• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

Reversed polarity

Share this page

longbridgehealey

longbridgehealey

Obi Wan
Country flag
Offline
My BN4 was in storage all winter at a friends shop. Before I picked it up he pulled the battery and charged it. When he replaced it in the car he hooked it up as a negative ground. The car started and ran fine. I just discovered it today. What should I do? Have I reversed it to a negative earth? Have I burnt anything out? Could I be more confused?
 
You could keep it that way or switch it back, either way. Regardless, you should flash the generator so you know it will charge the battery. I went with an alternator, so I can't remember exactly how its done. A search here will give you directions though. The other thing to worry about is if your fuel pump is polarity sensitive.
 
Hi Greg, the fuel pump must be ok because I have driven it a couple miles. Thanks
 
The temptation is to change it back
 
Longbridge, At the risk of not being very accurate, if your generator was disconnected from the battery source for very long, like all winter with the battery disconnect switch in the trunk off, then the residual magnatism was probably very low and it probably won't need flashed. I think two things might be the case with your fuel pump. If it is working then I think it is probably a dual polarity pump, or if it is a single polarity pump with a diode, then you probably blew the diode out. If it has a diode that is now blown , the pump may work for a short while but probably won't last. I would take the pump apart to check the points and if a diode is present I would change it. I think most other things electrical in the car will work with either polarity. Dave.
 
This is a timely thread. Vette, you say that "most other things electrical in the car will work with either polarity." Someone recently told me that all one has to do to switch the polarity of the car is to switch the battery cables at the battery. But other sources (can't remember where without doing a search) say that one must make a long list of changes to the car to properly change the polarity. Can anyone clear this up? Is it only the fuel pump that may create issues with a polarity change?
 
Well Greg has suggested and rightly so to polarize the generator to be on the safe side

. Similarly, Vette has pointed out the potential for a fuel pump to work if the diode fails short circuit.

Consequently, verifying these suggested items should get you good to go

Additionally read Legal Bills post on this forum relative to reversing Polarity..
 
Last edited:
Am I correct in thinking that a pertronix ignition comes in positive and negative, and will only work accordingly?
 
All these aforsaid points are valid. I am not the expert here but I do have an electrical background but it was in construction not in solid state stuff. Healey Rick makes a good point about the radio. Back in the day if some of us youngins wanted to put in an "American" radio we would mount it so the radio metal enclosure would not touch the metal of the car. You would also have to isolate the antenna. Big Pain so I never did it to my car. But aside from the radio, let me just go thru my thoughts on the items. Oh yeh, also when I redid my car about 2 years ago, I put in an alternator and reversed the polarity. I installed two fuel pumps, bought a new one that was dual polarity, and USED MY ORIGINAL ONE THAT WAS MORE THAN 30 YEARS OLD. The original one then quit after about 100 or so miles. The reason I installed the old pump was to just see if it would work. It did, for awhile. I never reversed polarity on anything else. The wiper motor will work, the blower motor will work, the horns, the flasher, the gauges also. I did wonder about fuel gauge because of the direction of the magnetic windings thinking it would try to operate in the reverse direction, but while I was cleaning it, the windings all unwound, and I ended up rewinding it, but I put them back on the same direction that they were, and it works. But I did have to adjust it for accuracy. So I'm pretty sure the fuel gauge doesn't need to be changed either. So doing a generator flash and taking precautions about the fuel pump are the only things that I think need to be done. Dave.
 
I never used an electonic ignition so can't answer about the pertronics. But I imagine it would be polarity sensitive. But if you have one installed I guess you just proved it would work. I was just thinking about the coil. i am pretty sure that spark plugs to work better in one polarity or another, but I don't really know which that it. I seen many cars running with differnt polarity on the plugs and they run fine. But I just installed my coil according to the markings on the terminals. If one terminal is mark SW that one is for the wire coming from the Iginition switch.
 
then I have my answer. My pertronix is a negative earth model, so somewhere along the line I must have reversed the polarity and just forgot. Stupid as that sounds, it's probably the answer. My old friend Doug Reid installed the pertronix four or five years ago, and he probably reversed it then. I'm sure he told be and I just forgot. Thanks everybody for the help!
 
The Pertronix has different wire colors depending on polarity. Red and black for neg. ground. Black/white and black for pos. ground I believe.
 
Yep, that's how it's wired, and with black and red. I think I'm ok.
 
Thanks everyone, I seem to be ok.
 
I appreciate your situation. I know the feeling when my wife tells me "You should know, I told you, you just don't listen." I wish that were even mostly true. Now forget everything and enjoy your Healey.

Ray (64BJ8P1)
 
Back
Top