1968 Dart gauge help

-
J

John Stapleton

Well-Known Member
Joined
Sep 17, 2018
Messages
61
Reaction score
28
Location
California
So I bought my 17 year old daughter a dart rat rod to drive to school but the gas and temp gauges do not work. I pulled the cluster to clean and ground the voltage limiter and while I had it out decided to replace the headlight switch because the dash lights are not working either.I got the switch changed out and the cluster grounded and cleaned up but after installing it I went to hook up the battery...pos terminal on.. neg terminal on and BAM the fusible link smokes! Now I am pretty good with cars EXCEPT with electrical! I do know that the amp gauges are not good in these cars so can I test the gauge now that I removed the cluster again? PS- the wiring on this car looks to be all original and for the most part never butchered and the bulkhead looks good as well.Here are a few pics of the cluster after cleaning up and being grounded (got these tips from other post on here prior). Thanks in advance to all that can help... John

thumbnail_IMG_1706.jpg


thumbnail_IMG_1707.jpg
 
Since "you diddled" with it, likely something you did. Maybe you shorted the ammeter connections to ground. The ammeter is NOT grounded, so check each stud of the ammeter to the cluster ground. Should be open.

Wander over to MyMopar and download a FREE factory service manual, and there are also aftermarket wiring diagrams over there, which are sometimes easier to follow than factory, but sometimes not exactly complete

MyMopar - Mopar Forums & Information - MyMopar Tools/Reference

Also there's an article on 'curing' the bulhead connector problems, and even if you are not intending to do so, there is a simplified diagram there of primary power distribution

This is simplified, but shows the major main power. Notice that NOTHING is fused in this diagram, IT IS ONLY (somewhat poorly) protected by the fuse link

From the battery, through the fuse link, through the firewall / bulkhead connector on the BIG RED ammeter wire, and to the ammeter. On the other side of the ammeter the BIG BLACK comes off and goes to the WELDED SPLICE which is under the dash in that harness. That splice splits power off, feeds back out the firewall to the alternator, feeds power off to the fuse box "hot" buss, and feeds power off to the ignition switch. And it feeds power to the B1 terminal of the headlight switch. NONE of that is fused.

Catalog

amp-ga18.jpg
 
WHAT YOU CAN DO in order to find a short, while not smoking anything in the harness:

Get yourself a big wattage 12V lamp, such as a stop tail lamp (1157) or an old headlamp which has at least one good filament

I use an old stop/ tail light socket because you can wire it different ways for different jobs.

Hook this large wattage lamp in series with the battery ground. Go around and be certain everything is "off" including truck lamp, dome lamp, glove box lamp, everything. The lamp should not light. If it lights dim, it shows some sort of drain. If it lights up bright your short is still likely active.

Remove/ disconnect items until it goes away. There is a VERY remote chance something is wrong with the headlamp switch, so try it as well. Don't forget the alternator "big stud"
 
AMMETER: Did you have that apart? Or maybe the studs are just loose and one of the insulating washers broke / is missing.
 
67Dart273/Del will steer you in the right direction. I had the same issue with fusible link melting. We hadn't even had the car running since buying it. Finished putting car back together and I had an "extra" alternator that we used as the car didn't come with one. Well....smoked the **** outta fusible link, pulled the negative cable off lickity split. Spoke with 67Dart273/Del on the phone and he troubleshot it in 5 minutes. It was bad alternator.
Be sure to check that as well as above advice.
 
What the guys said.
Fusible link going poof means the battery positive got grounded.
Now you got to find out where.
First thing is visually check the wires and connections. The evidence may be visible!
Fusible Links in Charging Systems with Ammeter
 
Last edited:
John Stapleton said:
So I bought my 17 year old daughter a dart rat rod to drive to school but the gas and temp gauges do not work. I pulled the cluster to clean and ground the voltage limiter and while I had it out decided to replace the headlight switch because the dash lights are not working either.I got the switch changed out and the cluster grounded and cleaned up but after installing it I went to hook up the battery...pos terminal on.. neg terminal on and BAM the fusible link smokes! Now I am pretty good with cars EXCEPT with electrical! I do know that the amp gauges are not good in these cars so can I test the gauge now that I removed the cluster again? PS- the wiring on this car looks to be all original and for the most part never butchered and the bulkhead looks good as well.Here are a few pics of the cluster after cleaning up and being grounded (got these tips from other post on here prior). Thanks in advance to all that can help... John

View attachment 1715452389

View attachment 1715452390
Click to expand...
 
