Omega Owners Forum
Omega Help Area => Omega Electrical and Audio Help => Topic started by: Valentin on 01 April 2025, 16:23:12
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Hi everyone,
I just bought a 3.0 MV6 Omega and it's supposed to have the "Controle Technique" kind of the same thing as the MOT ;)
But on the road back to home, I discovered that the brake lights weren't working at all, both of them. I was with a friend following me. AND, if I set the cruise control then it doesn't disengage when I brake, leading to dangerous situation where your first reflex is to push harder the brake, and the car drops gears to accelerate :o until you understand you have to use the cruise control 0 switch or go in Neutral.
After a lot of research on this forum and on other Vauxhall channels, I didn't find this particular case. I did find a lot of people with both brake lights issues on Omega, but never with the cruise control affected by the issue. Some says it's the bulb holder, others say it's the brake switch... Yesterday I tested the brake switch, it has continuity. I tested the supply wire from the fuse F2 to the bulb holder, there is continuity. Same for the ground. Taillight (from the headlight button) they work fine.
And this morning, I tried to clean the bulb holders, guess what, brakes lights work! But... not every time :D and even weirder, either they work or not, it's always both at the same time.
I guess the pedal switch is faulty, and I probably disturbed him yesterday that's why he seems to wake up ??? If I brake and it works, if I stay pushed on the pedal, there is no blinking or odd behavior from the bulb. It's always either full lite up or nothing at all.
I will keep on searching and this evening will try a small road test :y
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It will be switch
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Yep, great chances that's the switch.
I went for a small ride. First I start the car, then brake, the CHECK light on the TID doesn't disappear. I slightly brake several times like 10 / 15 times and at some point the CHECK light turns off. Then I go on a straight line and put the cruise control. Same story, I have to slightly brake 15 / 20 / sometimes 30 times to get the switch to work.
But now, can someone tell me if the 96 Omega has 2 or 4 poles? Because I see everywhere that if you have cruise control you must have 4 poles. On the car it's a 2 poles, on the Heynes Service manual, electrical diagrams, circuit 462, it's a 2 poles that drivez lights and cruise control on the same black/yellow wire (4 poles for the turbo diesel). And seeing the cover and 1/4 clips under the steering column, it's never been opened ;) Everything looks new and untouched over there :y
All the brake switches I find on internet are 4 poles, I don't see any issue to put a 4 poles as there will be 2 who won't be wired, if they are all Normally Open. The one I have has left/right terminals, no top and bottom.
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If it has cruise, it will be the 4 pin switch :y
2 pin is for non-cruise on petrol Omegas.
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As said before, the one which is currently on the car and that seems untoucher from factory is a 2 pin, with 2 wires connector (Black and Black/Yellow)
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If the switch isn't fully seated when fitted it won't work properly. Also you run the risk of damaging the switch and it will require replacement on fairly short order.
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Thanks for the advice :y
The switch is from factory, it seats with no play, no tolerances. When the pedal is pressed, the actuator moves as it should.
Has someone already opened a faulty switch too see why they all brake down at some point ?
Maybe I will do if he's actually guilty :y
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On all the Omegas I had, and all the time I had them, never had brake switch failure. I don't think they are a weak point. We used to replace them when retrofitting cruise control (as cruise needs the 4 pin setup).
if your switch is not working reliably, it's either not seated right, or it's got worn/damaged contacts.
Lastly, all UK petrol Omegas were prewired for 4 pin brake switches, even if they didn't all have the 4 pin switch fitted. I see no reason why EU spec ones would be different.
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Sounds like someone has retro fitted cruise control and not replaced the switch with the correct one.
You need to replace your 2 pin switch with the correct 4 pin one for cruise control.
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On all the Omegas I had, and all the time I had them, never had brake switch failure. I don't think they are a weak point. We used to replace them when retrofitting cruise control (as cruise needs the 4 pin setup).
if your switch is not working reliably, it's either not seated right, or it's got worn/damaged contacts.
