Positive to Negative Ground

[Andrew]

Well I am going to do it (from positive to negative ground) but I have been reading a number of threads and I am more confused than I was when I began.

First things first,

1) Disconnect the battery (turn 180 to get ready for hook-up)
2) Change the negative ground switch on my radio
3) Change my Amp gauge wires on back of gauge
4) Change the coil so that (-) connects to points/distributor
5) Do I have to worry about my Tach (this is a S3 positive ground car)
6) Hook up battery
7) Change Polarity of Regulator (short out A1 and F ?????)

Please tell me if I am correct in all of this guys.

Andrew

 

[Alpine Bob]

Andrew,
When I changed over mine, I had to change my tach. If you look at the tach it will say Positive or Negitive, so I would think your answer would be "Yes, worry bout your tach"

 

[Tom H]

I don't know what you mean by "change the negative ground switch on my radio". If you have an original Pos Gnd radio, you pretty much need to change the radio. There is no convenient way to switch the radio from Pos to Neg Gnd because the antenna uses a shielded wire in which the shield is connected to the radio chassis, so the chassis will always be grounded and when you change battery polarity this will apply Neg V to the radio chassis whereas it wants Pos polarity. It will not work and will likely ruin the radio.

Or do you mean you have a radio that has a switch that allows you to change from Pos Gnd to Neg Gnd? If so, that simplifies the radio issue. That's an uncommon radio.

You also need to change the polarity of the Tach. There are several good articles with pictures and drawings on how to do this.

You need to change the polarity of the Generator, not the regulator.

Tom H

 

[Andrew]

Hi Tom and Bob,

Thanks for the information.
I have an original PYE radio correct for S3 and it has a pin-out type of a plug that can be switched from Positive to Negative ground. So I will make this switch to protect the radio. I read an article about changing the polarity of the Generator by shorting out the terminals at the regulator (A1 to F). Is it better just to short out the two leads off of the generator?
As for the Tach, should I just try and find a SV Tach or is the change easy?

Thanks,
Andrew

 

[jumpinjan]

I don't think you can reuse the battery, and you might need to get another size 24 with reversed polarity on the posts. I'm pretty sure the cables will not stretch. I remember the battery to be a glove fit to the cables.
I have a reversible ground radio that I purchased in mid '70s. There is a switch on the chassis, that selects either + or - ground.

 

[SIVAllan]

I don't think you can reuse the battery, and you might need to another size 24 with reversed polarity on the posts. I'm pretty sure the cables will not stretch. I remember the battery to be a glove fit to the cables.

Kill the battery stone dead and recharge backwards...??

 

[Andrew]

Ok, one thing I can say for sure......Allan has a great funny bone!
Thanks for the chuckle.

The radio will work fine as I have set it for negative ground.
The Tach I am sure will work as the S3 is mechanical is it not?
My battery will work...it just fits in sung as a bug. I have cables from a SV so they should work. I think the only other thing I have to address is my S3 clock. I don't think it should be an issue as it is not in working order. Are there any issues with leaving the clock connected as original?

How can I be sure that my generator is producing a sufficient amount of power? Please treat me like I know zip in this regard. The last think I want to do is fry something.

Thanks for the help guys.
Andrew

 

[mxp01]

Andrew,
If the Tach is machanical it will use a cable much like a speedo, The clock I beleive will not work,To be safe disconnect. Once the Gen is repolerized take a voltage reading, 14 or so is about right when running.(ignition light will also go out)
I just did this over the fall, i also went to an alternator, much more peace of mind, the over all job took about 3 months.
Also one other thing, when I did this nowhere mentioned anything about the Voltage Stabalizer under the dash for the fuel a Temp guage. I had had a aftermaket one I installed and that one fried!!! It was not from VB or SS, it was homemade. I changed it out with a Neg Earth and all was good. My point is i'm not 100% sure if the stock VS will work, But I think Tom or Nick would have the answer to that.

Good Luck
Cade (Mikes Son)

 

[V_Mad]

Yes the stock VS will work. Like the indicator flasher unit, it has a heated element that doesn't care which way the current flows.

Hi Andrew. The clock will be polarity sensitive, so dont try reversing it.

To check the generator output, just watch your ammeter after start up, and it should show a healthy charge at about 1500 rpm. Switch some loads (headlamps) on to check that it still copes OK.

 

[tony perrett]

Do the benefits of reversing the polarity justify the hassle?

 

[Tom H]

Tony, good point. I see no advantage to polarity change unless and because you switch to the better charging capability of an Alternator.

