Posted: Fri May 08, 2009 6:52pm

My 25 year old Kubota engine is fitted with an AC oil pressure switch which leaks oil and I suspect that the diaphragm has failed. Local car accesory dealers cannot find a match without knowing which make of car might have used a similar switch. Do you know of anyone who might have a cross-reference for AC components to current manufacturers?

Posted: Fri May 08, 2009 7:03pm

As it is only a switch it just requires the thread on the old and new part holding side by side to ensure they are the same. Try an Auto factor - not car accessory shop - but you are far more likely to get help from a Kubota agricultural dealer. If the thread is the same any make will do. Tony Brooks

Posted: Mon May 11, 2009 8:15pm

Thanks, my local garage has loaned me his "box of bits" for me to try some switches. Thread is not the problem so much as the proximity of the starter motor requiring a quite slim switch, or several "extensions". Is not the calibration of the switch to match the engine recommended psi (14.2) a matter of concern?

Posted: Tue May 12, 2009 8:49am

Dear Doug, A hot engine at idle will probably have an oil pressure of perhaps 15 to 25 psi so the calibration of the switch is not that important - especially when you consider its a mass produced item which is likely to have a large tolerance on its settings. Most engines in good condition and the correct oil probably idle with well over 20psi pressure. Your engine is of an age where there may be some loss of oil pressure due to age but I can assure you there is little need to worry as long as you have perhaps 10psi on hot idle. Are you sure your data is not the pressure relief valve setting? I have just looked up the data for my Bukh (all modern engines have similar internal designs and must comply with the same physical laws) and the relief valve setting just happens to work out as 14.2psi and the oil pressure switch will be set to less than that. I am convinced that you do not need to worry about the calibration of the switch and I know there is no way they can set to 0.2psi on a mass produced item such as the switch. Is it possible to fit an elbow in the block so the switch lies parallel with the engine block? Is there an alternative position that has a plug in its a present (our training Kubota has its oil pressure switch at the back end of the block, well away from the starter), and have you tried the Agricultural Kubota agents? Tony Brooks