1948 P15 Grounding

[dbloss]

I recently acquired my grandfathers 1948 P15. It hasn't seen the road in over 15 years and has passed from my uncle to my cousin in the meantime. The engine was replaced by my grandfather many years ago with a P23 engine.

 

I am in the process of getting it running again and need help with the grounding. Currently the battery appears to be wired as 6V negative ground instead of positive. The negative battery cable is terminated to the engine block. The ammeter deflects negative when lights and accessories are turned on which indicates at least this was rewired. The regulator is a VRP-4501A. I have no spark and am trying to eliminate possible causes. This was supposedly a running vehicle when it went to my cousins in 1997.

 

Would they have converted to negative ground for a reason?  Should I be concerned and switch back to positive ground? Where can I find a electrical diagram for this car? Thanks.

[Plymouthy Adams]

there is no need for concern at negative ground...but if you wish to swap back to positive grounding flashing the regulator along with swapping the ammeter wires will be a must..also observe that the coil primary wiring should match whatever grounding you have your car orientated.  If negative ground the neg side goes to the distributor and + will be battery if Positive ground the + side goes from the coil to the distributor and naturally the - lead will get the battery while the coil will work either orientation the secondary voltage can be a bit less in output if improperly connected....also the points exchange metal for the contact surfaces and the deposit transfer will reflect the wear (pit and tip) to opposite contact points depending on what ground is used..

[_shel_ny]

This may help:

 

It says Dodge, but is a D25 which should be the same as a P15

 

Diagram posted in a previous thread courtesy of RalphD25cpe

 

 

EDIT:  and welcome to the forum.

Edited July 15, 2013 by shel_bizzy_48

[_shel_ny]

You may also want to post in the forum section rather than the "Technical Archives". Possibly more response.

 

 

http://p15-d24.com/forum/4-p15-d24-forum/

 

 

Edit: possibly mod would consider moving this to the p15-d24.

Edited July 15, 2013 by shel_bizzy_48

[fourleaf]

there is no need for concern at negative ground...but if you wish to swap back to positive grounding flashing the regulator along with swapping the ammeter wires will be a must..also observe that the coil primary wiring should match whatever grounding you have your car orientated.  If negative ground the neg side goes to the distributor and + will be battery if Positive ground the + side goes from the coil to the distributor and naturally the - lead will get the battery while the coil will work either orientation the secondary voltage can be a bit less in output if improperly connected....also the points exchange metal for the contact surfaces and the deposit transfer will reflect the wear (pit and tip) to opposite contact points depending on what ground is used..

 

First welcome to the forum! I am also running a negative ground system in my 48 P-15. I used the same wrining diagram that was posted and it went fine. My 48 also came like this and it was a pain to diagnose. Always ask these questions on this site because these guys have been around these cars and issues for a long time. I am really not sure why the last owner of mine went to negative either but i know i have to keep it in the back of my head with solving any issues relating to this topic on my P-15. Thanks