TR2/3/3A 56 TR3 - Convert to Neg Ground or Leave As Is

[jfarris]

I know this is like asking, "what type of oil do you use?"
Originality doesn't bother me - see later comments.
I would like to convert to center and side brake lights with turn signals remaining in tail lights. It appears this will be easier if I convert to negative ground. Correct or not?
Later comments - I am about to get a speedo and fuel gauge rebuilt - do they care if pos or neg ground?
If the generator failed tomorrow, I would probably replace with an alternator.
If I had an alternator, I would add Halogen headlights.
If necessary, I would add an electric fan.
Thanks in advance!

 

[TR3driver]

I know this is like asking, "what type of oil do you use?"
Originality doesn't bother me - see later comments.
I would like to convert to center and side brake lights with turn signals remaining in tail lights. It appears this will be easier if I convert to negative ground. Correct or not?

Guess it depends on how you plan to do that. I built my own conversion, which does not care about polarity. But if you want to use one of the aftermarket kits, it probably will require negative ground.

Later comments - I am about to get a speedo and fuel gauge rebuilt - do they care if pos or neg ground?

Nope, not at all unless they are being converted to electronic. The originals don't care.

If the generator failed tomorrow, I would probably replace with an alternator.
If I had an alternator, I would add Halogen headlights.
If necessary, I would add an electric fan.
Thanks in advance!

Positive ground alternators are very rare (although they do exist), so you'd probably want to go negative ground for that. The fan probably will "care", but just needs the leads swapped to run either positive or negative. (But if you use a solid state fan controller, it may have a preference.)

Personally, I prefer negative ground (and that's the way my 56 is wired). But other than the alternator and any other electronic devices you might add, it doesn't make a great deal of difference. I just like having it the same as the other cars (including the later negative ground Triumphs).

Boring anecdote: Many years ago, a buddy and I took a long trip in our LBCs. We temporarily installed CB radios so we could chat while on the road. His CB antenna had a clamp that fit nicely on the rear bumper of his MGA. Worked great for the first few days, then suddenly his cockpit filled with smoke! Locked the brakes, slid to a stop, "Now where's that dang wrench!". He got the battery clamp off before it actually burst into flames but the wiring harness was a charred mess. What happened??? Couldn't be the radio, it had an in-line fuse that didn't blow.

Anyone want to guess?

 

[CJD]

If keeping it original is not an issue, an alternator produces more power more efficiently. The only gage that cares about polarity is the ammeter. I don't think the tail light conversion will be difficult for either polarity.

 

[Bremer]

Boring anecdote: Many years ago, a buddy and I took a long trip in our LBCs. We temporarily installed CB radios so we could chat while on the road. His CB antenna had a clamp that fit nicely on the rear bumper of his MGA. Worked great for the first few days, then suddenly his cockpit filled with smoke! Locked the brakes, slid to a stop, "Now where's that dang wrench!". He got the battery clamp off before it actually burst into flames but the wiring harness was a charred mess. What happened??? Couldn't be the radio, it had an in-line fuse that didn't blow.

Anyone want to guess?

Tell us, what was it?

 

[toysrrus]

Lightning struck the antenna?!?!?!?!?!?!?

Russ:rolleye:

 

[CJD]

Bet the radio chassis was negative grounded, without a fuse to that, but the antenae sheild was clamped to the positive grounded bumper.

 

[TR3driver]

Bet the radio chassis was negative grounded, without a fuse to that, but the antenae sheild was clamped to the positive grounded bumper.

Bingo! Someone give that man a cigar!

My friend knew about the radio chassis, but didn't consider that the antenna mount would be connected to it. It worked fine at first because the bumper mounts were so rusty that the bumper wasn't grounded to the car! But after bouncing around for several hundred miles, something must've rubbed through the rust and made a good connection.
The in-line fuse didn't help, because it was in the positive lead. The short was through the negative lead.

Even though it wasn't my car, you might say the whole experience left me convinced that negative ground is better

Fortunately, we had a roll of "200 mph" tape, which doubles as electrical tape in a pinch, so we were able to cobble up enough wiring to finish the trip. Even the radio (an old tube model) survived the experience.

 

[tedwone]

On the subject of positive ground cars, I will add an experience my ex-wife had with our 62 MKII Jaguar. One morning she called me and told me that the car wouldn't start and appeared to have a dead battery. I told her to call the auto club. When the driver arrived he told her the battery was installed backwards. She called me again and I told her that the car was a positive ground car and that the battery was not installed backwards. The driver who the auto club sent refused to jump start the car because in his opinion the battery was not installed correctly and he was not going to take the responsibility for damaging the car. When the dust settled I decided to change the car to negative ground and have been doing so with all of my old British cars ever since. Also, not many accessories out there use positive grounds.

 

[TR3TR6]

My TR3A is still positive ground mainly because I had already installed a positive electronic ignition. I have since installed an positive ground alternator. The only thing you have to change in the alternator is the rectifier. There use to be a kit sold on Ebay that did the conversion which was pretty cheap. I have been using the alternator for a number of years with no problems. Have also added an electric fan.

 

[SPACER]

Hi jf,

My 59 TR3 still has pos gnd. & it works fine.
Also has halogen headlamps.
I wired in a lighter outlet for a GPS. It works fine as well.
Also added a led CHMSL. which also works fine.
I see no reason to change the polarity.

Bob

 

[TR3TR6]

I just checked on Ebay to see if the positive conversion kits for alternators were still available, they are; but they have gone way up in price since I purchased mine. I also noticed the kit has more parts in it then the one I got years ago. I would go with the negative ground setup.

 

[Born_Loser]

I just changed the battery on my positive ground TR last night. I could definitely see a big problem - both my wires were blue - painted black by the PO. The new battery has the "+" and "-" so far toward the front edge, the battery mount rail covers them. When I got finished, I realized there is absolutely no way someone would know it was a positive ground just by looking. A future "jump start nightmare". I picked up a red cable and added it. If you leave it positive ground, it just always has to be on your mind. If you go negative, its one less thing to worry with, IMO.

 

[bobhustead]

Hi jf,

My 59 TR3 still has pos gnd. & it works fine.
Also has halogen headlamps.
I wired in a lighter outlet for a GPS. It works fine as well.
Also added a led CHMSL. which also works fine.
I see no reason to change the polarity.

Bob

I assume you wired the lighter neg ground and the receptacle insulated from the car system?

 

[Geo Hahn]

I pondered whether the hot cable on a positive ground car is best to be red or black. IOW - red to indicate 'hot' or black to indicate 'negative'?

In the end I chose black and use a braided ground cable from O'Reilly.

 

[TR3driver]

I pondered whether the hot cable on a positive ground car is best to be red or black. IOW - red to indicate 'hot' or black to indicate 'negative'?

FWIW, I would go with black to indicate negative. Black also indicates hot when working on home AC wiring, so that seems consistent to me.

 

[Geo Hahn]

 

[Born_Loser]

Had a little trouble finding an official source to support my Black is "-" position, but here is one: https://www.answers.com/Q/What_color_wire_is_negative_on_a_car_battery If they can put it on the internet, it cant be a lie.

 

[Geo Hahn]

Ahhh... the polite (and erudite) wisdom of the internet: "your an idiot" -- priceless.

As for "what color is the negative wire for everything. BLACK!!!". I guess he never worked on a German car (brown ground wires) or, for that matter, our positive ground British cars (black + ground wires).

 

[TR3driver]

Here's a slightly more authoritative reference, for black being negative hot in a positive ground DC system:
https://www.arcraftplasma.com/welding/REF.pdf