Hi

 

Does anyone know where I can get the diagram to make this swtich?  or perhaps buy a ready made one? It relates to Octavia's which start cold but don't start or unreliably start hot.  I found this on the moneysavingexprt forum but no details about the switch.

 

Thanks

"The problem appears to be quite common and can be caused by the engine "mapping" which does not allow fuel through to the engine when hot unless the starter motor is turning the engine over at over 250 rpm.

As the battery and starter begin to wear...the starting speed reduces and hence you get difficulties starting (only when hot though?!!!?).

Several forums have detailed wiring in a switch to turn off the temperature sender temporarily, when starting from hot... which basically fools the car into thinking it's engine is cold and hey presto it starts first time."

Surely it would be loads easier getting a new temp sender?

The old ones quite often fails which requires a new one. Aftermarket ones are no good and don't last long.

Surely it would be loads easier getting a new temp sender?

The old ones quite often fails which requires a new one. Aftermarket ones are no good and don't last long

Yes and no.  If my problem is a faulty sensor then great but if the issue is with the mapping then a new sensor isn't going to fix it.  The problem is that the car starts when cold and is intermittent when try to start hot, most times it won't start.

Fit a genuine VAG revised green CTS & that should solve the problem.

I dont think what your after exists tbh. A new sensor is only £30

That mse thing is a bit misleading the temp sensor has no bearing on engine rpm when hot that would be down to starter or crank sensor issues. The cts is a known weak spot and worth replacing with the newer type as it cures a lot of issues. Wiring in a switch would be more hassle and prob more expensive than just fitting a new one. If you've got hot start probs I'd be more inclined to think it would be crank sensor or starter motor.

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In addition, a weak battery will cause this, although typically this fault is reported more over the winter months.

I would of expected a weak battery or starter motor would be causing cold start problems not hot.

I would of expected a weak battery or starter motor would be causing cold start problems not hot.

When it is cold there is no rpm check on the cranking speed. When the engine is hot, fuel is only supplied when a minimum rpm is reached (time related). Pulling the connector on the temp sensor makes the ECU 'think' the engine is cold. The problem is that is also turns the glow-plugs on, which can make things worse.

The most like cause of this problem is a dying battery. When the engine is hot, try jump stating it. If it starts easily, the cause is the battery.

If it's not the battery, check the condition of the earth strap and cable that feeds the starter.

If it's none of the above, you need to service/replace the starter motor.

thanks for the replies guys, will get the auto sparky to look into it.