ammeter blowing fuses/ getting hot

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CLAY72dart

CLAY72dart

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hello this is clay posey from out in South Carolina I am in the us navy and don't have much time on my hands but I was wondering if you could offer me some help or point me in the right direction. everything on the instrument panel disconnected it will still pop a fuse up to 30A when I hook up the positive and negative to the ammeter. positive is ran directly from starter relay to the ammeter with only a inline fuse in the way.
Ammeter in instrument cluster short-circuit
 
Simply "bolting the wires together" does not solve the problem. Part of the problem, actually MOST of the problem, is the terminals in the bulkhead connector
 
67Dart273 said:
Simply "bolting the wires together" does not solve the problem. Part of the problem, actually MOST of the problem, is the terminals in the bulkhead connector
Click to expand...
True, what you really want to get is crackedback’s alternator bypass wire. Juice still goes through the firewall, but less. His headlight relays are awesome too.
 
Lord Sparky said:
True, what you really want to get is crackedback’s alternator bypass wire. Juice still goes through the firewall, but less. His headlight relays are awesome too.
Click to expand...
Yeh. But even with that you need to repair or bypass the bulkhead terminals. They are still used, just not as "stressed"
 
My "goto default" argument against Mopar bulkhead connector terminals used to be electric furnaces. "In a previous life" I serviced HVAC/R and lots of heat pumps and or electric furnaces. They use those 1/4" spade/ flag terminals at the heating elements/ protectors/ relays in the controls. The typical 240V electric strip is nominally 20-25 amps so that is what is on those and THEY USED TO FAIL FAIRLY REGULARLY so if they are failing at only 20-25A you can imagine how under-designed they are at say, a 55A alternator

Here's an example of an old school electric strip unit from "back in the day ish"

controls2cs'.jpeg


controlscs.jpeg
 
67Dart273 said:
My "goto default" argument against Mopar bulkhead connector terminals used to be electric furnaces. "In a previous life" I serviced HVAC/R and lots of heat pumps and or electric furnaces. They use those 1/4" spade/ flag terminals at the heating elements/ protectors/ relays in the controls. The typical 240V electric strip is nominally 20-25 amps so that is what is on those and THEY USED TO FAIL FAIRLY REGULARLY so if they are failing at only 20-25A you can imagine how under-designed they are at say, a 55A alternator

Here's an example of an old school electric strip unit from "back in the day ish"

View attachment 1715970520

View attachment 1715970521
Click to expand...
That looks REAL similar to our "now-ish" strip unit.
 
CLAY72dart said:
hello this is clay posey from out in South Carolina I am in the us navy and don't have much time on my hands but I was wondering if you could offer me some help or point me in the right direction. everything on the instrument panel disconnected it will still pop a fuse up to 30A when I hook up the positive and negative to the ammeter. positive is ran directly from starter relay to the ammeter with only a inline fuse in the way.
Ammeter in instrument cluster short-circuit
Click to expand...

Looks like you found at least one short in your other thread begun on Saturday.

Here's what's going on:
The ammeter is a part of the battery power feed. There are two different wire colors used to insure the ammeter reads the correct direction.
When the wires are connected, black is hot, just like the red is hot.
As you discovered, the black wire is connected to the MAIN JUNCTION. This is a WELDED SPLICE.
Everything connected to the welded splice is hot.
The main junction joins the two power supplies (batery and alternator) to the the main feeds as shown in the drawing below.
Not everything is fed through the fusebox.
With the key off, there should still be power at the fuses for the dome light, brake lights, tailights. There should also be power for the headlights (no fuse - circuit breaker inside the headlight switch).
The fusible link is a last ditch protection measure against battery shorting to ground.
upload_2022-1-1_13-31-34-png.png


One more big clue and caution.
The ammeter shows current flowing in or out of the battery. In other words battery charging and discharging.
Its another useful tool.
Its calibrated roughly 40 amps to 40 amps.
Anything close to 40 amps either way is DANGER DANGER
 
67Dart273 said:
Simply "bolting the wires together" does not solve the problem. Part of the problem, actually MOST of the problem, is the terminals in the bulkhead connector
Click to expand...

Del, your are correct sir. I also added a parallel path wire (12 gauge wire (with a fuse link)) to lessen the load through the bulkhead connector.
 
your ammeter is bolted into the dash pod/ frame by the 2 bolts that are the main electrical connections to the meter
these bolts/connections are threded rod with a sandwich of insulation, 2 or 3 nuts and some washers

the ammeter connectors and the nuts used need to be totally insulated from the dash pod/frame
this is done with fibre washers either side of the dash pod between it and the nuts that are used to possition the gauge and hold it in place
1 side has a plastic washer that is like a top hat that sleeves the stud... the top hat section slips down the hole in the pod to stop the threaded section shorting to the inner diameter of the hole

if the ammeter has ever been over heated this insulation fails and causes a direct short of battery to body

to fix
take out dash pod
remove ammeter gauge from it

replace all insulation with new fibre washers and lengths of thin plastic tube made from something that is high melting point. electronics stores have just the thing for insulating the tabs on power transistors etc find somthing that sleeves the studs and provides a washer section to keep the nuts form hitting the pod

bolt it back into the pod and check with your multimeter set to continuity that there is no beep or that there is infinite resistance between the case and each stud

this seems to fix many "broken" ammeters. they aint broken its just the insulation went hard and crumbled or melted..

with an properly insulated gauge if the fuse stil pops your issue is a short in another cable
potentially the main feed pin in the bulkhead connector has shorted to a neighbour.
drill right through and push a fat insulated wire through and basically bypass the bullet connector that is causing the problem by connecting the orginal wires to either end (suggest solder and shrink sleeving would do the job) its a bodge but it works

Dave
 
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