Grounding the instrument voltage regulator

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70DartMike

70DartMike

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Are you not supposed to ground the instrument voltage limiter? I did a bunch of reading here before doing so, but I may have fried it.

My problem is the fuel gauge doesn't work. While re doing the car (1970 Dart, standard cluster) I installed a new sending unit, new line, new ground strap at tank, and new voltage regulator. The gauge still didn't work. I grounded the sending wire at the tank and got someone to watch the gauge with the key on, it didn't work. So I pulled the cluster out and replaced the fuel gauge with another I had. I then grounded the voltage regulator, because I had read here it needs to be properly grounded. I turned the key on, and the gauge went to a 1/4 tank, then I saw/smelled smoke from something melting. I immediately shut the key off.

My question is, did I fry the voltage regulator? I didn't kill any fuses. Or did I most likely kill the gas gauge?

Any input is appreciated.
 
It's hard to guess without being there and seeing for myself, but I would guess that whatever burned it out in the first place was still present. The instrument panel voltage limiter needs a ground to work in the first place. So if that's what you grounded, then that should not be the cause of further shorts.

Search this site for further info on testing the voltage limiter, and then test it out.
 
Everything on these cars needs a chassis ground path. This includes the instrument panel which includes the instrument voltage limiter. You may have noticed the limiter has a chassis ground leg off the back of it. Nothing about the instrument panel will function properly while it dangles from its harness connectors. The chassis ground path isn't completed unless the panel is screwed to the dash.
Adding a dedicated ground wire can only improve panel performance but.. If you want to power up the panel and test it before screwing it to the dash thus completing its chassis ground path, adding a ground jumper wire is absolutely required even if its only temporary / done with alligator clips.
I cant guess what part you let the smoke out of.
I can say some have let smoke out of a speedometer cable. That part was never supposed to have smoke in it.
 
And by the way... temp and oil gauges use the same limiter. You haven't said if those work or not.
 
On my 67 there was a BUNCH of stuff wrong with the cluster. That is why I keep preaching to check these END TO END as a SYSTEM. Visualize in your mind the entire path, from sender, through each harness connection, plug, connector, wire, pin, mating female connection, the PC board, etc.

On the cluster itself there is a number of factors, including loose broken harness connector pins, poor connections at the regulator, poor connections at the gauge studs, of course, bad regulator and or gauge units, and poor ground from the cluster / PC board(s) to the body of the vehicle.

On my 67, where the regulator plugs into the PC board, there are brass finger contacts which form the "socket" into which the regulator fits. None of these brass fingers were reliably making connection to the PC board. I had to solder jumpers from the brass fingers to the board traces.

As Red said, add a ground pigtail from the cluster. Bolt this to a solid ground, such as the column support brace.
 
RedFish said:
And by the way... temp and oil gauges use the same limiter. You haven't said if those work or not.
Click to expand...

No, they don't work.

Where is a good spot on the cluster to attach a ground lead? The cluster doesn't appear to have a ground coming off it, I just assumed it was in the harness that plugs into it.

What are the chances the gas gauge was fried? Are they usually last to go?
 
As Fishy stated Mike the panel is chassis grounded meaning the screws carry the ground to the dash frame , if you look at the circuit boards the guages are mounted to you will see copper around all the mounting point screws and holes tuck a wire under one or two of these screws and connect it/ them to the dash frame to create the complete ground path , the pot metal of the cluster acts as part of the ground circuit that's why there is no obvious ground lead . Hard to say whether you fried the gauge or the regulator you will probably have to try a known to work regulator from one of your other cars in place of this one to test that .
 
70DartMike said:
No, they don't work.

Where is a good spot on the cluster to attach a ground lead? The cluster doesn't appear to have a ground coming off it, I just assumed it was in the harness that plugs into it.

What are the chances the gas gauge was fried? Are they usually last to go?
Click to expand...
Somewhere around 74 the gauge housing changed to plastic in which case a ground harness to the various items would be present.
If you had a rally panel I could say the Phillips head screw at bottom of center pod is the best place for a added ground wire.
Most of the small screws that attach the circuit boards to your pot metal housing are very short, weak, self threading attachments.
Without having your panel to look at, I'm going to recommend the Phillips head screw that hold the noise suppression cap in place.
When I add a ground wire I use a ring terminal and a toothed washer. 3 inches wire away I place a male female spade connection for service disconnect. I take the final connection somewhere like near the fuse box so if I do need to pull the panel outward for testing it, I don't have to remove my ground connection in that process.
 
"No, none of them work" Here's a thought... The wire terminal at oil senders rarely have a insulator on them. If that bare terminal falls off and shorts to ground, IT WILL FRY the oil gauge, limiter, or both. An oil warning lamp doesn't apply.
Temp sender wires normally have their insulator on the terminal but that wire is sometimes pinched under a valve cover or otherwise shorted,
again frying that gauge, the limiter, or both.
 
Thanks for the input. I'll try the ground lead from the cluster.
Also, none of my cluster lights work (other than turn signals and high beam indicator). This could all be cause of a bad ground.

A few of my prongs have recently come a bit loose.. Is there a simple fix for these? Or should I find a cluster that still has tight ones?
 
all of the bulbs require chassis ground except the park brake indicator. If illumination bulbs don't work the problem could be a blown fuse, bad headlight switch, other.
 
Alright, sounds good.

Which prong does what on the voltage regulator?

And what's an easy way to test to see if the one I thought I melted, is actually alright? Any kind of bench test?
 
Its fairly easy to tell what slot is what when looking at the circuit board.
If you're looking at only the limiter, ground comes off the top or back of the can.
12 volts is horizontal spade in the center. Pulse voltage out is vertical spade at opposite end from ground.
Testing the mechanical limiter and proving it is good is nearly impossible. It puts out a pulse voltage that makes most digital volt meters act crazy. A good analog meter will display better.
 
Well, I figured out what was smoking. One of the copper strips on the printed circuit board melted. So, I pulled a gauge cluster from one of my parts cars, and the gauges and circuit board look perfect. I don't think It's ever been out of the car. I also managed to find a couple voltage regulators at the parts store, so tomorrow I'll finish putting everything back together and I'll let you know how it goes. I'm also running a ground lead from the cluster to the dash frame.
 
I just went through this, and couldn't get the cluster out of our 71 Dart. So I reached up behind, pulled the limiter out, and made a pig tail and mounted the limiter in the drivers side kick panel.Grounded it, and created a new ign. wire to it from the fuse panel.
I also found somewhere between the plug in wire harness and the dash cluster the wire for the fuel gauge was dead. I cut the fuel sender wire there and added a new wire up to the gauge. I used female plug ends and plugged all the new wires directly to the gauge on the mounting posts. It works perfect.It feed the temp gauge too.
I am sure there is an issue with the traces on the board or the pins.But to much drama to pull it out. Maybe later.But yes, most the times it's the pins, which can be fixed with the cluster out.
 
The copper trace on the board is the weakest link. The entire circuit may have been overheating until the burn through or there may have been a short right there on the board. A pin pushed though and grounding to the inst' housing would do it.
 
Well, the fuel gauge works now. However, when I turn the key, the starter makes a loud click and won't engage. Odd. It was starting fine before, what changed??
 
Don't know, maybe you lost some continuity through the battery terminals. Surely you have pulled and put a battery connection several times during all this.
 
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