1936 1602 v12 Not Charging: How to test generator

John,
Your 1602 has a 3-brush type generator with a cutout relay AND a voltage regulator. Look at the wiring diagram on page 90 of the Pierce Arrow Wiring and Tune-Up Guide (published by PAS) This is a very good reference. See PAS Service Bulletin 89-#1 for a short explanation of this regulator; “Hollander parts interchange manual lists the original relay-regulator unit used on Pierce- Arrows from mid-year 1935 models on, as an Autolite #40300, used on no other automobile vehicles.”
This diagram does show a field fuse in the regulator, which could cause some of the trouble you describe. Another problem could be the loss of residual magnetism in the field iron, which happens after sitting for several years – the remedy is to flash the field coil with battery voltage for a very few seconds to restore this residual magnetism.

My 1943 Motors Manual confirms that 35-38 Pierce did use the Startix and a 3-brush generator. The third brush set the output voltage of the generator and is typically adjustable around the armature to make this happen. The generator section does explain that (1) polarity does matter to the voltage regulator, (2) there are several types of regulators used on cars of this vintage (A) Light switch controlled step voltage, (B) two step relay control and (3) vibrating regulator, which rapidly steps the output up-and-down in response to battery voltage.

A quick search of the internet DID turn up a mechanical voltage regulator with positive ground that should work to confirm your system: The Ford 8N & 9N from about 1950 have this system and the regulator is still available from antique tractor supply houses. Not a perfect fit, but probably better than nothing to prove if your regulator is the problem.

The cutout relay is the other issue and that can be investigated by removing the cover and verifying that the coil is a complete circuit and the contact arm is free to move. Some people change this out to a large diode hidden in the original enclosure, but should not really be necessary.

Hope this is helpful

Jon, this will be but little help:  Autolite acquired Owen Dyneto in the late 1930s but seems to have maintained the Dyneto part numbers.  An Autolite-branded 40300 will serve just fine, as it’s the identical piece of equipment.  Actually, in mid-1934, Pierce began using Dyneto starters and generators, replacing Delco-Remy units, but there are some original 1935 Pierces which had Delco equipment from the factory, including Paul Johnson’s very original model 845.

The regulators on 1936-38 Pierces remained atop the generator.  I’m thinking that someone substituted a 3-stage regulator for the Dyneto, and mounted it on the firewall as is the custom for virtually all 3-stage regulators.  I think you need to look at a wiring diagram and trace everything out.  Which generator (Dyneto 3-brush?) do you have?  Or did some previous owner convert the generator to a later 2-brush system in conjunction with the installation of the 3-stage regulator?  That is, a holistic approach to the charging system (generator and regulator) is required, including an analysis of existing wiring against the factory diagram.

And do you still have the Startix?  That unit senses a lack of signal from the generator and automatically engages the starter–to respond to a stall.

For many years NAPA sold a regulator VR755 that was used by many mid ’30’s classics as a universal substitute for the wide range of regulators used on those cars. It mounts to the generator as original. Unfortunately they stopped producing them a few years ago and they are very hard to find now – a lot of people bought spares.  That specific regulator was originally used on some models of ’35-36 Chrysler products. It does not have the extra gen lead sticking out the side to connect the startix (it was optional on Packard), but the gen connection is made under the regulator so I think the extra connection could be made there. I have a generator with regulator from a ’33 or ’34 Packard that looks identical to my ’35 Pierce unit including the hookups, although the internals are actually a bit different. It would probably work, but much harder to find than VR755.

The picture is one I took of a ’36 Pierce which appears to have a NAPA VR755 regulator attached to the top of the generator, the tell tale being the nut on top of the can.

The first time my Packard quit charging (with basically the same 3rd brush setup and regulator as Pierce) it was the regulator, the second time a few years ago it was simply the 3rd brush was worn out. They are easier to find than regulators if that is the case.

If I remember right it was a bit iffy to diagnose statically, testing it would show continuity statically. Good luck.

I went through the same experience with my 36 several years ago. Problem was an improper regulator. A universal regulator will burn up you generator. Regulators are either A circuit or B circuit. I found the proper regulator at Steiner antique tractor parts. I charge at 7.1 volts with lights on at fast idle. Voltage output can be set while car is running. Amperage is set by moving the third brush. I f you want the info I can dig out the proper part number. Call me at 479 414 6107 if you need the info. I was in the dark for so long and even generator people didn’t know. All the people who knew this stuff in the day have been dead for 50 years. Regulator was about $40. This will fix it if generator is charging.