changing to negative ground

[janan5243]

After much research & trepidation, I finally had time to do some work on car. I read many posts about changing ground & flashing generator. Hardest part, which I suspected would be, was how to get to ammeter to reverse wires. after much inspection & contortion trying to get to the ammeter, we decided that the only way we could do it would be to pull the dash. Not what I really wanted to do at this time. Finally studied schematic to see where else wires could be gotten to easily. Discovered that one side went to battery terminal on starter solenoid & other side went to battery terminal on regulator. Switching those wires was a whole lot easier then pulling the dash or hiring "janitors in drum" to go under dash & reverse wires. Had to lengthen wire from regulator to reach solenoid. Soldered connection & heat shrink wrapped. Connected battery in new polarity. Started car & prepared to flash generator. Great happy news. Generator flashed itself & was charging. I know there is no logical explanation for this but car starts better & now charges at an idle. I,m going to check idle rpms with tach & dwell meter. Just an afterthought, as I've gotten older I've gotten much more careful about doing things like this. When I was younger, I would have jumped in instantly. would appreciate any comments on my method for reversing wires on ammeter.

[Young Ed]

You may find that some of the supply wires are now on the wrong side of the gauge. Without starting the car try turning on lights and see if it goes negative. Also does it go slightly negative with the key on before starting?

[janan5243]

I'll have to check that out. When I first turned key on, the gauge didn't do anything. When I started it, after a second it started charging.. If I remember the schematic, the only thing on the gauge was the cigar lighters.

[Plymouthy Adams]

if only thing on the gauge (am guessing you mean amp meter) is the cigar lighter..you need to readdress your wiring..

[janan5243]

I don't have car or schematic handy but all wiring is original except what I just changed. Cigar lighter is going to be rewired 12V with a fuse or circuit breaker. If I remember the schematic correctly the lighter was the only thing directly on the ammeter.

[DonaldSmith]

The cigar lighter wire should have been connected to the same post on the ammeter as the wire from the starter solenoid, so that the cigar lighter current would not go through the ammeter.  The other loads would be connected to the other post, so that their current would be measured.

 

For positive ground, the negative cable is connected to the large post on the solenoid, along with the wire that goes to the alternator.  The cigar lighter wire (along with anything else which is not meant to register on the ammeter) is connected to this same post on the ammeter.  

 

For negative ground, have the positive cable connect to the solenoid post (and the negative cable to the engine for ground).  To make the alternator read right, switch the wires at the ammeter posts.  Keep each group of wires together.  

[Don Coatney]

The job of the voltage regulator is to monitor the storage capacity of the battery and adjust the generator output to keep the battery voltage at the fullest. The job of the ammeter is to measure current flowing through it. Things connected directly to the ammeter will register such current flow with spikes both high and low. Things connected directly to the battery will not be displayed as spikes on the ammeter but will show as lesser changes on the ammeter gage as the voltage regulator does its job of maintaining the battery at the fullest charge.

[janan5243]

If there is a way to get to the ammeter on my car, I would be extremely happy to hear about it. It looks like that part of my dash is a separate piece but I didn't see any way to remove it. My ammeter is the top, left gauge, above the headlight & dash light switches. The ignition switch is below them. I would love to get in there to work on some other wiring. There is a mass of wiring below the ammeter from all the switches & I can,t even see the posts on the ammeter. I'm sure there is a solution that I just haven't discovered yet. The shop manual I purchased is really quite basic. If anyone can steer me to a better one, I would definitely buy it

[janan5243]

I sit here with plenty of egg on my face. I stand corrected on my recollection of the wires connected to ammeter. All other posters were correct, there are more than 2 wires. I was so focused on changing polarity I couldn't see the forest for the trees. That said, The wire from the bat terminal on the regulator goes to meter, from there to ignition switch & also thru 30A breaker to door switches & headlight switch. Wire from starter solenoid goes to meter & then lighters.  So discharge from lights, etc. does not show as a load. Regulator does tell me generator is charging as needed, dropping to slight charge after some driving. I will locate breaker & can correct that with a new junction point. I have disconnected the lighter from 6V & run a fused 12V line to it & powered stereo. Only problem is stereo does not turn off with switch. Just use stereo power switch. I want to install an alternator but have to peruse wiring changes since regulator will be removed. Hopefully someone on forum has advice on that. Thank God I like eggs.

[DonaldSmith]

A few years ago, I had a local auto electric shop put together a 6 volt positive ground alternator for me.  The rewired it for positive ground and put in something to keep it down to 6 volts.  They could more easily make up a 6-volt negative ground alternator.  (I still don't know why you are going to negative ground.  I'm missing something.)  

 

My wiring changes were simple.  

