ALTENATOR

[mandarawessels]

hI ALL

 

i'M INSTALLING AN ALTENATOR IN MY TR4 .

DOES THAT MEAN I WILL HAVE NEGATIVE EARTH AS A RESULT?

I'M ASKING BECAUSE I BOUGHT ELECTRONIC IGNITION BUT IT IS FOR POSITIVE EARTH.

TX

JOHN

[Rhodri]

John, very few alternators were positive earth, and I mean very few, so yours is probably negative earth- I don't know how you would tell? Dynamos can be both positive or negative, you polarise them when you install them.

[Tr4Tony]

Pretty much anything modern is negative earth, so your ignition unit most likely wont work. Moreover youre likely to damage it if you connect to test, so id say take it back quick and buy a negative earth unit.

 

Regards

 

Tony

[mandarawessels]

Pretty much anything modern is negative earth, so your ignition unit most likely wont work. Moreover youre likely to damage it if you connect to test, so id say take it back quick and buy a negative earth unit.

 

Regards

 

Tony

THANKS TONI,

THAT'S WHAT I THOUGHT.

CHEERS, JOHN

[Badfrog]

Hi,

 

True, you need to change the ignition gizmo to a neg-earth unit. To obtain neg-earth, you need to switch the battery cables. Then flip the ammeter wires to respect this new polarity, then only install the alternator. Modern alternators bear their own regulator, so you'll have to remove the original regulator : basically, the two brown-yellows and brown-blue wires must be tied together and you'll also want to tie a large red wire (for a permanent plus) going in an empty socket in a larger fusebox than the original one (the Lucas 8-fuses box is OK). The black wire should be neutralized.

 

You can keep the ammeter in the dashboard for "origin" purpose and install a voltmeter in the engine bay, close to the fuse box. The VM will show 12 volts at rest and 14.8 volts above 1500 rpm.

Edited September 8, 2008 by Badfrog

[ianc]

See Section J4 of the Technicalities CD for a lot of helpful information on changing polarity, installing an alternator, eliminating the regulator box etc.

in addition, there's quite a lot on the Forum about the choice of alternator, but always remember that your original wiring was sized to cope with a maximum of about 25-30 amps, not the 60+ amps that some modern alternators can supply (to cook your wiring!).

Ian Cornish

[mandarawessels]

See Section J4 of the Technicalities CD for a lot of helpful information on changing polarity, installing an alternator, eliminating the regulator box etc.

in addition, there's quite a lot on the Forum about the choice of alternator, but always remember that your original wiring was sized to cope with a maximum of about 25-30 amps, not the 60+ amps that some modern alternators can supply (to cook your wiring!).

Ian Cornish

Ian

I assume that the system won't spontanuously draw more amps unless you put more load(electrical equipment)on it?

cheers,

john

[Badfrog]

See Section J4 of the Technicalities CD for a lot of helpful information on changing polarity, installing an alternator, eliminating the regulator box etc.

in addition, there's quite a lot on the Forum about the choice of alternator, but always remember that your original wiring was sized to cope with a maximum of about 25-30 amps, not the 60+ amps that some modern alternators can supply (to cook your wiring!).

Ian Cornish

 

Ian,

 

You definitely want an increased output to cope with cold and rainy hight driving, so staying low would not be very useful. A very classic move was using TR5 or GM alternators . These give around 45 amps. No problem there. I did the Nippondenso conversion myself and nothing cooked. It's a 45 amps unit :

 

http://www.vicic.com.tw/alternators/vdi10351201.htm

 

Besides the piece weights only 6 lbs. A real improvement. Of course you want to use a small belt conversion and check for the idela pully size to avoid excessive rotational speed. All majors suppliers provide the necessary "paraphernalia". A good site:

 

http://www.minimania.com/web/SCatagory/ELE...28/ArticleV.cfm

 

An of course the Dan Masters papers as published by the VTR:

 

http://www.vtr.org/maintain/

 

Regards.

[ianc]

John - you are correct, the system won't spontaneously draw more amps to power the electrics on a standard car, but many people swap to an alternator because they have electric fan, spotlamps, more powerful headlamp bulbs and even electrically heated windows (yes, they are available!). This lot adds a significant load and many alternators can cope with that and more. I have a 28-amp (TR7-type) alternator, which is adequate for my needs, and I would be prepared to go to about 45 amps if (and only if) the car's wiring is in a good state. The wiring I have seen on some cars is really scary - a bonfire in the making!

Ian Cornish

[mandarawessels]

John - you are correct, the system won't spontaneously draw more amps to power the electrics on a standard car, but many people swap to an alternator because they have electric fan, spotlamps, more powerful headlamp bulbs and even electrically heated windows (yes, they are available!). This lot adds a significant load and many alternators can cope with that and more. I have a 28-amp (TR7-type) alternator, which is adequate for my needs, and I would be prepared to go to about 45 amps if (and only if) the car's wiring is in a good state. The wiring I have seen on some cars is really scary - a bonfire in the making!

Ian Cornish

thanks Ian.

I still have to buy my loom,so that will be new, the only extra I've planned is an electric fan, which arrived today.

cheers, John