32 4-cyl alternator wiring help needed

[rbullockv8]

Converting my relatively stock 32 Model B 4 cyl to 12v neg ground with single-wire alternator.

I have a 12v resisted coil from Napa, 12v bulbs, 12v distributor condenser, etc. No electric to gauges to worry about except dash light. Need to buy a higher capacity ammeter than the original 20 amp.

I'm trying to use a new original wiring harness I already had, and I'm going a little crazy in my hot garage trying to figure it all out since the printed diagram doesn't match the actual loom wires exactly (I think the diagram is more virtual then actual). The truck has been apart for years, so no existing wires to trace paths.

Attached is the service bulletin wiring diagram for the 4 cyl. I've got most of it figured out except for replacing the generator with the alternator.

Questions:
1. Does the new alternator single terminal get all the wires in the diagram that lead to the generator cutout? That is the YB back to the ammeter; the YR to the main light switch BATT; and the Y to the 12v horn?

If so, does the alternator charge the battery through the circuit running back to the ammeter and to the + side of the battery?

2. My 20 amp ammeter has the pass-through type of connector, not separate terminals, but my wiring harness has terminal connectors. I assume most/all new ammeters will have terminals? Is a 30 amp ammeter enough? I have a Nu-Rex 12v neg ground alternator, but it's been years since I bought it and don't remember the specs. Probably 60 amp max output or something.

I think once I know what to connect to the alternator, I can use a meter to trace the connections through the wrapped wiring loom to make sure I've got it all straight.

By the way, if it makes any difference, I have the foot starter rod, not the pull cable, so my starter switch mounts on the rear of the steering box and has two heavy gauge terminals on the underside.

Anyone willing to jump in? Also, please...let's not hijack this as to why I should stay on 6v +grnd. :-)

Rich Bullock
Redding, CA

[old Tom]

uestions Questions, lets take them one at a time:

Questions: 1. Does the new alternator single terminal get all the wires in the diagram that lead to the generator cutout? That is the YB back to the ammeter; the YR to the main light switch BATT; and the Y to the 12v horn?

The main big single wire output lug could/would feed YES basically all (12 Volts) that was wired to the BAT side of an old Cutout Relay. That would be the LOAD (NOT Battery/Starter) side of the Ammeter,,,,,12 VDC to light switches BAT INPUT etc. Sometimes those loads are fed off the LOAD side of the ammeter but that's electrically the same as BAT on a Cutout Relay or the LOAD side of an ammeter. That's where the BAT on the cutout wires anyway but now the alternators main big output stud.

"If so, does the alternator charge the battery through the circuit running back to the ammeter and to the + side of the battery?"

The alternators charge gets to the battery to charge it VIA THE AMMETER. The LOAD side wires to the alternators output while the SUPPLY side gets to the batterys ungrounded post often where the big battery cable attaches to a starter switch or starter solenoids input. It needs wired at right polarity or would read bass ackwards.

2. My 20 amp ammeter has the pass-through type of connector, not separate terminals, but my wiring harness has terminal connectors. I assume most/all new ammeters will have terminals? Is a 30 amp ammeter enough? I have a Nu-Rex 12v neg ground alternator, but it's been years since I bought it and don't remember the specs. Probably 60 amp max output or something.

A typical new ammeter will have + and - terminals
which I call the LOAD (output and BAT on Cutout or new alternators output) and SUPPLY (input from battery) Sure ideally a 50 or 60 amp ammeter might be used but a 30 will suffice. It may peg for a short period after start up depending on battery condition. Trouble with a 60 is after start up the needle may not move much. A 20 amp may be a bit too small to handle an initial 50 or 60 amp surge but Ive used plenty of 30 amp meters on a 60 amp alternator never had a problem if you don't mind the needle possibly pegging after start up.


Anyone willing to jump in? Also, please...let's not hijack this as to why I should stay on 6v +grnd. :-)

If you insist lol your tractor your choice NOT any of ours

John T

[FlatheadTed]

on a stock loom /.harness on your model there is only one wire to the generator attach that to the alternator its next to the coil wire .Swap bat coil and amp gauge neg earth then you are good to go

[Charlie Stephens]

Originally Posted by rbullockv8

Converting my relatively stock 32 Model B 4 cyl to 12v neg ground with single-wire alternator.

….

2. My 20 amp ammeter has the pass-through type of connector, not separate terminals, but my wiring harness has terminal connectors. I assume most/all new ammeters will have terminals? Is a 30 amp ammeter enough? I have a Nu-Rex 12v neg ground alternator, but it's been years since I bought it and don't remember the specs. Probably 60 amp max output or something.


Rich Bullock
Redding, CA

I don't know about new ammeters but the correct ammeter for your 1932 truck should have 2 terminals and a 20 amp range. The 1933-34 trucks used the pass through wire and were 30 amps. One thing you can do to use the original ammeter is to run a by pass wire across the terminals. For your 30 amp loop ammeter just splice a short wire in to take some of the current around the ammeter. The amount of current going through the ammeter depends on the length and resistance of the wire you use. Now you will have the original looking ammeter but you will need to get used to the ammeter reading low.

