Wire Alternator
Dave Stribling
December 9, 2016

Ammeters and 1-Wire Alternators

I'm taking a fresh look at the old dash in my 1970 Mach 1. The ammeter never worked and I have an NOS ammeter ready to drop in, but I've since converted to a big amp 1-wire alternator. Is there a safe way to fuse and install a factory ammeter into this configuration? The internet is rife with folks who insist it should not or cannot be done, but I thought all of us could of benefit from the schooling of the masters and that amazing collective wisdom at MM.

Douglas Phillips
Pacific Grove, California

Because you upgraded to a 1-wire alternator, I would lose the ammeter entirely and go with a voltage gauge. If you read Jim Smart's article on the subject on Mustang 360 (www.mustang-360.com/how-to/interior-electrical/mump-1005-ford-mustang-instrument-panel-troubleshooting), you'll find out the ammeter was very weak from the factory and frequently burned out. The ammeter is live all the time, which means it can actually be a fire hazard. American Autowire states right in its instructions that the company does not support the use of an ammeter in its wiring harness upgrades. The 1-wire alternator manufacturers are very fuzzy about the subject.

With your 1-wire setup, you are probably pushing 100-plus amps. Remember, your original alternator was 38 to 55 amps. Even though it is somewhat protected from taking the full force of that alternator charging everything at once, things can go bad really quickly. With a voltmeter, you blow a fuse. The coil in the ammeter can heat up and catch fire. Yes, there are owners claiming they are running their ammeters with a 1-wire with no problems. Some of those owners have dead ammeters (and don't know it yet), and some haven’t lit up the alternator to its fullest potential.

If you do run the ammeter, take a look at the original wiring harness. If you are running the 1-wire to the original two-terminal harness connector, you should be OK. If you are running the 1-wire directly to the starter solenoid post (and then to the car circuits), the ammeter circuit may not work properly. The remote connection to the ammeter through the splice in the harness plays to the way the circuit works. You also should put an inline fuse on the circuit to the ammeter to be on the safe side.

Inline Six Core Plug

I have a 1966 convertible; 200ci six with a bench seat. I recently had the engine rebuilt, and I’m having a hard time finding a freeze plug for the cylinder head. Would you happen to know the correct size and part number? I’m trying to keep the car as original as possible. The shop where I had it rebuilt used a rubber plug, and I really don't like that. Please let me know, thanks!

Antonio Fierro
Via the Internet

The Ford service part number for the end plug is C8DZ-2026-A, and it is actually a 1 1/64 inch plug. There should be no markings on the plug, and it should be about 1/4 inch in depth. Green Sales (800-543-4959; www.greensalescompany.com) in Cincinnati, Ohio, has a ton of them. Give the company a call and they can get you set up with the correct plug. If you need the clean-out plug, it is 1 3/4 inches in size and the Ford number is C8AZ-2026-A.