TR4/4A TR4a charging issue

[tdskip]

Hi guys - if I don't get more than 12.8v at the battery even at 3k RPM then I seem to have a charging issue. The generator has been rebuilt - but after the carb fiasco I'm not going to make any assumptions.

One odd note - my amp meter is reading backwards so I go negative amps as the RPM climbs. Dash ignition light is on at all times.

Wiring looks to be properly connected but this cars wiring was "improved" and there is a big bundle of wiring that has whho knows what going on in there...

She is positive earth still.

 

[HerronScott]

Tom,

Positive earth? TR4A's were negative earth.

Scott

 

[HerronScott]

Tom,

Check out the TR4A wiring diagram in this PDF.

Advance Autowire TR2-TR4A wiring diagrams

Scott

 

[startech47]

Did you polarize the generator when you put it in?

 

[tdskip]

Tom,

Positive earth? TR4A's were negative earth.

Scott

LOL - that was gnawing at me but I checked Haynes which was the only manual I have out there and I thought it said 4a were positive as well. This was also how it was connected when I bought.

The new but uninstalled Petronix that came with her is also a positive earth unit.

That explains the gauge. :eeek:

What if any other changes are needed before I switch the battery polarity?

Thanks!

 

[HerronScott]

Tom,

Never had to do it but I think the main areas would be ammeter cabling (which is already correct!), coil cabling and repolarize the generator.

If there's an original radio installed, you'll want to make sure it's switched to the correct polarity.

Scott

 

[TR3driver]

Never had to do it but I think the main areas would be ammeter cabling (which is already correct!), coil cabling and repolarize the generator.

Just watch out for any aftermarket electronics (like the Pertronix).

 

[tdskip]

Thanks guys - do you repolarize at generator or control box?

 

[djwoody]

My '67 TR4A is also positive earth.

I plan to convert it over to negative before the winter so that I can connect up my new modern stereo over the winter. From everything I've read it's a pretty straight-forward conversion but I am always nervous when it comes to tinkering with the electrics.

I believe you do repolarize at the generator.

 

[TR3driver]

I believe you do repolarize at the generator.

Either way will work. Personally I do it at the control box, just a very temporary jumper between F and A will do (although you'll get lots of sparks). For fewer sparks, disconnect the wire from F and brush it against A.

But it's still the generator you are polarizing (actually magnetizing with the proper polarity).

 

[HerronScott]

LOL - that was gnawing at me but I checked Haynes which was the only manual I have out there and I thought it said 4a were positive as well. This was also how it was connected when I bought.

Sounds like many people have followed their Haynes manual.

Scott

 

[TR3driver]

It's not just the Haynes; my 4/4A Bentley has only one diagram and fails to mention that it's only for a TR4.

 

[tdskip]

Ah ha - so I'm not a (complete) idiot then. (Rich C - too easy so be quiet)

Still should of caught it, but this makes me feel slightly better.

Thanks guys.

 

[HerronScott]

It's not just the Haynes; my 4/4A Bentley has only one diagram and fails to mention that it's only for a TR4.

Randall,

Interesting I didn't recall that being wrong but then again it's been 25 years.

The Autobook TR4/4A workshop manual (mostly rehash of factory) is also wrong so the only correct one that I see is listed in the TR4A owner's manual (and what's posted on the Advance Autowire site).

Scott

 

[cheseroo]

Ah ha - so I'm not a (complete) idiot then. (Rich C - too easy so be quiet)

I'll have you know that the amp gauge appears to work correctly in the newly resurrected TR4a. The number and quantity of fuel leaks is another matter. I shall soon be in a position to challenge you to a match race between loooong dead TR4a's. BTW, how long has it been since Pirelli made bias-ply tires?

Also if anyone in the OC/LA area would like a 69 TR6 shell with rotted sills and severely rotted rear frame, let me know. Sometime in the next week it will be going to the crusher but if someone wants it I would rather see it going to good use.

 

[tdskip]

I'll have you know that the amp gauge appears to work correctly in the newly resurrected TR4a. The number and quantity of fuel leaks is another matter. I shall soon be in a position to challenge you to a match race between loooong dead TR4a's. BTW, how long has it been since Pirelli made bias-ply tires?

You are on!

Now what would be really cool is for you to bring it on the SoCal TT.