Mystery solved, thanks one and all. I'm always grateful for the wisdom found in the forum, and for the willingness to share it.
38 coupe, curious as to the level of effort required to run the wire in the other direction. If the ammeter is doing the opposite of what it reads, then it's charging and I'm happy. Also curious as to why there'd be a wire connected to Field if the regulator is no longer hooked up. Appearance sake? If you have an inop regulator you want to swap for this one, let me know.
Backstory: In April I found this '38 on Hemmings Classifieds listed by motorlandcars.com in Maine and after striking a deal had it shipped to WI. Here are photos of the car:
https://www.motorlandcars.com/vehicles/82/1938-ford-deluxe-convertible (I didn't pay that price, by the way). The prior owner is in his 90's and the '38 was apparently his pride and joy. I heard from Motorland that he was delighted that the car would be cared for and driven, and he even kicked in half the shipping cost after the deal was struck. That was a pleasant surprise. I've had a couple of enjoyable conversations with him since buying the car. He'd owned it for 23 years, and the owner before him had it for 20 years. The owner before him replaced the motor with one out of a '49 Merc, which I didn't know until I started looking through the big folder of ROs and other docs that came with the car. Amazingly, ROs over the years totaled nearly $27k, all mechanical repairs/upgrades with the exception of $3k for a new top and boot and $2k for reupholstery, doors & floor. Trans rebuild and clutch assembly, 12v wire loom & related upgrades, modern shocks, new brakes & lines, starter, u-joints, Pertronix ignition & related items, and numerous other expected repairs/replacements. I guess he just loved getting his car fixed up. All I've done is replace the '90's vintage Coker Classic bias plys with 6.00x16 Diamond Back radials. I won't drive any distance on old tires, having learned my lesson the hard way. The bias plys had been put on by the 20-year owner and looked practically new. Likely that in the past 43 years this '38 may not have been driven much at all, since the 23-year owner said he'd only put about 500 miles on it. An old repaint holding up fairly well, just oxidized. Haven't found any rust. Odometer shows 24.5k mi, but who knows.
I've had 26 wonderful old classics over the past 45 years, with the 8 remaining ones sold after I retired and we prepared to move to a place without a 60x60 workshop. I miss them all, but once we got settled I planned to find just one old car, not counting the '98 BMW Z3 I bought for my wife a dozen years ago. Coming across this Ford sedan convertible was an unexpected stroke of luck, in all respects. Feels like a reward for the years of buying cars that were sometimes not as advertised, but eventually selling them all in better shape than when I got them, always reasonably and with known warts fully disclosed. I've learned along the way that while there's very little that I might know about solving a particular car problem, there are people who know exactly what's needed. Thank goodness for forums, car clubs and the rare shops that appreciate old iron.
Only real issue with this '38 was getting a WI title. I submitted the prior owner's Maine registration to DOT in April, but the serial number was only 4 digits. The DOT counter person said those 4 digits were assigned to a '70's travel trailer. Didn't matter that the 2002 BOS showed that same 4 digits being the serial number. I still submitted the title request and paid the fee, hoping DOT would somehow resolve the issue and send me a title. That was some magical thinking. I eventually was informed that if I couldn't supply accurate serial number and purchase evidence I'd have to pay for a costly WI bonded title, meaning DOT wouldn't assign a VIN and clear title until a 5 year waiting period was over. Setting aside the magical thinking, I used this forum to learn where I could find the serial number, uncovered it on the frame rail and took a photo. I also discovered that the 4 digits were from the body number placard on the firewall, so I took a photo of that as well. After 3 or 4 DOT phone transfers, I was able to get to someone in the Vehicle Research Unit, the ultimate arbiters for issuing titles when complications have been identified. A couple weeks after supplying the VRU with the frame rail and body number placard photos along with a copy of the BOS from Motorland, I finally received a title with the correct serial number. When I was buying the car, I asked if the registered serial number matched what was on the car, and they said it did. Partly true, because it did match the body number placard. Even if I'd been smart enough at the time to realize that the car's serial number couldn't possibly be just 4 digits, would I have bought it anyway? For what I was able to get this lovely '38 for, yes indeed.