1 wire alternator on a 68 XR7

I am looking to install a 1 wire alternator on my 68 XR7 with a 390. Before I jump into actually doing it, I would very much appreciate anyone’s advice about doing so.

Before I start I have a few questions.

  1. Will my factory tachometer continue to work properly?
  2. Will I need to rewire the ignition?
  3. Will my amp gauge need to be upgraded to a volt gauge? Where is the best place to wire in a volt meter?
  4. My electric choke is powered from the stator connection on my stock alternator. What is the best location to acquire power for the electric choke?

Thanks everyone in advance,

Robert Seeds

I cant answer your questions but i hate 1 wire alternators…its about having to rev up a cold motor to get it charging. I put a 150 amp late modelalt on or 67 and it works great. If i remember corecttly , i purchased a kit that replaced the orig regulator and all thesystems worked as they should. Make sure you get an alternator,that has the plus terminal does not hit the motor mount. Them serpentine belt pulley just needed to be removed and replaced with the stock vbelt pulley with a slight amount of trimming

Several years ago I went through a major overhaul on the electrical system on my 68 XR7. The research I did at the time convinced me to stay with OEM style wiring on the alternator vs a one wire conversion. I did have my ammeter converted to a voltmeter, my tach updated and rally clock new movement (by Rocketman). I have not had to chase any electrical issues and car has run well. IMO with the Cougar wiring complexity, it is better to stay OEM and to keep things plug and play. Midlife is also a good resource to correct the harness “workarounds” you find in these old cars.

  1. The tachometer and alternator wiring are unrelated.
  2. No
  3. Yes, your amp meter will not be functional. A voltmeter needs power and ground to work properly. The yellow wire under the dash works well for switched 12 volts.
  4. The yellow wire under the dash.

I have a 1wire 150 amp alternator. I actually chose it over a 3G setup for simplicity and it looks at home on my engine. Bolts right up and comes with a vbelt pulley. Dont let the rpm charging startup scare you as its not as critical as you might think but is something to be aware of. Mine starts charging pretty much right away without any input from me. I run a full set of aftermarket gauges so I have a voltmeter with low voltage warning light set so if by some off change its not charging right away I can easily see that.

With this setup you do not need the old voltage regulator or any of the factory alternator wiring. I built all new battery cables(larger gauge) from the alternator, battery, engine etc. Its been a nice clean setup. I also did the same for my fathers 67 mustang. His has been great too. The 3G option is also a good option but it takes a little more install with wiring, doesn’t look as clean IMO, pulley changes and possible case modifications to fit your mounts. This however has a bonus of more availably of an off the shelf alternator if needed in a pinch but they are typically less then 100amps. You cant go wrong with either setup really.

By the way the stock wiring is only designed to take the OEM alternators which produce 38 or 42 amps. The big wire on the alternator is not big enough for anything more. Smoke and fire results when you do the wrong things.

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Thanks everyone. Once again you have provided great advice. I am going to go ahead with the 1 wire project. Thanks again everyone.

I agree with Royce’s comment about the original wiring capacity. The main feed (#37 black/yellow) wire is only 10ga. Note that for the 1967-68 Cougars, this wire is NOT fuse or fusible-link protected!
With turn signals, headlights, and A/C, the main feed wire is already at the capacity limit.