My starter solenoid was connected to the generator "A" terminal, so that the solenoid would be grounded when the engine was not running. So I just grounded the wire from the solenoid to the body.  (The body and frame have jumper wires o the block, for good ground connections.) 

The heavier, red wire at the "A" terminal went to the regulator, where a black wire ran to the ammeter.  I bypassed the regulator and connected the single wire from the alternator to the wire to the ammeter.  

There was a green wire from the "F" terminal of the generator to a terminal on the regulator.  I just disconnected both ends and abandoned this wire.   

[janan5243]

I went neg. grd. because I,m planning on using modern electronics in car. I plan to use original radio antenna with stereo. As soon as I plugged positive ground antenna into stereo it would burn it up. Original radios with mechanical vibrator would work either way.

[TodFitch]

I went neg. grd. because I,m planning on using modern electronics in car. . .

I have rigged a 6+ to 12- inverter/converter under the dash that can supply about 2 amps. I use that to the few modern accessories that I need/want in my old car.

[janan5243]

I have one of those also, just never installed it. I purchased a 12v HEI electronic ignition from another member last year & I don't believe one of those convertors would power it.

[janan5243]

because of my unorthodox method for reversing wires on ammeter, I've had some weird things happening. At first, the charging system seemed to work properly, even tho the regulator was not seeing the loads(I reversed the wires on ammeter by switching the regulator bat terminal with the battery terminal on the starter solenoid). Now the ammeter is pegged once the engine is above an idle. A headlight burned out & a brand new pair of halogen fag lights apparently burned out. I'm going to measure voltage with engine running & check points in regulator. Is there any other downside to leaving wires on ammeter as they were with a positive ground other than the gauge reading backwards? If I can figure out how to get dashboard loose, I could switch wires properly. There is no way to get to terminals with dash in place. That section of dash is a separate piece. I've asked for advice on getting it loose but no suggestions yet. I'm going to remove interior windshield trim to see if there are any fasteners there that when removed would allow dash to tip back to steering wheel to gat at wires & gauges, etc. Would appreciate any tips.

[DonaldSmith]

Several years ago, I replaced my dash with a re-woodgrained one.  The dash did not tip out like you would want, but came straight back, after everything was disconnected.

 

No easy way.  I did some major rewiring recently, with the front seat completely removed.  Still no fun, but I could lie on by back.  I added some mats over the sill, since I usually found myself half out of the car.

 

 Later, I re-doodled the wiring to the ammeter, with the front seat cushion removed and the exposed frame covered with a few layers of flooring mats, like the 2-ft squares with interlocking edges.  Not fun either, but I could lie on the front seat and still get my head below the dash.  I added terminal strips for the wiring connections, body to dash, engine to dash, etc.  I ran two heavy wires to the ammeter and made all the other connections at the terminal strips.  Now any future wiring issues would be accessible.  Here are the terminal strips:

 

  

 

Here is the back of the ammeter, before I simplified the wiring.  The post at the right is the power wire from the solenoid and the wire to the cigar lighter.  The post on the left powers just about everything else.  (The horn gets its power from the solenoid, so it is not on the ammeter, but who looks at the ammeter when blowing the horn?) 

 

 

(Notice the long screw with jam-nuts at the instrument cluster.  After working on the instrument cluster,  I had such great difficulty getting the original screws back in place that I used these long screws.  The jam-nuts leave just the right length of screw end exposed to secure the cluster, and the length of the screw gave me something to grasp and start into the threaded hole.) 

Edited September 27, 2015 by DonaldSmith

[janan5243]

Donald; thanks for the reply. The terminal strips is an excellent idea. My dash is so close to the firewall that with all the wires to the switch's & the ignition switch, I can't even see the terminals on the ammeter. What is your car? If I can get the switches & ignition switch out I would then be able to get to the ammeter with the dash in place. They are all directly under the ammeter.

[DonaldSmith]

I've got a 47 DeSoto.  Yours looks like a 49.  The dashes are very different.  Maybe someone else can chip in. 

[janan5243]

Yes, mine is a 49. The drivers half of dash is a separate unit that sticks out further than the rest of the dash. With the dash in place, it is physically impossible to get to the back of the gauges.I'm sure there is some way to get it loose to get at the gauges but I don't see it. I have asked several times on forum & looked on net without success. I believe my regulator is bad. generator puts out 7v at an idle almost 10v 0nce above an idle. that burned out one of my original headlights & the new foglamps I installed. Got them from taillightking.com. Really nice guy. He's going to replace bulbs for foglamps & only charge me for one + shipping.