Thanks for all the answers you guys! I did wonder about your about answer#5 67Dart273.
I did try to loosen the 3/8 top nut holding the red wire and it wanted to spin and was somewhat loose/wobbly.I had to use 2 wrenches to back off the top nut. Could that be the issue? A possible broken internal stud! Also, where are the insulating washers supposed to be?
 
John Stapleton said:
Thanks for all the answers you guys! I did wonder about your about answer#5 67Dart273.
I did try to loosen the 3/8 top nut holding the red wire and it wanted to spin and was somewhat loose/wobbly.I had to use 2 wrenches to back off the top nut. Could that be the issue? A possible broken internal stud! Also, where are the insulating washers supposed to be?
Click to expand...
The two ammeter studs must be isolated from the cluster housing, so there must be one on the inside and one on the outside. Normally, those have one washer with a ?? step that centers in the hole. As I said (I think) earlier, with wires disconnected from the ammeter, check for continuity from the studs to cluster ground. They should be open to ground. The ammeter is in series with the hot feed

"If you must" you can bypass it for testing or whatever. Just get a small machine screw, bolt the black and red ammeter wires together, and tape them up.
 
John Stapleton said:
Thanks for all the answers you guys! I did wonder about your about answer#5 67Dart273.
I did try to loosen the 3/8 top nut holding the red wire and it wanted to spin and was somewhat loose/wobbly.I had to use 2 wrenches to back off the top nut. Could that be the issue? A possible broken internal stud! Also, where are the insulating washers supposed to be?
Click to expand...

You wont find isolating washers on every assembly. Some have the amp gauge poked through metal housing alone. Isolator/fiber washers would be req'd there. Most have amp gauge trough circuit board that has all copper removed in that area so the board material serves as isolator. The gauge itself should have small shoulders cast around the studs which locates them away from metal housing there.
Regardless of all that, If any gauge has loose wobbling/turning studs, the gauge is broken. Use a 10-24 nut and bolt to put the 2 ring terminals together off the gauge. Tape it up good.
 
Well I tested the gauge with a meter this afternoon and no continuity so I pulled it out and pretty much think I found the problem. Kind of a wimpy piece of cardboard for an insulator protecting it from the housing. I think when I reinstall another gauge I will use maybe 5 or 6 layers of tape or a piece of plastic to insulate next time. Thanks for all the help 67dart273 and everyone else for the shout outs..
Do to my rudeness when originally posting I will now include a few pics of the daughters ride to school for the next year or so. 360/904 with mild comp cam(440 lift), edelbrock performer, and holley 600 Street Warrior carb. Mopar or no car...

thumbnail_IMG_1709.jpg


thumbnail_IMG_1710.jpg
 
John Stapleton said:
Well I tested the gauge with a meter this afternoon and no continuity so I pulled it out and pretty much think I found the problem. Kind of a wimpy piece of cardboard for an insulator protecting it from the housing. I think when I reinstall another gauge I will use maybe 5 or 6 layers of tape or a piece of plastic to insulate next time. Thanks for all the help 67dart273 and everyone else for the shout outs..
Do to my rudeness when originally posting I will now include a few pics of the daughters ride to school for the next year or so. 360/904 with mild comp cam(440 lift), edelbrock performer, and holley 600 Street Warrior carb. Mopar or no car...

View attachment 1715452663

View attachment 1715452664
Click to expand...
The cardboard certainly looks like where it (the battery) grounded.

Insulating washers and materials are often some dsort of fiberboard. That's usually pretty good as it doesn't distort with heat - as plastics can.
To be sure we're on the same page.
The studs connecting to the shunt plate sould be snug - no looseness at all. And no breaks in the plate.
Continuity between the two studs should be perfect. On most meters it should show resistance as infinity or very very small.
If so, then you're good to go.
Just keep it insulated from any ground.
 
'68
Fusible link terminated in the bulkhead connector. Yes?
Easiest will be if you can buy fusible link already made up.
That should have the correct terminals so they mate and lock in well.

