7 replies to this topic

[Lima31]

Ok so about 8 months ago i replaced the original style 55A bosch branded alternator with one of the Tuff replacement units. I added another 2ga ground wire from the alternator to the engine and then from engine to chassis with ring terminals.

Then last month during the first drive in about 7 months, I was again stranded with a flat battery. i got a jumpstart and made it home. At home I checked the voltage with the engine running, and it was about 12 volts which suggested another dead alternator.

Replaced the Tuff alternator with a genuine Bosch 120A BXH1250A alternator, as per pic below. Still no charge, low 12V!

Didn't change the wiring. the photo shows the underside. A 4ga wire runs straight from the starter solenoid (which is common to a 00 ga wire going direct to battery positive) through a 60A maxifuse then to the fat B+ terminal. The 2 pins at the top are untouched. The 2ga ground wire runs from one of the threaded mounting bolts to the chassis, and the stock bracket also grounds the alternator to the engine. No difference if the D+ exciter post is connected or not.

Anything else to check before trying a third alternator?

[ls2lxhatch]

Usually the D+ is connected to the alternator fail globe and then to +v at the ignition switch. Most alternators will not work without D+ connected.

[Lima31]

Thanks, have booked in an auto electrician anyway, pretty sure the car is cursed at this point

[Rockoz]

A lot of alternators will eventually start charging whether the D+ is connected or not.

A quick way to check if the alternator is okay is to hotwire the D+.

If the battery is down, you will hear the alternator start to whistle as it throws a heap of power out.

You may or may not notice a drop in revs as well.

You can also use a multimeter to check the voltage if you put the wire to D+ on and off.

The voltage should jump accordingly.

Dont leave D+ hotwired for too long though.

 

 

Cheers

 

Rob

[axistr]

Do you have a working alt light on the dash with ignition on engine not running ? 

[gtrboyy]

Guessing that is vt v8 120a?

 

Should be 2 wire plug at reguator...one for charge light other load sensing wire to positive of battery or like most do loop it to alternator stud.

 

Other thing vaguely remember being 2 types of alternators being sold factory vt item 14v 60/120a & 14v 14/120a iirc

 

Later ones need steep pulley ratio & generally sold on ebay as being same item as first.

[Lima31]

Ok i fixed it, thanks for the help guys. the internet didn't help so will lay it out here.

The BXH1250A / BXH1253 Bosch alternators have five connections to make to work.

GND / casing => 2 awg black wire to block and chassis
B+ terminal => 2 awg red wire to fat starter terminal via a 60A fuse, which is then direct to battery
D+ terminal => brown wire (10220 painless kit #914 is a white wire) which supplies 12V to the alternator via the dash battery indicator light
L terminal => this is a warning light, i wired it back to D+
S terminal => sensor terminal, I connected it to the B+ terminal.

The L and S plug is for an RE60 regulator, for now I cut down some spade terminals to fit.

Would not work unless all of these were connected, and even then the secret trick is that i also had to rev the motor hard for a couple of seconds for it to energise the coils and start charging for the first time.

[Com_VC]

From memory I never bothered with the D+ terminal, don't think this is required if you use the L terminal. ?

 

Also I never fused the B+ terminal, do Holden fuse them?

 

For the L and S plug you can just use a bosch fuel injector type connector.  https://www.ebay.com...&frcectupt=true