So we thought that we were smart to trace and clip the wires to the ammeter, to prevent the Cougar voltage meter from receiving any unwanted electrons:





But after supplying power to the volt meter we learned that voltage passes through the gauge to the ground side and may be(?) affecting the other dash functions (e.g. turn signal switches, etc.).



So, I assume we need to electrically isolate the gauge (nuts) from the printed circuit board. Who has done this before and what worked, please?

 

That's really strange. And pretty much how I would have connected it.

As you found, the ammeter isn't connected to any other part of the cluster. At least it shouldn't be. It's really a zero center millivolt meter reading a voltage developed across a shunt resistance. In this case, the wire between the alternator output and the battery terminal on the solenoid.

Clipping those wires at the plug should have no effect on the gauges nor any other part of the electrics. However, the plug doesn't look the cleanest and the printed circuit looks a bit tarnished also. Try cleaning them with a cotton swab and alcohol or a pencil eraser or contact cleaner if you've got it. Super light passes with 600 grit paper would work but the printed circuit is thin and won't take much abuse.

The other thing I think I see is that there might be corrosion or water damage on the conductor side of the printed circuit. If that's true, it might carry enough current to cause trouble with the other gauges. A careful scrubbing of the other side might fix it, just make sure it's dry before you apply power so it doesn't track again.

Er, rereading that, I'm not so sure the copper is exposed except at the connections but it's worth a look.

Michael

 

Thanks Michael. I ordered a new circuit board but the wrong model (idiot light version) came in. I have been too busy trying to button up this week's project (another thread) to see if it was me or LMC to blame. I will use my ohmmeter to test continuity between the hot side of the voltage gauge and other places on the circuit board. So far I know that voltage passes through the gauge to the ground side of the circuit board.

 

All, fuel gauge isn't working. The turn signals:
- left works fine
- right does work

The emergency flasher results in a low voltage look (i.e. bulb barely lights) on the left and nothing on the right.

At this point, I'm ordering three new gauges and a new circuit board to eliminate anything old causing an issue. Will still appreciate any advice re: isolating the volt gauge (or not).
p.s. Jeff's Bronco Graveyard sells the gauges for $60 each; better than LMC at $85

 

Good day,

I did the same conversion two weeks ago. I did it slightly different that you did. I cut the amp wires about 3" from the gray connector that goes into the instrument cluster. I sealed the cut amp wires with heat shrink. I then tapped into a switched source voltage wire (I have a fused wire to my Ford 8 Track in dash unit so tapped there as it was close by and would not have to add another fuse). I then added a ground wire and ran it to the ground point that has a couple of other wires grounded using a small bolt on the instrument panel/steering column support. The source wire and the ground wire were soldered and shrink tubed to the wires coming off the gray connector that had been for the amp meter. I used the same current paths on the circuit board that were for the ammeter but now one was switched source and the other ground. Put it back together and started it up. Everything worked as designed. At full charge the gauge needle is almost at C and after a few minutes settles about halfway between the 3rd hash mark and C.

I am curious to know what you find. My circuit tracing looks like yours, where the two paths for the amp meter are isolated from anything else. Maybe the other connections between the printed circuit and gray connector are not 100% and resistance is causing some voltage drop.

 

lbcarguy, thank you for this information. MUCH better to terminate my sourced 12V and ground into the gray connector than running wires directly to the back of the gauge. I was worried about putting 12VDC into the circuit tracing, but if it worked for you I will rewire it that way when my new tracing sheet comes in from LMC and I have time to get back into this. I know I don't like driving around without a gauge set, but there are worse things... I appreciate you sharing your experience. IH -

 

Hi,

You are welcome. For my truck, the best part for me after the install was taking out the after market voltmeter I installed under the dash. The main reason I did the wiring through the connector was so it would make removal and install of the instrument cluster easier in the future.

I teach auto electrical level 1, 2 and 3, along with engine performance (comp engine controls) at a 2-year college auto tech program. I don't know everything but glad to help when I can.

Mike

 

That's a great idea. I appreciate sharing what I know or learning as I do it, or learning from others on this great resource. I will post again when the carpet and dash parts come in to close this thread / project.

 

I'm about to install my converted gauge, and I just plan to seal off the exposed ammeter contacts on the printed circuit and just fold it back out of the way. Seems like the easiest thing to do, as there is no cutting of existing wires.

 

Okay, you've piqued my curiosity... how do you plan to seal off the exposed contacts on the printed circuit? I put some thought into that option but don't really see a clean way without trimming the circuit material. I do note that the ground wire shouldn't need to be cut (i.e. that only one loom wire needs to be cut to make that option work), although mine is already with an independent ground awaiting the circuit.

 

Idaho......look the gray plug over closely......there should be a way to release the metal contacts inside the plug.......a small pick or even a smashed paper clip might work.....I don't have my dash apart right now so I cant go look and give you anything more precise....anywhoo.....If you can just remove the contact from the cavity and then shrink tube the metal portion of the contact once it is removed............no cut wires......no electrons flowing to the printed circuit........that's how I plan on doing mine when I get my volt meter.......just my 2 cents.....

 

I plan to use some liquid tape over the exposed contact and then cover it with tape as an added measure.

 

I used a couple nylon washers to isolate the studs, and then a couple small wingnuts for quick disconnect ability if I ever need to pull the cluster again.