• 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
How not to add an ammeter
So, I knew that previous owner(s) added factory tach and gauges to my car. I never noticed the ammeter do much. (which isn't out of the ordinary for this vintage) I knew that wiring it wrong can burn your car down, so I had always planned on going through and checking out the wiring.

Yeah, they did it wrong, and looks like they were on their way to burning the car down.

So, the alternator harness, voltage reg harness, and the fusible links were always kinda in a bundle that was intertwined... So I started buy unwrapping this lump. What. The. F!ck.

[Image: IMG_0767_zpsabe7f496.jpg]

The small grey wire was taped at it's end, hanging amongst the cluster. Following it up the harness revealed it was broke, and burnt, and spliced.

[Image: IMG_0768_zpsaa215607.jpg]

[Image: IMG_0769_zps5b8d5ba2.jpg]

It followed along with the double heavy yellow wires that were bolted to the fusible link, up to the next lump in the harness.

[Image: IMG_0770_zpsa359c880.jpg]

Where a second grey wire was spliced in, and joined the first in a twin lead, up the harness, and through the firewall grommet.

[Image: IMG_0771_zps862b5534.jpg]

[Image: IMG_0772_zps7207fd0d.jpg]

And over to the cluster where it was "plugged into the center gauge harness... (with half the plug missing)

[Image: IMG_0773_zps776b30e8.jpg]

This made the harness unhappy.

[Image: IMG_0774_zpsfd804c66.jpg]

[Image: IMG_0775_zps6809930a.jpg]

So I set about removing their attempt at ammeter wiring. This was the large lump under the tape.

[Image: IMG_0776_zpsf8de18c7.jpg]

[Image: IMG_0777_zps231568de.jpg]

I was able to melt the solder out and was left with the original main wire.

[Image: IMG_0778_zpsb1cb0388.jpg]

Now.. to continue and unfuxor this harness. Rolleyes

1973 Mach 1 Q code 351 4V, 9A paint, standard interior, 3.50 rear, C6 trans.
"How NOT ta add an amp meter" Is more like it!

I had same issues with the engine harness wiring been jacked up too many times over the years and is just a
big electrical fire waiting to happen. I have witnessed several car-b-ques over the years because of such wiring repairs.

Taking a good look at the wiring on these old cars is really "job 1" to protect you're investment!

Nice Post!

73 Grandé
351C 2v
Now 4v Carb/Cam/headers/T5

Gasoline is for washing parts.
Alcohol is for drinking.
Nitomethane is for racing!

Work in Progress photos here:
Last Update: 4/23/16


OMG, that is ridiculous! It might be time to contact Midlife. May the force be with you. Chuck
Good god. Why was there solder all over the main wire??

If you don't have time to do it right the first time, you sure as Hell don't have time to do it right the second time.

Dutch uncle
That was their "splice" where they had the two other large yellow wires junction with the second small grey wire and the original main yellow wire.

1973 Mach 1 Q code 351 4V, 9A paint, standard interior, 3.50 rear, C6 trans.
Gotta love how some people do wiring at least they tried to solder it..Unlike mine which had a wire nut under all the tape..I could never understand whats so hard about making a proper splice..it's actually pretty easy..Maybe I should do a video on proper wire splicing..

Qcode351mach;192656 Wrote:Maybe I should do a video on proper wire splicing..

I think many people would appreciate that, Scott!


[Image: 6y14ea.jpg]

Project started 8-7-10
Completed: All new suspension, rebuilt 351C H Code bored .030 over with mild cam and intake, new 3.50 TracLok, custom exhaust system
Current "mini-project": interior upgrade Undecided
I absolutely love those splices and wire nuts. It's what keeps me busy on the weekends.

Ammeter wiring is extremely precise with respect to wire length and wire gauge, as the two sides tap into the main power harness at slightly different positions from the starter solenoid. This allows the small difference in resistance between the large thick wires and the ammeter's thinners wires to allow a small amount of the charging current to transit through the ammeter gauge itself. Although I can repair ammeter wiring, I will never create it from scratch, as I cannot measure accurately to less than 0.5 ohms without investing in a milli-ohmmeter, which costs lots of bucks.

The original poster's photos show the result of trying to create the wiring for the ammeter from scratch. If that headlight harness came in, I'd probably replace it with a good core from my stockpile. The underdash harness can be repaired easily enough.

Let me check your shorts!

[Image: Flamicon2.jpg]

[Image: oldfart.png]
That just may be the worst attempt at soldering I have ever seen
Midlife has my harness. From one corner of the country to the other. Get well soon, wires. Big Grin

1973 Mach 1 Q code 351 4V, 9A paint, standard interior, 3.50 rear, C6 trans.
Share Thread:  

Possibly Related Threads...
Thread Author Replies Views Last Post
  Ammeter Wiring Kilgon 14 616 02-11-2019, 01:39 PM
Last Post: Kilgon
  Factory Ammeter Troubleshooting/Diagnostic 72 H-code 12 1,930 05-20-2016, 01:40 PM
Last Post: KJM
  Ammeter block f117rt 11 2,228 11-16-2012, 07:17 PM
Last Post: c9zx
Wrench Ammeter wiring help f117rt 2 1,032 11-14-2012, 01:16 AM
Last Post: f117rt

Users browsing this thread: 1 Guest(s)