Clutch pedal switch - in engine conversions

Hi,

Is the clutch pedal switch required when carrying out engine conversions, 20vt/TDI etc into the older car's?

Is it just used for cruise control?

Thanks

 

Also what about the brake pedal switch?

 

I've run both in the mk2 20v. Not a lot of effort to fit, had to trim the fusebox earth claw for the brake switch & make a hole & trim the gap on the clutch switch to fit. After looking at the wiring diagrams IIRC I can't remember seeing that the clutch switch was only fitted to vehicles with cruise control so figured the ECU would require to see it.

Pretty sure jimmy20v just ran a standard mk2 brake light switch without the clutch switch or mk4/audi/seat brake light switch without any problems though might be worth confirming it with him first.

 

Thanks for the reply.

I looked through the 20vt wiring thread, and it looks like jimmy20v wired in both switches. I guess the brake switch is what kills the throttle when left foot braking on newer VAGs.

I also found this

Which make's sense, I'll leave the wire's in and see if I can get away with not using them

 

I connected to the standard brake switch and put in a clutch switch.
No idea if its needed but i had the pedal box out so did it at the same time.

 

Thanks, It make's sense to get it all as it should be.
According to the diagrams I've got the brake switch is normally open, but the clutch switch is normall closed.

 

Thanks rubjonny. I've set you a pm on a simular subject.

Cheers

 

i found it P39 on the big ecu plug (i didnt make the loom ANdyout did ) , it has the red/white there but no power goes or comes out the ECU pin .. ?

one thing i will say is when its warm the revs go up about 200rpm or hang while changing gear ive read loads and alot of people talk about this same issue ,


some saying its a "trate" of 20v's to protect the turbo?! / to faulty clutch switch / its hit and miss for decent answear ,

all i did see on the measuring block section " 066 " using vagcom it reads 00000111 weather this is as you said in the pushed or open poistion i dont know , without someone else plugging in an getting a reading,

 

The digits should change when the brake & clutch are pressed. If they dont then its not working.

The last 3 bits in field 2 should work like this;

----1xx - Clutch depressed (always 1 in automatic transmission)
----x1x - Brake depressed (brake pedal switch)
----xx1 - Brake depressed (brake light switch)

 

----1xx - Clutch depressed (always 1 in automatic transmission)



Seeing as i dont have the loom / wired to the switch i just have the red/white coming out the correct pin on the ECU ,


From your figures and my reading last night on vagcom , it is tellin my ECU the clutch is always depressed !?

 

Yes, If its always 1 the ECU thinks your clutch is depressed. As above no one really know what it does so its up to you to wire it in if you want it.

I was going to have mine mapped a month ago but they guy said i needed to have all 3 of these working to be able to map it correctly. Something about the ECU holding back as it thinks the brakes or clutch has been pressed.
I have all 3 of mine working now, And i must say i think the torque has improved at the top end.

 

You need the clutch switch as your car will not run as it shuld without it

I found this out on Curby sprint day. Each gear change resulted in car holding on to revs or increasing them during gear change which was not very nice at all.

Only discovered dislocated switch once i was back home. Clicked it in and and Car run 10 times better

Car in qstn is an yr 2000 A3 1.8T

 

i tried to wire it in but i dont have the correct power from the ECU , it says pin 39 red/white 12v on auto data , and i have 0 in or out of that wire , ive checked it on the ECU pin itselfs theres nothing ,

 

This is for a BDE V6 4motion but same loom really.



You need a 4 pin brake light switch to make it easy.
Pin 1, +, E/04 (Brake lights), & Pin2/cluth swith +
Pin 2, To clutch switch
Pin 3, T10e/5 (T121/55)
Pin 4, T10e/4 (T121/56) & E/03 (Brake lights)

The Pin 39 (Clutch) & 56 (Brake) are both sensor wires. They dont supply 12v, You have to supply 12v to them for the ECU to read the signal.

 

ok brilliant thanks for this , i assumed that 12v on auto data my mistake ,


how do you go about mounting the new ages clutch and brake switch , i know they have that fancy quater turn locking tab/ears which then makes the switch lock into its position ?

1C0 945 511A RDW - brake swtich on the "BDE " Mat- mk3 talked about

6Q0 945 511 - 4 pin brake switch "was a 1J0 927 189F "

6Q0 927 189 - clutch switch



thanks

 

Yeah the new green MK4 4 pin brake switch is just an "insert and twist" job. You have the plunger resting against the brake pedal as you twist and that sets its length.
I had to file a small bit out for the clutch but it was not much, Both work great.

 

clutch switch:
1 - to ecu
2 - ign live feed

brake switch:
1 - permanent live (use plug e pin 4)
2 - ignition live (use same source as clutch switch)
3 - to ecu
4 - to ecu and brake lights (use plug e pin 3)

I'm currently wiring this up on my loom but i'm reading my diagram wrong I think. Can I confirm the clutch switch wiring is the wrong way around? Should it not be Clutch 1 linked into Brake 2 with an ign live?