Blimey, only just fixed the low beam head lamp and already another minor lamp issue.

This time its the Brake Check Light that won't light up with the ignition switch turned to "start". Probably hasn't been working for some time but I had not noticed.

Lamp is not blown and brake differential pressure switch is open cct (all good!).
The brake switch grounds the lamp when something goes wrong with the brake system and bridging the connection here to ground does light up the lamp (so its all good here!).

Unfortunately I don't have a wiring schematic for the GJ, but do have one for the GH.
Probably be the same concept viz,
. there is a relay that gets energised with the ignition switch on "start"
. this relay grounds the lamp whilst starting the engine (functions as a momentary blown lamp check!).

The GH service manual just calls this relay the "lamp relay".

The question is: where is it to be found on the GJ?

The full wiring diagram is now available in a later post


wiring diagram shows 5 relays in the group of relays
3 relays the same # two wires
2 relays the same # three wires
GJ --GL and GSR

Number 73 brake test relay - wire colours BY and BW - B=black Y=Yellow W=White
74 next to 73 is the same relay - called warning lamp relay. B=black - R L R= red - L=Blue
72 brake proportioning switch
75 turn signal
76 hazard

Thank's buffy.


In your service manual - is there a picture of the relays/flashers cluster that identifies the various items?
There are a bunch of these relay's (flasher's) under the dash and it would be a PITA to pull them out one by one until you get the lucky strike.


I need magnifying glasses to read those wiring schematics as well!
They are more like connection diagrams and quite poor on the schematic detail.

Brings back memories, and not good ones.

The Sigmas have a dual circuit brake system, if one loses pressure the light should go on.

Problem is, the master cylinder and integrated proportioning valve gunks up so badly with worn rubber from cups the switch never gets to do its thing, even if one circuit loses pressure due to worn brake cups.

Do yourself a favour, test your brakes on a dirt or wet road, and see if you can get all wheels to lock up evenly.
Chances are you will get wheel lockup on one of the fronts (one front piston hanging up) and the rears doing nothing (proportioning valve not working)

Remove and clean out the master cylinder, rekit if needed. If you have never touched the front brakes, cleaning out the front pistons and bores might be a good idea too.

Visit your test place and test again.

@MadMax,

I replaced the rear disc brake pads a few weeks ago and took it out for some heavy braking.
Car stops smoothly but I've never tried to lock up the wheels, on any car.

Is this the only way you can test the proportioning mechanism?

for you
I can scan the GJ supliments make them a PDF
then email them to you .... just in case I croak
Think about the parts that are missing from your Repair manual

In the repair manual
no real eye visual pictures of the relays as they sit in the vehicle
at the top of the wiring diagram all 5 relays show as a straight line all togeather

.. you whooss ! :slap:
the flasher and hazzards relay will click and are not the ones you seek
That leaves you three all brake related

oh ---the relays fail due to a age or a voltage problem spike or low volts

@ Buffy
Thought's of croaking! Your chemo has gone well I hope?

For the most part, my GH service manual has been pretty applicable to the GJ model.
But your service manual seems to covers both models and highlights where they are different (as in the headlamp assemblies!).
It, for sure, would be fantastic to PDF some select "GJ" specific supplementary descriptions and share it.

Unfortunately my hearing is, lets just say, "impaired" and gives me trouble with directivity of sound sources.
The hazard flasher still clicks and is a metallic round can (I can find that one!).
The indicator flasher I repaired once (with a new capacitor!) and hasn't made any loud mechanical clicks for years (its in that group of black boxes!).

I will pull each black box out until I find the culprit, its just a bit awkward to do hence the question.

The sigma GJ SE has disc brakes on all 4's, and seems to be powered by a twin circuit system.
The mechanics of what triggers the brake failure switch would indeed be interesting (I just called it a "differential pressure" switch).

I think you are right in that the lesser sigma's had rear drums with associated proportioning valves.
Not sure if MadMax's comment applies to this twin circuit all disc system, but I am sure he will tell if it is.

The full wiring diagram is now available in a later post
.
..
oh great there is a separate wiring schematic page for a GJ SE with more relay wires

one on the bottom is 92 brake proportioning switch
up one- 93- brake test switch
up 2- 94 -warning lamp relay
up 3 - 95 - turn signal relay
up 4- 96- hazard


http://i253.photobucket.com/albums/hh59/magnabuff/magna/relays.jpg (http://s253.photobucket.com/user/magnabuff/media/magna/relays.jpg.html)

http://i253.photobucket.com/albums/hh59/magnabuff/magna/sigma%20brakes.jpg (http://s253.photobucket.com/user/magnabuff/media/magna/sigma%20brakes.jpg.html)

Thanks Buffy.

Can't quite yet fully comprehend the whole story of the brake lamp circuit.
Might switch 93 be part of the ignition switch?
Is lamp 90 the brake warning lamp in the instrument panel?
Where does wire BW (middle of switch 93) go to (another relay?).
Certainly seems the GJ circuit is quite different than the GH circuit.

