Clutch switch - and then not ?

Dear all,
had some trouble with an ECU which roasted. Got another one for replacement (and re-mapped), and since I had the following problem. Th revs does not go down when depressing the clutch, so the switch seems to be in fault. However replacing it has not helped. There is aloo no difference if I short the circuit or not. I tested the cables running from the ecu to the switch, and the loop is all good.

So, back to the ecu. Can the clutch switch function be disabled in the mapping ... or what should I look for?

As always, humble for the level of help I always get in here.

Thx, Lars

Bump

Hi, was by any chance the replacement ECU automatic ? Cos then it needs an internal mod for the missing clutch switch circuit. I dont think it's possible to map out te clutch switch.

Buckhandle said:

I tested the cables running from the ecu to the switch, and the loop is all good.

Click to expand...

which "cables" from ECU to switch ? cos it's only one wire to pin 35 black plug, check if you have earth on the black/green wire in the switch's plug, it's description in the WSM is wrong as it closes to earth when the clutch is depressed

Bummer - I belive it might be an auto-unit ...

Any clue on the details of the mod needed?

It's not a very simple mod, two resistors must be inserted in the PCB and the circuit completed but i didnt do it myself. Better sell that ECU and get a proper one

eventually if you are skilled enough with electronics open the original ECU, follow the circuit with magnifier and compare with the auto ECU then you'll see where the resistors are missing and transplant them

As we are on the TD5 forum l will assume this is a TD5 we are talking about.

Check that you have the correct switch fitted.

The clutch switch on the master cylinder can NOT be replaced with the later TDCi Puma one.
The switches look exactly the same, in fact the pedal box and master cylinder look identical, but the Puma clutch switch works the opposite way electrically (to a TD5 one) and will tell the ECU in your TD5 that the clutch pedal is down when it is actually up, and vice versa.

This would result in the issues that you describe with engine revs not dropping, well it did on mine anyway.

I found this out after fitting a new "take off" clutch pedal box/master cylinder assembly from a Puma into my TD5.

After a bit of head scratching l tested the switches and found that they sent opposite signals (normally open and normally closed contacts) and l had to fit the switch from my old master cylinder.

Embarrassing ... I just realize I have replaced my NNN500020 with a NNN500030 ECU .... (Note to myself, reading glasses - upper left chest pocket)