screws. (White/black wires in pic above).

Can anyone help me troubleshoot this? I hate vehicle wiring... even in an old simple truck like this! 😋
 

MDH33

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Also, I do have an alternator for a 5r and and am hoping to swap it in with a compatible VR, especially if it might fix the fuse issue and get the charge light reconnected.

i-SJ3RCh2-L.jpg
 

subzali

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Find out what’s all on that circuit. You can disconnect each component (blower motor for example) and if it doesn’t blow then something along that line may be the culprit. That’s one idea.

Maybe start with, what’s all on the circuit that keeps blowing?
 

MDH33

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Its a 5A fuse. I think it's connected to:

charge lamp,
oil pressure,
fuel lvl,
temperature,
turn indicators in the dash,
guage lights when headlights are on,
reverse light,
Hazards,
 
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Rzeppa

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Look for a wire that goes through a bulkhead hole or other sheet metal that maybe used to have a rubber grommet that has disintegrated and the wire has rubbed against the metal edge of the hole in the bulkhead until the insulation has worn through.
 

SteveH

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On the face of it, a 5 amp fuse cannot handle hazards and anything else.

Each taillight filament would draw ~2 amps and more on inrush. So, this 5 amp fuse is running all the other accessories AND the blinkers? If you put it in reverse with the hazards flashing, you'd blow it for sure.

You may have explained this, but does the OEM diagram truly show a 5 amp fuse powering all those things (gauges, backlights, hazards, etc.)? I'd be tempted to install a 10 amp fuse at this point.

If the fuse blows the minute you turn the key, then I think Jeff's shorting point is correct.
 

MDH33

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On the face of it, a 5 amp fuse cannot handle hazards and anything else.

Each taillight filament would draw ~2 amps and more on inrush. So, this 5 amp fuse is running all the other accessories AND the blinkers? If you put it in reverse with the hazards flashing, you'd blow it for sure.

You may have explained this, but does the OEM diagram truly show a 5 amp fuse powering all those things (gauges, backlights, hazards, etc.)? I'd be tempted to install a 10 amp fuse at this point.

If the fuse blows the minute you turn the key, then I think Jeff's shorting point is correct.
The 5amp fuse is only powering the indicators for all of these things in the dash cluster itself. The actual lights are on another circuit. It does not blow right away. In fact when I replace the fuse it usually lasts ~20 minutes. I did try putting a 10amp fuse in when I ran out of 5's and it also popped after ~20 minutes
 
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DaveInDenver

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The 5amp fuse is only powering the indicators for all of these things in the dash cluster itself. The actual lights are on another circuit. It does not blow right away. In fact when I replace the fuse it usually lasts ~20 minutes. I did try putting a 10amp fuse in when I ran out of 5's and it also popped after ~20 minutes
Interesting.

Gotta say first, I know you know better than to do that. Putting a 10A in place of a 5A in old junk is how you melt down your cool Stout. ;-)

But since you've done it and lived to tell the tale it indicates a few things.

If you can post the exact numbers on the fuses it could be determined exactly but you can pretty roughly assume an AGC fast blow will hold 1x rating (e.g. a 5A at 5 amps) for at least 4 hours, 1.35x rating for 3600 seconds and 2x rating for 120 seconds. Beyond that the time to open decreases exponentially, so at 3x it's only hundreds to tens of milliseconds to blow.

So unless you're really far off on fuse-to-load you can usually get past initial inrush. A filament bulb can experience as much as 5 to 10 times nominal inrush, so a 2A bulb might draw 15 amps when it's first turned on but settles to 2 amps quick enough that it won't blow a 2A fuse since it's also following a warming-cooling curve. It gets trickier with non-resistive loads. That would be inductive things like motors and coils. Or when you stagger loads. So the first couple of loads don't do it but a 3rd or 4th inrush after a few minutes of heating up the fuse that does it.

Since both the 5A and 10A last 20 minutes then you can probably assume it's something large that's coming on at that point. If it was just constant load then if the 5A blows at 20 minutes the 10A will likely last indefinitely since the load is probably just a bit more than 5 amps.

But if a similar use allows both to last 20 minutes then the load has to be sufficient to blow both fast. What I mean is if it opens the 10 amp at 20 minutes then the load would be only *very slight* higher than 10 amps. But that sort of constant load would still open the 5A in just a couple of minutes.

Since both values last 20 minutes the load from zero must be about 5 amps and jumps to I'd guess 20 amps or more for some reason.

Are you sure you can't correlate it to maybe hitting a blinker. It could be as weird as your normal routine is to let the truck warm up for 15 minutes before leaving and it takes 5 minutes before you first run into a stop sign and hit your brakes, thus the first time brake lights come on or something like that.

And don't discount Jeff's idea but think dynamically, too. For example a short might only occur when you jostle the wiring driving over railroad tracks or when you turn left or right pulling only when the cab or frame experiences movement. If it's in the steering column it could be twisting a harness.

