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NEG or POS ground?

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NEG or POS ground?
#1
  This topic is about my 1954 Austin-Healey 100
UALcaptain Avatar
UALcaptain Mark Cuppernull
Winchester, VA, USA   USA
1954 Austin-Healey 100 "Tilly"
My second question of the day, and I apologize in advance for my naivete ... My BN1 has a single 12 volt battery in place of the dual six-volts. It appears to me that the positive terminal leads to the battery cutoff switch, and thence forward thru the driveshaft tunnel and up the firewall to fuses, ignition switch, etc. This wire is cloth covered. The negative terminal is connected to a very heavy gauge wire (rubber of plastic covered) that leads thru the driveshaft tunnel and then on to the starter relay / starter motor (forgive me - I'm describing from memory). I was told the car was "converted" to negative-ground. Before I attempt to charge the battery, I'd really like to verify negative or positive ground. If not apparent already, I am somewhat electrically challenged! Thanks for the help!

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PeterC Avatar
PeterC Platinum Member Peter Caldwell
Madison Wisconsin, USA   USA
If you need to charge the battery, connect the charger cables correctly. Pos to Pos and Neg to Neg. the car's polarity is not a factor.

Peter C


Member Services:
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gramos Avatar
gramos Graham Foster
Kefalonia, Greece   GRC
Peter is quite right , disconnect the battery to charge it .

So ,you say :

negative terminal is connected to a very heavy gauge wire (rubber of plastic covered) that leads thru the driveshaft tunnel and then on to the starter relay / starter motor

this indicates that your car has a positive earth as per original ,
there should be a battery lead going from the battery positive terminal post to the chassis , near the battery .

PAN Avatar
PAN Alwyn Keepence
Ipswich, Queensland, Australia   AUS
G'day Mark,
I'm a little confused. You say that the cable from the positive battery post goes to the battery master switch. So far so good for positive earth (ground). But then you say "thence forward to the fuse". The heavy cable should then go from a separate terminal on the master switch to the chassis to provide the ground. Is that the case on your car? If so then as Graham says, your car remains Positive Earth. A light cable (white with black tracer) goes from a small terminal on the battery switch into the wiring harness and to the ignition coil, to prevent the car from being "hot wired" and stolen.
The battery cable and the wiring harness were not originally routed through the prop shaft tunnel, but along the sides of the chassis rails under the car.
Cheers,
Alwyn

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UALcaptain Avatar
UALcaptain Mark Cuppernull
Winchester, VA, USA   USA
1954 Austin-Healey 100 "Tilly"
Thank you all for your replies. It must be positive ground, as the battery's positive post is connected to the cut-off switch and grounding strap. My questions now are these ... A) I would like to assist the battery with a solid state jumper unit while starting (at least for now). cool smiley I would like to wire in a smart charger quick-disconnect plug. Both of these ideas are defeated by disconnecting the battery first, as recommended above. Would it be safe to charge/jump the battery while leaving it connected? C) Would you recommend replacing the generator and voltage regulator with an alternator? I've noticed this on some big Healey's. My intention is to add reliability - especially on longer road trips (same thought regarding replacing points with an electronic ignition, but that's another subject). Again, thank you for your wisdom!



Edited 1 time(s). Last edit at 2019-01-30 06:33 PM by UALcaptain.

gramos Avatar
gramos Graham Foster
Kefalonia, Greece   GRC
A lot of owners , including me , now use one of these :
AUSTIN HEALEY 100/4 100/6 & 3000 BRAND NEW POWERLITE HIGH TORQUE STARTER MOTOR
Brand new
2 product ratings

£197.95
+ £15.19 postage
Ebay

these make a big difference to the traditional slow start of the 100 ,the engine spins over like a sewing machine !
then do an alternator conversion to get a lot more power in thre wholesystem , charging , lights , etc :






Dynamator Alternator Dynamo Conversion LUCAS C45 Fits AUSTIN HEALEY 3000 62-64
HIGH POWER ALTERNATOR IN DYNAMO CASE DIRECT REPLACEMENT
Brand new

£159.95
+ £35.00 postage

This has the benefit of looking like an original dynamo while giving the output of an alternator .

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