Pictured below is original '67.
'68 should be the same other than the position in the bulkhead connector.
upload_2020-1-14_18-30-48.png
 
After reading your reply Mattax I went out to retest the gauge and came up with this. Is this gauge still usable as I do not think I was testing it right before? I had to add the larger bolts because the the studs are kind of loose when I tried to test it again. Should the studs be wobbly or tight in their fittings without the retaining bolts that obviously will firm them up after installation. Also the fusible link I believe is from a later year car because the harness connector is different. I think it was changed out prior to me owning the car. I think that shouldn't be to much for concern as I think the links are the same except for the harness ends. Thanks for your time Mattax!

thumbnail_IMG_1714.jpg


thumbnail_IMG_6279.jpg
 
John Stapleton said:
Should the studs be wobbly or tight in their fittings without the retaining bolts that obviously will firm them up after installation.
Click to expand...
The studs should be tight in the plate. They are press fit and should not wobble in their holes. Either fix it or replace it. I would not use it without those being secure.
That's the connection to the battery. As shown in the diagram 67Dart273 posted above, it carries all the current to charge the battery. Right after starting, that can be 20 to 30 amps although should quickly go toward zero as the battery charges up. But if the battery was run down, its going to run pull more current over a longer period of time. That's when that poor loose stud is going to cause heat and more looseness. Its downhill from there.

I will say this. Usuing a digital multimeter, two good ammeters I checked showed .1 Ohm, same as you pictured. That may be as good as it gets with a basic meter.
See here Ammeter measurements (in charging system road rage)

John Stapleton said:
Also the fusible link I believe is from a later year car because the harness connector is different. I think it was changed out prior to me owning the car. I think that shouldn't be to much for concern as I think the links are the same except for the harness ends.
Click to expand...
Yes I've seen that connector on later cars. The important thing is that the connections are good. The male terminal that goes in the bulkhead connector needs to be the correct length and not back out. That seems to be the same pretty all years that had this arrangement.
 
Last edited:
Time for a new gauge and fusible link! Thanks Mattax, 67Dart273 and everyone else!
I am now much more educated on this issue and hopefully I can pass it on to the next person!

Cheers!
 
John Stapleton said:
Time for a new gauge and fusible link! Thanks Mattax, 67Dart273 and everyone else!
I am now much more educated on this issue and hopefully I can pass it on to the next person!

Cheers!
Click to expand...
'fraid so.
Now I see in the second photo what you did.
You tightend the studs by running down two nuts over them.
That would work if there is room for the nuts when reinstall;
then use the original nuts for holding the wires to them.

I edited my post to add the link where I tried to measure shunt resistance.
.1 ohms was the resistance of the meter leads. So the shunt is essentially zero resistance when measured with a typical digital multimeter.

People have repaired or reinforced the press in studs. 67Dart273 has posted examples of those. Basically it involved soldering. The trick is not messing up the movement which means taking the gage apart.
 
Last edited:
If you're in time crunch, connect the two ring terminals together and bypass the ammeter.

If the car has a working cigarette lighter, there are voltmeters that can be stuck in there.
@toolmanmike

A voltmeter will not show quite the same thing but is still plenty useful.
If it shows 13.5 to 14.5 Volts with the engine running, that's normal and you can generally assume the battery is getting charged.
If it shows 12.5 Volts or less, you know the alternator is not producing power and the battery is probably discharging.

One more thing while I'm thinking of it.
Before the final hook up the battery to the repaired system, put a test lamp in line.
If it lights up, there's still a short from battery positive to ground.
That way you will know without burning out another fusible link.
 
Last edited:
toolmanmike said:
I have these in each one of my cars. They work great. Voltage displayed when plugged in and amps displayed when you plug your phone in to charge.

3.1A USB Dual Ports Car Cigarette Lighter Charger 12V/24V Digital LED Voltmeter | eBay
Click to expand...
Thanks Mike.
That must just be amps to through the USB connecter to the phone.

I think there may be enough room to give the gage its own mounting nuts. Maybe with a drop of locktight.
But figured he might want some options.
And besides its nice to be able to get voltage reading even when the ammeter is working.
 
There are different meters that display amps and volts at the same time. They have a inductive pick up coil for the amps. I used one for a pid controller I built. E bay has many different ones. All around $5.
 
You must log in or register to reply here.
-

Back
Top