So far it only makes sense if the 2 upper "dots" (say pin 1 & pin 2) of switch 93 is bridged with the ignition in "start".
And pin 1 is bridged with pin 3 with the ignition switch in "on".
If this switch 93 is a relay then pin 4 might energise it according to these ignition switch states.
(its a bit speculative on my part!)

if you save this image to computer (right click save image as )
and use Window Picture and Fax viewer--- you can increase size of page and move it around for clarity

http://i253.photobucket.com/albums/hh59/magnabuff/magna/this%20is%20the%20Se%20page.jpg (http://s253.photobucket.com/user/magnabuff/media/magna/this%20is%20the%20Se%20page.jpg.html)
http://i253.photobucket.com/albums/hh59/magnabuff/magna/Scan.jpg (http://s253.photobucket.com/user/magnabuff/media/magna/Scan.jpg.html)
..
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http://i253.photobucket.com/albums/hh59/magnabuff/magna/legend%20se.jpg (http://s253.photobucket.com/user/magnabuff/media/magna/legend%20se.jpg.html)
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http://i253.photobucket.com/albums/hh59/magnabuff/magna/sigma%20gl%20gsr.jpg (http://s253.photobucket.com/user/magnabuff/media/magna/sigma%20gl%20gsr.jpg.html)

I think you are right in that the lesser sigma's had rear drums with associated proportioning valves.
Not sure if MadMax's comment applies to this twin circuit all disc system, but I am sure he will tell if it is.

Yes, the most problems I had with Sigma brakes was on a GH with rear drums.
Any emergency braking in the dry would lock up one front wheel while the other 3 did nothing, I ended up in the middle of a very wet intersection like that.

Turned out one front brake piston was seized, while the proportioning valve in the master cylinder had long ago stopped working altogether due to accumulated grot.

I have also owned a GJ with 4 wheel discs but never had problems with the brakes, didn't really have it long enough to find out. (Lent to son's girlfriend, they broke up and I never saw the car again. Was tempted to report it as stolen, but Meh! Good excuse to upgrade to a Magna.)

The brake warning light operates simply. Spring between primary and secondary piston, if one loses pressure the spring gets compressed and the little lever on the brake warning light gets pushed over and the light goes on.

Thanks Buffy & MadMax.

Surely that was meant to be a sad excuse to "downgrade" to a magna!!!!!!!

Those scans are very helpful indeed.
I DL'd them directly from Photobucket to get the original higher resolution uploads.
(for info - right click on picture - select "open link in new tab" - DL picture from the site that opens in the new tab.)

Looks like block numbered 93 is indeed a relay (brake test relay) and is energised from the ignition switch (presumably when in the start position).
With 93 energised, it grounds the "brake condition warning" lamp (209) in the instrument panel, whilst the engine is being started.
This "momentary" circuit is effectively in parallel with the "brake proportioning" switch (92) that also grounds lamp (209) when there is some issue with brakes.

Relay (93) also operates the seat belt warning lamp and this happens to also not be working (except when there is frost!). (Maybe the brake check light also comes on during frosty morns?).
All this means that relay (93) is special purpose relay that includes a timed 'latch on' function for the seat belt warning lamp.
Hopefully I can fix it!.

I found the brake check relay.
One of the terminals is intermittent when doing a resistance test (probably explains why sometimes it works and most times it doesn't).
The whole thing weighs only 30 grams and so I doubt that there are electro mechanical relay's in there.
Whatever is in there its glued in, preventing me to take a closer look at the actual contents.
The is a, high one way - low the other way, resistance reading across a pair of terminal suggestive of some active electronic components (diode?).

After trying to prise it open, something else must have failed internally, as the seat belt warning lamp now stays on.
So I've left it out all together.

Made by G.W.E Australia part number 4251431.
Google search comes up with nothing on G.W.E Australia to resembles an electrical company.

If any one spots an old sigma GJ at the wreckers let me know.


The relay cluster is under the dash, on the right side of the steering column (behind the fuse box panel!).


http://i.imgur.com/klnrnj8.jpg

Since the car is no better of with a faulty relay, or without the relay at all, I decided to pull the module apart come what may (nothing to loose!).


Surprisingly, I was able with some force to pull the cap off.
Inside is an dual electronic relay on a small cct board.
I have followed the tracks to sketch out the schematic for these relay circuit's.


Found the faults and repaired the thing.
This after nearly tearing my hair out because the replacement OEM transistors were totally out of specification and just didn't work.


If anyone is interested at all, I can post a picture and the schematic.


Thanks to Buffy's provided schematics (above) I was able to get a handle on how it all hangs together.

if you can't buy the part new

might help someone else

This is the PCB assembly inside the can.


http://i.imgur.com/0UDoHTZ.jpg


This is the schematic diagram of the PCB assembly.

http://i.imgur.com/xZO9GtC.jpg


The red circled areas donate faulty components / dry solder joints.
The replacement BC639 did not work in this circuit.
The BRY56 is a programmable Unijunction transistor (PUT).


Quick explanation:
The PUT is gated on when the voltage across the 33uF capacitor is high enough (time constant determined by the 190 kohm resistor).
With the PUT triggered it grounds the base of the BC639 transistor to turn it off.
So the lamp in series with the transistor is initially turned on and after some time it turns off (seat belt warning lamp).

nice repair

Although the electrolytic capacitors look undamaged in this case, with really old items it is frequently worth replacing them when replacing other components as these do eventually fail when the electrolyte dries out. However if you've already put it back in service I wouldn't pull it out again just to do this.

@ WytWun

Very true.
In fact the 33 uF capacitor only measured 16 uF and explains why the lamp on duration was very short (when it was still working).
I replaced it with a 44 uF capacitor and it stays on long enough to be noticed (about 5 sec).

Not sure why the other capacitor is there, but guessing it provides a low impedance bypass for voltage spikes (prevent false triggering of the PUT?).