[janan5243]

I,m reviving this post in hopes of getting help on wiring. I converted to neg. grd. Never thought about regulator. Put a set of 6V halogen fog lamps in.( That was after burning original fog lamps up by hooking to 12V ). 1st nite using them was great, next night turned them on, went out after 1 minute. got home & immediately checked them out. They were burned out. $60.00 down the tubes.. Called guy I got them from, He said I had to have a problem with the electrical system for both to go at same time.

Got my multimeter out, connected across battery, 7V at idle, just above idle, almost 10V. Now I knew what happened to new bulbs & also an original bullseye headlight.

When I first made change, system was charging normally but I guess regulator didn't like neg. grd. Got a dual grd. regulator from local rebuilder ( $68.00) but had to figure out if I had an A circuit or a B circuit generator. After finding tests on the net, I had A circuit. Decided to switch to a 6V neg. grd. alternator. Only $40.00 bucks more. Had a double pulley put on. It fit with stock generator bracket, used threaded rod with a third nut to hold alternator against front of bracket. Had to change belt tensioner bracket, guy at rebuilder shop gave me one he had that worked, no charge. Wired it up the way he & I thought it should be after much discussion. Turned key on, gas guage worked, ammeter showed discharge, turned key to start, nothing & gas guage would drop to no power position. All I can figure is that power is not getting start lug on solenoid. Alternator is a one wire with internal regulator.a wire from solenoid went to regulator arm post & back to generator thru that connection. What the devil am I doing wrong. Even tried jumping solenoid from battery terminal to start post, nothing. Car started & ran when I started this project.

 

I know I repeated myself on several items, just wanted it all in one post.

 

PS. AJ at taillight king.com  has all kind of vintage & new bulbs for all applications. When I ordered new bulbs he gave me one no charge. He didn't have to do that, it wasn't his fault.

Edited October 13, 2015 by janan5243

[Dave72dt]

All I can figure is that power is not getting start lug on solenoid. Alternator is a one wire with internal regulator.a wire from solenoid went to regulator arm post & back to generator thru that connection. What the devil am I doing wrong. Even tried jumping solenoid from battery terminal to start post, nothing. Car started & ran when I started this project.

I would suggest getting that original regulator out of the system. Chances are you have drained the battery with it hooked up. If your new 6v N alternator didn't come with wiring instructions, call the supplier and get them. Check the starter also. It may be a 12V version and won't like trying to operate on 6V.

[janan5243]

Regulator is only being used as a junction block, has no electrical function as it did with generator.

[DonaldSmith]

The wire from the starter solenoid to the generator is the ground for the solenoid winding.  When the engine is not running, the generator windings serve as the ground.  When the engine is running, they are not.  This is Mother Mopar's way of keeping you from grinding the starter when the engine is running. 

 

My 47 DeSoto has four posts on the starter solenoid.  The upper posts are for the solenoid winding.  The left one gets power from the starter button.  (Car left, not looking-at-it left.) The right  post goes to the generator.  When you have an alternator, ground this post, to complete the circuit and power the starter.   The left bottom post is for the battery cable.  The right bottom post goes to the starter windings.  (The Sisson choke is powered by this post; the choke partially opens when the starter is cranking.)  

Edited October 13, 2015 by DonaldSmith

[janan5243]

Donald; I saw that last night when I was trying to figure out what I had done wrong. I attached the wire to a lug on the regulator that, according to my tests, was grounded. Maybe it wasn't a good enough ground. I'll check it out tonight. I knew it had to be in the wiring. It's cool that way back then, Chrysler had a way to prevent the starter from engaging when the car was already running. Thank you. I'll post results later.

[Niel Hoback]

If you have a one wire alternator, you should not have your old regulator wired to anything.

How I did it; I mounted the 6 volt negative ground alternator and ran the one wire from the alternator to the ammeter in the dash. Then I ran a wire from the other side of the ammeter to the battery terminal on the starter solenoid.

All the wires on the mechanical regulator are disconnected and taped up.

Functional since 1998.

[janan5243]

Neil; My regulator is only being used as a junction block, no electrical function. As for my dilemma, it appears that my solenoid somehow died sitting there. The winding has continuity, it is grounded. I checked continuity to ground at all points, including the battery ground terminal. When I turn key on, gauges work. Start wire from switch has power when activated by switch. I supplied power directly to start terminal on solenoid, nothing. I jumped battery post on solenoid, starter spins. It doesn't make any sense. All I did was remove generator, install alternator & wire correctly, I think. I realized that, as Don posted, that wire from solenoid that went to arm post on regulator had to be grounded so solenoid would work. I hate to have to pull starter to find out I have a wire in wrong place. If I pull starter, I'm going to try to find a starter with the newer style solenoid since I have disabled the circuit that would prevent starter engaging if engine was running already. Thanks Don for pointing that feature out.