Got my battery hooked up to my 48 DeSoto, but starter won't crank.

[marcapra]

I just rewired my dashboard with a new harness and have begun to connect it to the car.  The starter wires, generator, coil, distributor, horn relay, regulator, transmission relay, are hooked up.  So the car still needs a lot more wires to be connected.  But i thought I would get in and see if anything was working.  The dash lights would not light up except for the left turn signal, which glows a colorful orange.  I don't have the turn signal control installed yet.  So I thought maybe the starter needs the ignition to be on to crank.  So I turned on the key and pushed the starter button.  Nothing.  But the clock started to tick.  That's not supposed to happen.  So now I realize that the clock is not supposed to connect to the ignition switch.  My DeSoto friend told me his clock connects to a terminal on the headlight switch.  I tried the windshield wiper switch, and it started to work with the key on.  So something with the starter must be hooked up wrong.  The starter worked when I hot wired the engine last summer and the engine ran fine.  My DeSoto buddy told me something I would never have known just by looking at the wiring harness.  It looks like the brown wire that goes from the top left terminal of the solenoid goes to the A terminal of the generator.  But he said no, it goes to a grounding screw on the generator between the A and F terminals!  There was a bracket for a missing radio resistor mounted there.  I guess I will just have to use my continuity tester and trouble shoot my wiring until I find the probelm.  

[Oldtech]

If you have the ORIGINAL solenoid - square with the 2 small terminals, one is the power and one is a ground. The ground one goes to the A terminal on the generator.  The ground path is THROUGH the generator. The Idea is that once the engine is runnng there will be 6 volts on that wire so hitting the starter button accidentally won't engage the starter.   The yellow one is from the starter button which is supposed to get it's power from the hot side of the fuel gage. If you have no start on the button the gage likely isn't getting power, OR the brown wire isn't grounded.  A test light should show you. 

You could just ground the brown wire as your buddy said, but that defeats the "safety" function. 

Edited June 6 by Oldtech (see edit history)

[marcapra]

Yes he talked about that feature of protecting the starter from accidentally engaging with the engine running.  So I guess my wiring diagram is correct.  I will put the brown wire back on the A terminal then.  Do you know what terminal of the headlight switch the clock wire goes?  Thanks for your expertise!  Marc.

Edited June 6 by marcapra (see edit history)

[CarlN-NDC]

I was the one who gave Marc the suggestion of moving the grounding wire to the grounding screw on the body of the generator.  That is how the brown ground wire is routed on my 1948 DeSoto.

 

I believe the majority of the wiring in my 1948 DeSoto is still as it left the factory.  The original owner of my '48 DeSoto parked it sometime in the early 1960's due to a blown head gasket.  It was stored in a not so weather tight garage until I purchased it in September of 2020.  I am still in the early stages of restoration and the engine the rusted stuck.  But my point with that statement is that there hasn't been a ton of hands or teenagers hacking it up trying to get it running again throughout the years it was sitting.

 

Maybe I was incorrect with the advice I gave to Marc.  I do know that the voltage regulator on my DeSoto was replaced at some point in its life.  So I suppose it is possible the mechanics had an issue getting it to start back in the day, so they bypassed the grounding through the generator by simply connecting it to the ground screw on the body of the generator.

 

One detail worth mentioning, at least on my factory wiring harness, the ring terminal end of the brown grounding wire on the generator side is of a similar size as the armature ring terminal.  The field ring terminal is noticeably smaller/narrower.  If the brown wire is just a ground connection, the ring terminal shouldn't need to be the same size as the armature terminal.  Except, if the ground wire is suppose to go to the body of the generator, it would need to be a bit larger to create a solid ground connection to the body of the generator since it is not directly attaching to a terminal post.  (If that is correct.  Maybe I am wrong, I don't know everything!)  

 

Additionally, something I noticed while looking back at a previous thread of Marc's, the Armature and Field wires are on the wrong terminal posts.  Theoretically, this shouldn't prevent his car from starting, but I wanted to point it out to avoid a potential charging system problem after he gets his car started!

 

To add to the confusion, I believe the factory wiring diagram is incorrect and has the A and F terminals flipped.  At least on all of the MoPar generators I have seen, the Field terminal post is on the left and the Armature terminal post is on the right.  The factory wiring diagram shows the inverse of this.  Unfortunately, this isn't the first time I have seen a factory MoPar wiring diagram be incorrect.

 

Below are a couple pictures from my 1948 DeSoto, along with what I believe should be corrected as far as the generator wiring is concerned for Marc's DeSoto.

 

Here is a view of the front third of my engine. (Sorry, I know the picture quality isn't the greatest, this is from several years ago.)

