Hi i need advice here ( and yes I have searched extensively and not found anything specific to the M606 unit which is different to the tacho senders on the older ones in the posts I have read).

I think my tach sender might be dud as my tacho is intermittent and so is my A/C.

So far:

I found a two core cable coming through firewall into duo valve area with plug and socket. when i broke this the tacho stopped completely so I think this must be the sender cable.

First question: I measured the a/c voltage on the pins with the engine running and it hovers just below 5v - is this about right?

second question: The cable dissappears downwards behind the the oil filter housing . How do I get to the tacho sender to remove / clean and do further tests? do I have to remove the oil filter housing or inlet manifold to do this? or is it possible to get at it from below? I dont even know what it looks like or how difficult it will be to find/remove.

If the tach sender checks out OK what else could cause both the tacho and A/c to be intermittent ?. My thoughts are Klima (but this wouldnt affect the tachometer or would it?) or EGR relay? I have already tested OVP and its ok.

any advice really appreciated as I am keen not to buy parts until I am sure I have isolated the item at fault.

thanks in advance
Keith