So the 20 minutes in your perspective might not actually be 20 minutes of electrical load. The fault is I think very short duration and thus easier to mimic in the garage.
 
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MDH33

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Sounds like I need to start going through it one item at a time, inspecting wires and disconnecting and seeing if it blows.

One problem is I haven't figured out how to get the plastic shroud off the instrument cluster to expose everything. It's probably super brittle and I don't want to break it.
 

HDavis

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Sounds like I need to start going through it one item at a time, inspecting wires and disconnecting and seeing if it blows.

One problem is I haven't figured out how to get the plastic shroud off the instrument cluster to expose everything. It's probably super brittle and I don't want to break it.
I can probably help you out with removing the shroud and cluster. Ive done it on mine several times.
 

MDH33

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I can probably help you out with removing the shroud and cluster. Ive done it on mine several times.
Seems like there's just the single thumb screw underneath, but it's attached along the top of the dash somehow.
 

DaveInDenver

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Can you verify the 3 tabs on the regulator? I'd guess one is ignition. The other two I'm not sure but I'm hoping are stamped F and E? Standard old type stock on the Stout or a Cruiser, etc. from the period?

Same question about the controller plug terminals on the alternator. It's from a 5R you said so I'm hoping it's the 3-wire Nippondenso alternator labeled F, N, E?

There'd be a big one for battery B. Not 100% sure why you'd have two big lugs unless the second is marked G/N/E meaning you'd use it for a heavy return/ground/earth path instead of the case via the mount.

The theory goes when you turn on the key to IG the F and E would regulate the field between F and E based on battery voltage. So you wouldn't need both N and E in that case on the alternator and should be able to ignore the green neutral.

This is basically what you're after.

wiring.jpg


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The 6-wire regulators would have used all 3 connections to the alternator, like this for reference.

Untitled1.jpg
 
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HDavis

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Seems like there's just the single thumb screw underneath, but it's attached along the top of the dash somehow.
Thats right. unscrew that screw and rotate the bezel towards the windscreen.
 

MDH33

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Can you verify the 3 tabs on the regulator? I'd guess one is ignition. The other two I'm not sure but I'm hoping are stamped F and E? Standard old type stock on the Stout or a Cruiser, etc. from the period?

Same question about the controller plug terminals on the alternator. It's from a 5R you said so I'm hoping it's the 3-wire Nippondenso alternator labeled F, N, E?

There'd be a big one for battery B. Not 100% sure why you'd have two big lugs unless the second is marked G/N/E meaning you'd use it for a heavy return/ground/earth path instead of the case via the mount.

The theory goes when you turn on the key to IG the F and E would regulate the field between F and E based on battery voltage. So you wouldn't need both N and E in that case on the alternator and should be able to ignore the green neutral.

This is basically what you're after.

View attachment 113548

View attachment 113550

The 6-wire regulators would have used all 3 connections to the alternator, like this for reference.

View attachment 113551
You're correct, IG, F and E on regulator.
E, F, N and B on alternator.

I have the large white wire from battery, a white/black ground, and a white/red coming from harness, It may be charge lamp? So I don't see any IG wire that would go to VR?
 

DaveInDenver

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I have the large white wire from battery, a white/black ground, and a white/red coming from harness, It may be charge lamp?
I'd guess the W/B and W/R are the F and E wires. Do you have the wiring diagrams? It shouldn't be that hard, the truck probably only has like 8 wires you'd need to trace. I'd be considering running new wires and new connectors in any case.

So you have an ammeter, too, or just a charge lamp? Regulators will have an L for that. You're sure the truck had a 3 wire mechanical regulator originally? Fairly certain that alternator will work with either type.

Untitled3.jpg

So I don't see any IG wire that would go to VR?
It's just an switched ignition hot. The first diagram shows it on a 15A branch so it may be relatively heavy.

In any case I think some wires may be missing. If memory serves the PO had changed the charging system, right? If he had gone to a one-wire GM (self excited and internal regulator) it's possible a lot of things have been removed.
 
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MDH33

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It had a generator originally. I can post the diagram but it's not color coded unfortunately.

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I got a Stout owner from the Facebook group to take a pic of the stock regulator, wire colors not very clear though.

i-t2BH2zv-X2.jpg
 

MDH33

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I might have found the culprit today. Took the instrument cluster out, everything looked good. The shroud didn't explode into a thousand brittle bits of old plastic as feared. All the wiring looked good except for the hazard plug which I disconnected. Drove it some and it blew another 5A fuse. Thought about when it blew and it seemed like when I put it in reverse. There's a switch on the transmission. Looked at the wiring and I think Jeff was on target as I found som abrasion on those reverse wires from the parking drum brake.. disconnected and it hasn't blown yet but still trying to figure out the overheat!
 
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