Car not cranking (intermittend): clutch switch?

[vtraudt]

Over the last couple of days, the car sometimes did not crank (2002 Allroad manual).
Pressing the clutch pedal several time, moving shifter, pressing brake pedal, key in/out ultimately allowed the car to crank (not sure which did the trick).

Getting under the dash today, I found
a) 2 white switches (look the same; one for brake, one for clutch)
b) 1 mirco swtich on clutch pedal

a) switch seems to be 'screwed in' via thread in plastic housing. Switch is pressed in when pedal is NOT pressed. Removed switch and checked open/close contact, which it does. What is the function of this switch? How can I properly 'set' the clutch one?

b) removed micro switch physically, but did NOT find where the cable goes to locate the connector to remove from car. Can someone point out where to disconnect the switch.
I am sure there are 2 wires going to the switch? (Could be one wire if switch is grounded and need to connect to ground when pressed; can't tell with sleeve over the wire).

Microswitch is pressed in when clutch pedal is pressed. There seems to be an Allen screw to adjust the position? Pressing the mircoswitch in by hand allowed the car to crank.

c) The microswitch 'crank protection' is likely closing circuit (to ground?). How can it be bypassed (shorten the 2 wires?)


To fix my (currently intermittent) 'no crank', should I
- replace the microswitch
- adjust microswitch with this Allen screw?
- shorten the wires at the switch?

[Chopstixs]

Replace the clutch switch....then send me beer money

[vtraudt]

Can someone help me with identifying the small micro switch (not the larger 2 white ones; still don't know what the white one is for on the clutch pedal).
I took the switch out, checked it. Seem to work fine. Set the 'switch point' a bit earlier (so i don't have to press the pedal down to the firewall).
Worked without problems for 4 days.
Today, couldn't get it to crank AT ALL. Had to push start the car.


Aside from the ordering information for the micro clutch switch (part number? How is it called? Sources?), does someone know if the switch is 'normally open' (NOT connecting the 2 wires" or 'normally closed' (connection between the 2 wires).

In other words: does pressing the pedal 'open' the circuit or 'closes' the circuit.

If it 'opens' when pressed: Can I just cut the wire to 'open' the circuit (all the time).
If it 'closes' when pressed: can I just cut and twirl the 2 wires together to close the circuit all the time?

[walky_talky20]

I'd be happy to help.

First, to discuss the various switches. The one at the bottom of the clutch pedal travel is just for starter safety - so you don't run somebody over if you forget it's a Manual Trans when you hit the starter. The switch at the top of the clutch pedal travel is mainly for cruise control (so it cancels immediately if you forget and hit the clutch pedal with the cruise SET). That top switch also serves some minor emissions purposes. Basically, in certain situations the Drive-By-Wire throttle plate will respond differently depending on whether you are "clutching" or not. It is programmed for the throttle to "hang" or "slow close" upon abrupt throttle lift (to reduce tailpipe emissions), but it cancels this behavior if you touch the clutch pedal (so the revs don't hang while you are shifting). Pretty neat. ANYWAY...

The starter circuit is very simple on your Allroad. It consists of just a few things:
- START signal from ignition switch
- Ground signal from Clutch switch
- ^^Those 2 combined which closes the Starter Interlock Relay
- Output of said relay puts 12 volts to the starter solenoid
- Starter solenoid engages the starter gear and closes massive internal starter motor switch

So the clutch switch is indeed NORMALLY OPEN. When you push the clutch in, it CLOSES. This provides a ground to the starter relay coil.

The ignition switch provides just one START signal. That provides the 12V+ to the starter relay coil. It also provides the 12V+ for the relay contacts (the load).

So there are a couple things you can do to start ruling out problems:
A - Jump the clutch switch (use a wire in place of the switch to permanently close that circuit)
B - Remove and Jump the starter relay contacts (connect the START signal directly to the starter solenoid)
C - Use a multi meter to see if any of the signals or connections are "marginal". Check power and ground to relay. Check resistance across relay contacts when closed. Check engine ground to starter solenoid. Check resistance of relay-to-solenoid wire. Basically check everything. Bonus points if you can check it while it is actually failing.

