And since Masked Rider mentioned it, I think #10 may be a bit small. I would definitely go with #8 or even #6 if it will fit the ammeter. My truck's ammeter is fed with the original wiring, which is at least a #8.
If you find that the red wire becomes too warm under normal driving, I would upgrade it.

 

So if I splice into the lower post of the ignition switch (as shown on the wiring diagrams) do I still need to bring the wire back to the junction post or does this splice complete the circuit?

 

No splicing. One end of the red wire for the ammeter needs to be attached to the battery side of the solenoid and the other end to the junction post, not spliced in anywhere.
I have several after market wiring diagrams, and the ammeter wiring in their drawings doesn't match any of the trucks I have worked on. Eventually, I ignored the book to get the ammeter installed correctly; I really think the wiring diagrams you have are causing confusion.
The wiring procedure I gave out is the way Ford did it, as an add-on rather than an integral part of the wiring switch.
My advice is not to splice anything into the original harnesses, but leave the ammeter circuitry separate.

I think if you will run the red wire from the solenoid to the ammeter and back to the junction post, it will work out just fine.

 

There apparently are 2-3 ways to install the circuit, perhaps more??? Several years ago FTE member emailed a diagram of the circuit after I posted a similar question. Suggest do the research. Post a pic. As Banjo mentioned, using fuse has not been an issue over the past; however, I not having a clue how to run the circuit had concerns with running that many amp directly to the instrument so I went with a fuse purchased at local Napa auto parts store.

 

The diagram above is exactly how I am laid out except with a single post junction block as in the drawing and not the pictures.

 

Proof again a picture is worth a thousand words!

Dave's drawing (http://i300.photobucket.com/albums/n...os/Scan1-1.jpg) is the way I describe it, except that it shows the wires connecting behind the junction block instead of on it. But that is of no consequence.
One point to add to the drawing, to repeat, is that all the wires that used to be on the battery side of the solenoid belong now on the junction block.
The only wires on the battery side of the solenoid should be the battery cable and one of the wires going to the ammeter.

Best of luck, John this should help a great deal, and you will be very pleased with having a working ammeter!

John
(The other John, for anyone who might be confused.)

 

Yeah, I've seen a good many without that little gem. However don't think I'd be without one.
Both my 65's and the one 66', all sport that little device. Not sure the history on one of the 66's but it looks factory. I do know the history on the other two and I know for sure, that they are.
I've seen what can happen without it. ((((
BUT, as many of you have said, 'To each their own.' )

 

So, I've spent the day installing the Bronco gauge cluster and I have a few issues.

First, I followed the directions provided by banjopicker66 and others and did not splice into the factory wiring harness. I upgraded the wire from a 10 gauge to a 8 gauge, ran it from the battery side of the solenoid, through the firewall, through the loop on the rear of the alternator gauge, back through the firewall and terminated at the junction post. It took 14 feet of wire to make the loop but there is not much slack. If you plan to do this, purchase at least 15 feet of wire. Upon starting the truck, the gauge does "work" but upon adding a load (lights, turn signals, etc.) the needle does not move smoothly---it bounces between charging and discharging. If I use the choke to rev the engine, the needle will remain static but at idle it also bounces. I've checked all the connections and they are clean and tight. What have I missed? Any suggestions will be appreciated!

Second, I replaced the oil sending unit from the indicator light sending unit to the gauge sending unit . I removed the light and rewired the connections for the posts on the oil pressure gauge. Upon starting the gauge go to the maximum end of the range. I've also checked these connections and even switched them on the posts to be sure I did not have them crossed but still the gauge goes to high and stays there. What have i missed? Any suggestions will be appreciated!

Thanks in advance for all your guidance!
John

 

The sending unit for the idiot light, and that of the oil pressure gauge are different. I installed a 'T' connection and currently using both gauges.
Oil pressure gauge: posting link for pix only, may want to shop around. Suspect local auto parts should carry item?
Oil Pressure Sending Unit | Dennis Carpenter Ford Restoration Parts

Again for pix only: idiot light sending unit:
Oil Pressure Sending Unit | Dennis Carpenter Ford Restoration Parts

 

Thanks Dave, as stated in my description, I did replace the sending unit from the indicator light unit to the unit required for the gauge, just like the one fron DC Carpenter. The gauge is still pegged out. Any other ideas? Is there an easy way to test the gauge?
John

 

Seem to recall branching off the Constant Voltage Regulator, located on the back of the instrument panel, for both gauges.

 

Here is what I did for the oil pressure gauge exchange:

1. Replaced the sending unit to the large "gauge" sending unit.

2. Checked the wiring diagram for the gauge vs the indicator light.

3. Confirmed the wire colors are the same for light and the gauge.

4. Cut the indicator bulb away and installed wiring connections to attach to the gauge.

5. Wired to match the wiring diagram.

** I will check the instrument panel voltage regulator since I sued the one on the bronco cluster and not the one from my previous cluster. However, the gas and temp gauges are working **

Thanks again for all the guidance! John

 

Imagine goes w/out saying if the cluster is the plastic CC type adding a ground strap from the metal portion of the cluster to a good source of ground would not hurt, I picked a spot on the petal assembly bracket. Suggest check the CVR, should oscillate from between 0 to 10 volts.

 

I had previously added a ground from the gauge cluster to the metal dash structure when I first got the truck. I'll increase the ground wire size and see if that make a difference.

 

OK, update for today.

1. Replaced the ground wire from the gauge cluster to the truck with a heavier gauge wire.

2. Checked the Red/White wire from the sending unit to the gauge -- good continuity, no response on the test light so its not "hot".

3. Checked the Black/Green wire using a test light it is "hot".

4. Exchanged the Gauge Constant Voltage Unit with the one from my previous dash cluster -- I know this one was good.

** Still the "Bronco" oil pressure gauge pegged out high again **

5. Attached another oil pressure gauge to the dash wiring and it also pegged out high! **

So, the only thing let that I can think of is the new sending unit is "bad". Is there a test I can do for the sending unit?

Does anyone have any other suggestions?

Thanks in advance!!! John

P.S. -- on a side note, the new "alternator" gauge is working great -- as are the "fuel" and "temperature" gauges!!!