 

Here is a close-up view of my generator wiring.  I included both a non-edited and an edited version with color coding.  I know it is difficult to see, but the brown grounding wire runs under the armature wire.  Notice the size of the ring terminal for the grounding wire.

 

Here are two pictures that Marc previously posted that I edited into one photo for easiest viewing and I added color coded arrows for what I believe is correct.

 

 

As for the clock wiring, I will try to get you a picture for how/where specifically the clock wire is connected to the headlight switch on my 1948 DeSoto when I get home from work this evening!

[marcapra]

I looked at a Chrysler shop manual and in the pre-war cars the brown wire does not go to the generator A terminal, but goes to the A terminal on the voltage regulator.  So it seem like the A terminal functions as a ground.  It seems odd that Chrysler would print such a confusing wiring diagram over several years and different makes.  Is there a definite way to tell if a terminal is the Armature or the Field and prove the book wrong?

[TerryB]

Three wires on the generator and the brown one goes to ground.  That is an externally grounded generator.  Some generators ground via the metal case and the bolts that hold it on the engine and therefore have no third wire.  Armature is the output of the generator and current /voltage to the field terminal on the generator controls the generator output.

Edited June 6 by TerryB (see edit history)

[marcapra]

So do you agree that my generator is not wired correctly.  Is the A terminal toward the back of the generator?  

[TerryB]

29 minutes ago, marcapra said:

So do you agree that my generator is not wired correctly.  Is the A terminal toward the back of the generator?  

Did you see any A or F letters on the generator case?  If not you have to remove and open the generator to positively the armature and field terminals.  I wouldn’t go by just the drawing. 

[JACK M]

10 minutes ago, TerryB said:

Did you see any A or F letters on the generator case?  If not you have to remove and open the generator to positively the armature and field terminals.  I wouldn’t go by just the drawing. 

This is what I was thinking.

Maybe a little steel wool or the likes to see if that case has some light stamping on it.

[Fordy]

I may respectfully suggest that the car be either taken to an auto electrician or the OP pays particular attention to the fire extinguisher thread.

Steve

[CarlN-NDC]

Just to be clear, I believe there are two issues being discussed here.

1.  Identifying which terminal post is the Field terminal and which is the Armature terminal.

2.  The brown grounding cable coming from the starter solenoid and where the correct mounting location should be on the generator.

 

3 hours ago, TerryB said:

Three wires on the generator and the brown one goes to ground.  That is an externally grounded generator.  Some generators ground via the metal case and the bolts that hold it on the engine and therefore have no third wire.  Armature is the output of the generator and current /voltage to the field terminal on the generator controls the generator output.

^ Respectfully, I have to disagree with your point about the generator being externally grounded.  These 1940's MoPar generators are grounded through the generator bracket and do not require a third/dedicated grounding wire.

 

On my 1941 DeSoto, which is in running condition, it only has two wires going to the generator.  1. A 16 gauge green wire for the Field terminal (left terminal).  2. A 10 gauge red wire for the Armature terminal (right terminal).  It uses an Auto-Lite GDZ-4801A generator, which is the exact same generator as on my 1948 DeSoto.  According to my MoToR's manual, a GDZ-4801A is the correct generator for both a 1941 and 1948 DeSoto.

 

This brown cable we are also discussing is just a grounding cable for the starter solenoid.  My 1941 DeSoto does not have a starter solenoid or brown grounding wire, as it has a foot pedal starter and not a starter button.  Point with that being, my 1941 DeSoto runs and charges correctly without a third brown grounding cable using the identical model generator.  So I do not believe the brown wire is necessary as far as the generator's function is concerned.  But it IS required for the starter solenoid to function correctly.

 

The body of the generator on my 1941 DeSoto is stamped with an "F", "G", and "A" next to their corresponding terminals.  The Armature terminal post should be slightly larger compared to the Field terminal post.  I don't know if this if universally true for all 1940's era MoPar generators, but at least on my 1948 DeSoto, the Armature terminal post uses a 7/16 nut and the Field terminal uses a 3/8 nut.

 

Picture from my 1941 DeSoto engine bay for reference:

[TerryB]

Yes, I was thinking of some voltage regulators are grounded at the generator.  My mistake.  You are indeed correct about the terminal size as an identifier.  The field is usually the smaller terminal as you mention.  The armature has to supply much higher current and needs a larger wire and thus a larger terminal to handle this higher current.

[Oldtech]

3 hours ago, TerryB said:

Yes, I was thinking of some voltage regulators are grounded at the generator.  My mistake.  You are indeed correct about the terminal size as an identifier.  The field is usually the smaller terminal as you mention.  The armature has to supply much higher current and needs a larger wire and thus a larger terminal to handle this higher current.