I think the S3 does not use a Voltage stabilizer for the gauges. If there is not one there originally, then none is needed now. If you add a VS to a system that had none, you will have less voltage applied to the Temp and Fuel gauges and they will read low, unless you also change the gauges and/or the Temp and Fuel sensors. I do not know which or if both were changed. I will check my S3 schematic later to see if it had a Stabilizer. If it does have a Stabilizer, It is not polarity sensitive and need not be changed.

I am 99% sure the clock is not polarity dependent. I KNOW mine in my SV is not. Most of these clocks used a "pendulum" powered by a magnetic coil and the rotating "pendulum" simply closed and opened a contact once per second to advance the mechanism of the clock. if this is the type then the coil is not polarity dependent. But since it's not workibg it may be simplest to not connect it.

You can easily look to see if the tach is mechanical.It will have a speedo type cable coming from the base of the distributor. If it is electronic then it is not very hard to change polarity, but it does require dissasembly = removal of the innards from the housing, unsoldering a few wires inside and resoldering those wires to different positions, and then reassembling.

As Tony suggests - let me ask - why are you changing to Neg Gnd?

Tom H

 

[Andrew]

I hope to do this on the weekend after I get caught up on things.
Is there anything I have to do to the smiths heater blower?
Should I change the leades for the smiths fan or is it grounded through the fan motor?

Hi Jan,
I know my battery will work as I have put it in the box the wrong way this spring and had to change it around.
I understand that the posts may be an issue but I have the cable connectors off of a SV that I hope will work.


Cade,
Can I take the voltage reading off of the regulator, what connectors off of the regulator do I use? I know I can repolerize the generator off of A1 and F but connectors can I use that would make it easy. Can I run the car without the Voltage Stabalizer?

VMad,
I don't think I will have to worry about the Tach as it is mechanical.
I will take the leads off of the clock to make sure I don't have a melt down.

Thanks for the help guys.
Andrew

 

[Tom H]

No need to change anything on the blower motor (or the starter). Both of these use series wound motors which go in same direction regardless of polarity

Tom H

 

[napa 1]

Andrew, I'm suprised you're finding time to do all this, aren't you up to your elbows in hood motif plans and molds, etc? (I know Scott's really anxious to get one.)

 

[Andrew]

Work, work, work

Hi John,

Rumor is that the only hood motif Scott is interested in is one with a smile and bumps in all the right places. I would hate to start something here but I hear that he is even taking pictures and posting them on the forum. I am very busy but I hope to get the chance to do this change on the weekend. Who knows, I may even one up Scott and do a flash or two (and post pictures).

Andrew

 

[mxp01]

Andrew,
You can take the reading from the Regulator, the A1 and A. The way I repolarized my Gen was I took the lead off my Gen and tapped it on the Field post on the Gen (you will get some sparks, that's ok). If you do have a VS yes you can run the car without it, your fuel and Temp just won't work. The only problem I had with the change from Pos to Neg is I could never get my Voltage Regulator to work correcctly again or others that I bought. Thats why I went to an Alternator with an internal Regulator.

good luck

 

[Andrew]

Ok,

Thank for the help guys. The change was very smooth; it took me about two hours to change things over. Everything seems to be working and my reading at A1 and A (at the regulator) is 13V.

The only gauge that is not working as it should is the AMP gauge. It sits around "0" and jumps a little to the positive side when the car is running. I put the blinker on or the lights it is seems to read a draw dropping a little below “0†and then regaining, but I don't think it is showing as accurate as when it was negative ground.

The only alteration I did with the AMP gauge was to reveres how it was hooked up. Is this correct? I have another Smiths amp gauge that I will try this weekend to see if it will work better.

Thanks again guys.


Regards,
Andrew

 

[Tom H]

Andrew.

Turn the car off and then turn on the lights. You should see the Amps gauge go to the - side. Then turn on the blower and then the wipers. It should read even more -. If it does that, it seems to me it's working correctly. Then turn off the lights etc, and start the car. The gauge should go + a lot for a few minutes as the battery recharges (most of the lost charge went into the starter motor, the lights etc don't take that much in a few minutes). After a few minutes of + indication the meter should gradually move back to center as the battery gets fully charged. Once the battery is fully charged, there should be little movement of the Ammeter.

Tom

 

[Andrew]

Positive to Negative

Hi Tom,

Thanks a bunch for the note. It looks as if all is "GO", did the test and I am off full speed ahead into the world of Negative earth. Now I can use my 12V cooler, inverter, phone, CD player and other goodies with little or no fear of the fireworks of past experience.

Andrew