Charlie Stephens

[rbullockv8]

Thanks, all. Very helpful. Now I just have to find a 30 amp ammeter with terminals. They make them for Model As. Anyone know if they are the same 1 7/8" size that the 32s take? I'll post over on the A forum, too.

[Charlie Stephens]

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Originally Posted by rbullockv8

Thanks, all. Very helpful. Now I just have to find a 30 amp ammeter with terminals. They make them for Model As. Anyone know if they are the same 1 7/8" size that the 32s take? I'll post over on the A forum, too.

Rich,

The Model A amp meter looks enough different from the '32 that I don't think you will like it. There is a picture in Snyder's Catalog for you to compare (http://www.snydersantiqueauto.com/se...&x=-553&y=-201). If you are worried about too much amperage through the meter do what I did and run a jumper wire across the two terminals on the '32 meter to carry some of the current and accept the fact that it will read low. I have never seen a 30 amp ammeter for 1932 and there is no reference to one in "The 1932 Ford Book". If you need a picture of a '32 ammeter (to compare with the one in the Model A catalog) there is a good one on page 6-6 of "The 1932 Ford Book".

Charlie Stephens

[koates]

Hi there, I would run with the original ammeter because most of the time that alternator will only charging 5 to 10 amps anyway. After cranking and starting the car the alternator will charge higher for a minute or two. It wont hurt the inductive type ford ammeter even if the needle hits the stop on the end of the dial. All the wires that were on the generator cut out (battery side) will now go onto the alternator main battery terminal. If the ammeter reads backwards, just reverse the direction of the wire going through the ammeter loop. When you work out the correct direction of that loop wire you can join the two ammeter eyelet terminals together permanently by soldering or using a 3/16 plated screw and nut with a shakeproof washer through the two eyelets and tape it up or heat shrink to insulate. Regards, Kevin.

[Charlie Stephens]

Rich,

Another thought. If the belt is loose enough not to destroy the water pump you will see a lot less amps than the alternator is rated. You might want to try it out before you worry too much about the amp meter. I may be conservative but I wouldn't peg the amp meter too often or for too long. An unrelated piece of advice is that the "Brite" bulbs from Ron Francis, wire-works.com, (800) 292-1940 , go right into your existing light sockets and provide excellent light.

Charlie Stephens

[rbullockv8]

Charlie and Kevin: Since my ammeter is a pass-through type and my wiring harness has heavy duty terminals soldered on, I was thinking running a new heavy wire through the pass-through and connect to each of the harness wires. Either of you see any issues with that? (There is no way to run the harness wires through the gauge pass-through without cutting off the existing terminal connectors). I guess (as Charlie suggested earlier), I could also run a jumper that DOESN'T pass through the gauge to bleed off some of the current if it pegs too often or long.

[Charlie Stephens]

Originally Posted by rbullockv8

Charlie and Kevin: Since my ammeter is a pass-through type and my wiring harness has heavy duty terminals soldered on, I was thinking running a new heavy wire through the pass-through and connect to each of the harness wires. Either of you see any issues with that? (There is no way to run the harness wires through the gauge pass-through without cutting off the existing terminal connectors). I guess (as Charlie suggested earlier), I could also run a jumper that DOESN'T pass through the gauge to bleed off some of the current if it pegs too often or long.

Maybe you could get a terminal block and run the two wires at the same time. I think I would just look for a '32 gauge.

Charlie Stephens

[koates]

Rich, What you have suggested sounds OK to me. Make sure your connections are clean and tight. Regards, Kevin.

[G.M.]

Why do you need a 30 amp meter?? Your truck is not going to draw anymore amps than it did before. The 30 amps comes in effect only if you have equipment drawing more then 30 amps. The 20 amp gauge won't burn out with a little more load on it. G.M.

[rotorwrench]

When modernizing to 12-volt negative ground you are altering the system so there is no relevance in my book for trying to use original equipment. If you notice, most modern vehicles with guages don't use an amp meter but instead use a volt meter. I'm not sure if there is one available that would look correct but there may be. Model A reproduction amp meters are crap. They aren't worth messing with. The OEM ampere meters for that time frame are getting harder to find and therefore more valuable for the purist restorer. As was already mentioned, a shunt will be needed for use of an ampere meter in a 12-volt system. We use a calibrated length shunt wire in the 12-volt helicopters and they work OK but you can seldom see what is going on with the system after the battery is charged back to it's normal capacity (the needle moves very little if at all even with heavy loads applied). The loop type (inductive) amp meter would be your best bet for that type of operation. It won't tell you much either but it will function. Replacement of the load wires with a single wire or terminalizing it with a terminal block to get your loop should work OK as was mentioned.

[rbullockv8]

I'll give the 20 amp gauge a try. Sounds like I can always change later if needed.

[Charlie Stephens]

Originally Posted by rbullockv8

I'll give the 20 amp gauge a try. Sounds like I can always change later if needed.

Rich,

How about "I can always add a jumper wire later if needed"?

Charlie Stephens