Lastly, all UK petrol Omegas were prewired for 4 pin brake switches, even if they didn't all have the 4 pin switch fitted. I see no reason why EU spec ones would be different.
The brake switch harness is part of the dash harness. These are prewired for everything except for Bose/Nav.
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Sorry guys but, I sum up quicky what I'v said before :
- The EU MV6 has cruise control from factory
- The dash harness currently on the car is a 2 wires for the brake switch
- The brake switch on the car has only 2 pins
- On the electrical diagram from Haynes, circuit 462, there are only 2 wires (the 4 wires are only for turbo diesel as it's written TD near the S8 switch)
- If I insist on braking several times, like 30 or 40 times in a raw, at some point the brake lights switch ON on the back and the cruise control disengage, which means they are on the same circuit
I leave for work travel now but next week I will post some pictures :y
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That you have to press the pedal 30-40 times for the switch to work clearly tells you the switch is the fault.
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- The dash harness currently on the car is a 2 wires for the brake switch
- The brake switch on the car has only 2 pins
Is it a manual or auto?
- On the electrical diagram from Haynes, circuit 462, there are only 2 wires (the 4 wires are only for turbo diesel as it's written TD near the S8 switch)
Be aware that CC on those diagrams can also mean Check Control, as well as Cruise Control ;)
If your brake lights aren't coming on then obviously that precludes your safely being able to use the car at all.
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https://youtube.com/playlist?list=PL6PJLmRWCKyAA6H1-QkHBPg7uooUcVPow&si=IDuChxr-y8jxIVUk
Brake light and cruise circuit diagrams for mid facelift.
The 2.5 diesel uses different pins on the switch plug but on both petrol and diesel the switch plug is a 4 pin plug although only 2 pins are populated.
CC is check control for bulb checking purposes.
CRC is Cruise Control.
WEG is the signal from the ABS ECU.
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- The dash harness currently on the car is a 2 wires for the brake switch
- The brake switch on the car has only 2 pins
Is it a manual or auto?
- On the electrical diagram from Haynes, circuit 462, there are only 2 wires (the 4 wires are only for turbo diesel as it's written TD near the S8 switch)
Be aware that CC on those diagrams can also mean Check Control, as well as Cruise Control ;)
If your brake lights aren't coming on then obviously that precludes your safely being able to use the car at all.
Absolutely.
The car is an automatic.
I was aware about CRC and CC on the diagrams. Also, I can confirm another point : the "check" light is ON until we press the brake pedal. Here, it's always ON, until 30 or 40 times I press the brake, when I manage to disengage the CRC, then the "check" light turns OFF. The brake switch is giving the info to both CRC and CC then to the rear lights = that means it's the switch.
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The CHECK light you are seeing - which should show until first brake press - proves the main brake light switch isn't working. Now this is most likely to be the switch itself, but could be damaged wiring obviously.
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Hello everyone !
Finally received the new switch, needed to be 2 persons to remove the old one without destroying it > press the brake the most you can, slide the red cylinder out to the maximum, disengage the 2 side hooks and it's free.
The new switch works perfectly, the brake lights and CRC finally react as they should.
I tried to understand why the old one was faulty, and I think it's pretty simple. When new, the switch rod (grey) is fully extracted. When the pedal pushes the rod the first time on uplift position, it slides in and set the uplift position by default. Inside there are several "clic" positions and each of them is a starting point for the internal actuator to switch on and off. I guess it's to be compatible with several pedal positions on the different cars it's fitted. On the old one, this starting point was broken inside, but there is no way to see it from outside. Thus, the pedal needed to be pressed very hard for the switch to eventually work on another starting point.
Here is a picture of the original part
(https://i.postimg.cc/w73XYxPZ/IMG-20250422-093308.jpg) (https://postimg.cc/w73XYxPZ)
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Glad its resolved, and thanks for posting your findings on the old one :y