11 replies to this topic

[Danny s]

Hi i need help I only find contradictory information on forums.
I have an lh Torana I have fitted a late model SLR cluster with the seperate brake fail light. I have a late model master cylinder with the built in 2 pin pressure switch. One side goes to the earthing terminal on the ignition switch and actually gets earthed in start position. The other side goes to the cluster wiring plug ( tan wire) the warning globes are all connected on the positive side via the looping pink wire which has 12V with ignition on. So it waits for a earthing signal from the ignition switch in start mode to test the globe but how is this possible when the pink feed wires lose 12v on start position and regains 12V when engine has started and you have let go of the key
Gm wire the circuit like this to give maximum voltage under cranking so you get the earth signal under cranking but only 12v in ignition position
Surely it’s not like the old system working off the park brake earth

[ben23]

Because ignition power backfeeds up the resistance wire while cranking as the pink resistance wire and yellow bypass wire both join at the engine harness, and the pink resistance wire joins the ignition on circuit at the ignition switch.

 

The early LX and LH system with the single pin switch works the same way except if the switch is unplugged the light will still illuminate when cranking which doesn't give you any indication that something is wrong. It also means that with the park brake on you don't notice if there's an issue as well, hence why they introduced separate lights.

 

The two pins of the later brake fail switch are actually joined in the switch, and the circuit looped out to the switch and back, that way if the plug is disconnected the brake fail doesn't illuminate at all and you know something is wrong, if the light illuminates during cranking then you know the light works and the circuit is intact. If the switch is activated by a brake fault it earths both pins to the body of the prop valve.

Edited by ben23, 24 November 2025 - 06:27 PM.

[Shiney005]

Any idea when the change was?  I thought the separate light in the dash was an A9X thing.

[yel327]

Any idea when the change was? I thought the separate light in the dash was an A9X thing.

During HJ I think.

[S pack]

Any idea when the change was?  I thought the separate light in the dash was an A9X thing.

ADR 31 on and from 1st January 1977. 
 

[yel327]

ADR 31 on and from 1st January 1977. 
 

 

As per normal GMH bought it in early.

[S pack]

As per normal GMH bought it in early.

The two wire pressure warning switch and the separate brake fail light were introduced during HX and LX production, at the same time as the arse about big nut cast iron master cyl.

My brother had a 1976 HX, it had two lenses in the fascia but only one combined handbrake/brake fail warning lamp and a single wire pressure warning switch.
 

[yel327]

The two wire pressure warning switch and the separate brake fail light were introduced during HX and LX production, at the same time as the arse about big nut cast iron master cyl.

My brother had a 1976 HX, it had two lenses in the fascia but only one combined handbrake/brake fail warning lamp and a single wire pressure warning switch.
 

 

I'm pretty sure the sports dash with the high beam light in the Speedo appeared near the start of HX. ADR31 didn't appear on HX commercials or HZ or WB commercials.

 

I think the speedo odometers went from 5 to 6 digits during HJ and then the blue high beam lamp appeared early in HX ready for ADR31 by 1/77 on passenger cars. 

[Shiney005]

Odometer changed in August 1975 in LH Torana.

[S pack]

I'm pretty sure the sports dash with the high beam light in the Speedo appeared near the start of HX. ADR31 didn't appear on HX commercials or HZ or WB commercials.

 

I think the speedo odometers went from 5 to 6 digits during HJ and then the blue high beam lamp appeared early in HX ready for ADR31 by 1/77 on passenger cars. 

Agree, ADR 31 only applied to passenger vehicles, however, according to GMH certain features of ADR31 would be incorporated into production of commercial vehicles.

According to the HZ parts book the two wire warning switch Pt No. VS13899 is used in all models. 
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Edited by S pack, 30 November 2025 - 02:28 PM.

[S pack]

Any idea when the change was?  I thought the separate light in the dash was an A9X thing.

Hey Laurie, the answer to your question is all LX Torana models got the separate brake fail light and the two wire fail warning switch from 1st January 1977.
 

[Shiney005]

Make sure you leave that GMP&A folder to me in your will Dave.