Obviously A or B will be easier than C. Option A is the least invasive. It will only rule out the clutch switch because it is leaving the relay and all the wiring "in play". That would probably be the most scientific first step. Option B will bypass the clutch switch, clutch switch wiring, and the relay itself. So if you jump right to option B, you won't really know which of those it is, but it is more likely to make the car instantly reliable in the short term - simply because you are bypassing more crap.

We are starting with the easy stuff here. If option B is completed, but problems continue - the failure could be a flaky ignition switch contact, a flaky starter solenoid, a corroded wire at the solenoid or too much resistance at any point in the circuit. If the solenoid doesn't get enough voltage, it won't move with enough gusto to engage the high power internal switch for the starter motor. In that case you may get a "click" but no "crank". Low Battery voltage in general will also create that behavior (I'm assuming your battery was fine, though).

NOTE: Any of these bypasses is deleting a safety feature of the car. It would be unsafe to let anyone borrow the car during the time these safeties are disabled. Bad things could happen.

FWIW, I 5-speed swapped my B5. I opted not to even install this bottom clutch switch and associated wiring. So my Starter Relay is permanently bypassed with a jumper wire. I just remember to start the car in Neutral or with the clutch pedal depressed every time. I also don't let many other people drive my car. If that was a requirement I would have hooked it up properly.

[vtraudt]

walkytalky: Now that's what I call a helpful and complete answer; wow! Thank you very much.
I start with just jumping the microswitch, just to get the car operable (hopefully). Constantly pushstarting is not really an option as you can imagine.
Where is the starter relay located (if I wanted to do "B").
I don't have a problem at all to eliminate this safety feature (heck, this is the first car i drive (33 years driving sticks) that has it); if not permanently, at least until I have time to replace/fix whatever part is causing the problem right now.

So tomorrow morning: znip snip of the 2 microswitch wires and twirl twirl. See if it works.

[walky_talky20]

I'd rather see you use a jumper wire so you don't modify the factory wiring. For example, if you cut the wires now and then ultimately find it was a flaky relay that is causing the problem, now you have a hacked up factory harness that you have patch up. It is just 2 little wires, but in my experience once you cut up a factory harness/connector the reliability always goes down. Seeing as the goal here is to achieve perfect reliability in this circuit, I would rather not see you cut the harness unless completely necessary.

Ideally, I would recommend you harvest some factory small blade-type pins with pigtail wires, like so:



Then use them to jump the desired connector pins (and obviously tape it up so the pins don't touch), like so:



That's just how I would do it. Good Luck.

[vtraudt]

Problem is: I did not find a connector to put a splice in. Wires come out of the switch, and then disappear 'up there'. Hence cutting (yes, not ideal).
Where is connector to the switch?
Or jump on the relay you mention?

[walky_talky20]

I'm almost positive the clutch-start-switch connector is the black connector directly above the white clutch-cruise-switch on the pedal bracket. You should be able to see the black wire jacket snake back toward the clutch-start-switch if you look closely. We can verify wire colors if you want, but I'm pretty sure that's it.

I can get you that relay location later tonight.

Interesting side note: It appears your clutch pedal is constructed of aluminum. The one in my B5 is black. Either plastic or steel, I can't recall.

[vtraudt]

I should get the car back later today (son took it since I had to change the power steering pump on his A4 1.8T; push starting since 3 days exclusively) and will take the kickpanel off and climb under there and check.
Be back then.
Thanks for your help.
Have found 2 sources for the switch:

PartsGeek:
http://www.partsgeek.com/catalog/200...ch_switch.html (ca. $24 plus S&H)

GermanAutoParts:
http://www.germanautoparts.com/partsearch/3b1911807a (ca. $75.53 plus S&H - must be the machined from billet gold).

Will try jumping first (again, none of my cars had it, so no issue).

[julex]

There are two switches on the clutch. One for bottom position for cranking and one for partially depressed position for ECU which is then used as a variable for some ECU functions like idle torque reserve etc.

[8520]

Apparently the car won't run right if you bypass the primary clutch switch.

The secondary one, aka the one for starting is fine to bypass. I jumpered mine a long time ago and have never looked back