Charging Issue


Rebuilding a 1956 Mercury Monterey and had generator rebuilt, then rechecked, replaced new voltage regulator twice and made an all new wiring harness that is wired per owners repair manual. Also polorized generator to manual specs…charging system won’t charge. Any ideas? Thanks


Have you checked all ground connections?


Most generators must have some type of “field coil” voltage in order to work. It usually comes through the charge light or functional ammeter. If the light or ammeter is bad…the generator will not charge.


I don’t remember off hand if the generator for your car has the field grounded internally and the regulator connects the other lead to the armature terminal or if the field winding lead is internally connected to the armature and the regulator provides the ground, On the latter system make sure that the regulator ground is continuous to the generator

In either case, the residual magnetism derived from the polarizing causes the field current and the armature voltage to build as the generator “builds”. Once the voltage is high enough i.e. 12.5 volts the cut out relay closes; the armature terminal is connected to the Battery terminal; the battery starts charging; and the ammeter starts to show a positive current flow (or the idiot light is turned ‘off’)

If you have a VOM or DVM, with the leads disconnected from the regulator measure the resistance of the Field Terminal to Armature Terminal or Field Terminal to ground as appropriate to your application. The resistance should be basically zero. As the generator builds you should see voltage rise on the Armature terminal with the regulator in the circuit. As the generator starts to produce excess voltage or overcurrent, the Field terminal voltage should start to drop or start to rise appropriate to the system. At the same time the voltage drop across the Armature and Battery terminal should be close to zero.

Good luck on this. You will have a hard time finding an auto electrical technician who can trouble shoot this system. They will really be ‘grey beards’. I think the last cars I worked on that had a generator were a 1950 Dodge, 1951 Plymouth, a 1954 Plymouth, a 1957 International Travelall, and a 1957 Olds Super 88. I remember agonizing over the correct way to polarize the generator after a change.


57 Olds Super 88, one of my favorite cars.


This is from a 58 Ford but it should be identical to your vehicle.

You might want to peruse through this link just for fun.


You are trying it in the car with the engine running, right? With a known-good battery connected? A generator is fairly simple. For it to output electrical power, a voltage has to be applied to the field coil (which produces a magnetic field for the armature to spin in), and the armature has to be spinning. Provided the bushes and commutator are doing their thing, electrical power has to be output.

hmmm … well I’m no expert on 1950’s auto generators , not at all, but if I had this problem and a visual inspection didn’t show something wrong (like a brush was dirty or had fallen out, commutator fingers oxidized or dirty, etc), I’d probably see if there is a way to remove the battery and the voltage regulator from the circuit, in order to isolate it down to the generator itself. I’d probably remove it from the car and hand spin it on the bench, or see if I could configure something like an electric drill to spin it for testing purposes. It’s simple physics. If it has a magnetic field produced by the field coil, and the armature is spinning, it pretty much has to output something. In your case it probably is, but something is amiss with the voltage regulator or solenoid switch or maybe (this is nothing but a guess) there’s a centrifugal-force switch that isn’t making good contact.


What is the charging indicator on your dash instrument panel? Is it an idiot light or an ammeter? Are you getting 13.5 to 14.5 volts DC at the Bat terminal of the regulator with the engine running? If so and if you have an ammeter check the wiring to the ammeter, the ammeter itself, and from the ammeter to the battery. I have seen resistance in ammeters or the connection terminals that restricts current. Ohm out the path. A resistance of 1 ohm will cause a 1 volt drop at 1 amp current which would barely register on the ammeter.

Are you sure that you have the correct regulator? There should be continuity between the Arm terminal and the Fld terminal with all wires removed

With the engine running, measure the voltage drop from the armature post on the generator to the battery. Post that number on this site. In fact give us the voltage readings referenced to generator ground of the Bat terminal, Arm terminal, the Fld terminal, and the regulator base with the engine running. That will give us some information to contemplate.

BTW the 1957 Super 88 had the J2 RPO 371 with 3 two barrels. Had a lot of get up and go when urged onward Wish I still had that chariot in my stable.

Come on back ‘webdawg’. Hope to help


Mine was a 4 barrel, not the three deuces. I found the original window sticker. It had one of those 50 engines that Olds had to sell in order to race it at NASCAR. Of course it was detuned some for the street. A J2 could not keep up, a buddy of mine had one of those. In fact the reason I bought mine was because he got his and I liked it. Didn’t know about the engine when I bought it though. I found out about that later. I got it at an estate sale. A local stock car racer nearby recognized the car, he had worked on it in its earlier days.


Google “Full Fielding a generator” and see what you come up with…By connecting a jumper wire between battery + and the field terminal on the generator, the generator will produce maximum output. The test is RPM sensitive so fast idle is fast enough…If your generator responds to this, you know it’s good and the problem lies in the regulator circuits…