Yes, the A terminal will be the larger one.  You should be able to fifure it out from here. If it were me... I would just ground the brown wire,  If you want, play with the "safety" system of grounding through the armature after it's all up and running.

[marcapra]

It's wierd that the Chrysler Corp. would get the wiring diagrams wrong on every shop manual and printed source, prewar and postwar, that I have found.  None of them show the F terminal at the front and A terminal at the rear.  That probably confuses a lot of restorers!  

 

Update,  I just looked up the blow-up of the generator in the 1948 DeSoto Parts Book.  It shows that the front stud, which the book calls the bushing, is the Field terminal and the back bushing is the Armature terminal, just as Carl said.  Good work Carl!  I never would have caught that.  The wiring diagram is backwards on this detail, I guess.  That's crazy!  

Edited June 7 by marcapra (see edit history)

[m-mman]

41 minutes ago, marcapra said:

It's wierd that the Chrysler Corp. would get the wiring diagrams wrong on every shop manual and printed source, prewar and postwar, that I have found

Wiring diagrams are 2 dimensional representations of a three dimensional environment.
The color and terminal connections will be correct BUT the physical locations may not be as seen in reality. They are maps, not photographs.  
 

Example all of your wire looms are round bundles, none of them are flat like shown on the diagram.  The diagram might show a red wire next to a black wire, but if you cut into the bundle you might find that the red wire is actually running next to a blue and green wire and no where near the black wire.  
 

The diagram posted by Carl N NDC, clearly shows the red wire going to an armature and the green wire going to the field.  Which terminal is on the left or the right should not be relied on from the diagram. 

The requirement of placing the lines on the page and illustrating which wires cross over each other and which wires are connected means that it might not be possible to illustrate the left and right sides as they exist in the automobile. 
 

The various gauges, switches and bulbs are certainly not laid out on the diagram exactly as they are when they are installed in the dashboard. Liberties have to be taken to make a paper representation.  But the connections between each end of a particular wire will be correct. 
 

Example: Connecting the battery cables would be performed properly by following the + and the - as shown on the diagram to power and ground and not just looking at the right and left side of the battery in the diagram. 

[marcapra]

That's true, but why confuse things by placing the A terminal in front of the F terminal when it should be the other way around.  You don't have to have a 3-D map to show that.  Anyway, in addition to proving the diagram is backwards, I shined a strong light on the generator and saw the F terminal in front, then the G terminal, then the A terminal in back.  So I changed my wires to the new locations.  Getting back to the problem in the original post, I hooked up a remote starter cable and was able to crank the engine.  I was going to start the engine that way, but now I have a problem with a badly leaking lower radiator hose, the one that comes out of the lower tank of the radiator.  I can't fix it by tightening the clamp, so I will be looking for a new hose.  

[m-mman]

47 minutes ago, marcapra said:

That's true, but why confuse things by placing the A terminal in front of the F terminal when it should be the other way around.

With no belt shown on the generator in the wiring diagram you really don’t know which way the generator is facing. So it might not be the other way around……

Again, wiring diagrams are showing point to point and connection to connection, everything else is just for a little orientation.  

[Bloo]

No mechanic would have given that a second thought in 1948. They would have just connected the big wire to the "A" terminal. We obsess over things like this now, but back then every car had a generator, and the charging current came from the armature, and that was that. Today sometimes we find things completely missing from manuals that nobody thought to put in because it seemed obvious at the time what you should do. The world has changed, and sometimes we have to do archaeology and relearn the ways of the past. If you don't let it get to you, it can be part of the fun.

 

[c49er]

Ok...now on to Marc's next question on his DeSoto.....

[JACK M]

10 hours ago, marcapra said:

I shined a strong light on the generator and saw the F terminal in front, then the G terminal, then the A terminal in back.  

Exactly why I carry a flashlight on my belt along with the Leatherman.

Old eyes seem to need as much help as we can give them.

[marcapra]

I'm wondering if it would be a good idea to go to a modern flexible hose to replace the leak prone three part hose of the original?  I'm thinking of trying one of these as a possible substitute if I can find one with a 1.5" I. D.  

Edited June 7 by marcapra (see edit history)

[TerryB]

3 hours ago, c49er said:

Ok...now on to Marc's next question on his DeSoto.....

It takes a community to raise a DeSoto, or something close to that old adage!

Edited June 7 by TerryB (see edit history)

[marcapra]

I went to NAPA and they had the perfectly sized radiator hose for me that looks just like the one above.  I took it home and couldn't believe how easily it fit my DeSoto.  It slid right on and was the perfect length!  I tightend the clamps and filled the radiator with water.  No more leaks!  if anyone else is interested the part no. is Napa  FF221 and cost $22.99.