Morris Minor Owners Club

My 'Oil Filter Blocked' warning light has come on. I've read the existing threads on this but nothing quite addresses my situation which is as follows:

I changed the engine oil and filter about 200 (two hundred) miles ago. When I did the change, there were two parts missing from the oil filter assembly which I have now replaced, namely; the small metal washer immediately above the spring and the rubber washer above that. The larger dished metal plate which now sits on the rubber washer was, previously, in direct contact with the spring with there being very little to prevent oil passing out through the centre of the plate without being filtered. I'm quite confident that I have fitted the filter correctly (but there is always room for doubt since I'm an amateur mechanic!). The 'Oil Filter Blocked' warning light has now come on. It is on at all times, including when I switch on the ignition but the engine has not yet been started. Note that the 'oil pressure' warning light continues to operate normally (i.e. comes on when ignition is switched on and goes off immediately the engine starts).

I find it odd that the 'Oil Filter Blocked' warning light comes on when the ignition is on but with the engine not running and I'm noting that it never used to do this. I am under the impression (I could be wrong) that the switch works on the pressure difference between the oil entering and leaving the filter and operates when the pressure difference is too large, as it would be if the filter were blocked. I am wondering why the warning light comes on when the ignition is first switched on as any pressure difference must surely have drained away at that stage.

Thanks for reading. If anyone does have any suggestions as to what might be wrong I'd be very grateful to read them. I've dismantled and re-fitted the filter but this has made no difference. Also, as a check, I temporarily removed the wire going to the top of the oil filter so I'm now quite sure I know which warning light is which.

Thanks again,
David

Must be a short in the wiring - or a faulty 'blocked' switch on the filter head. Unplug from the filter head to check which...

You are correct in that the light should be off at all times unless the filter is blocked. There is no "self test" in this very simple circuit; so it is either faulty wire or faulty switch. Unfortunately the filter heads with the switch are no longer available. I have never tried to strip one to see if the switch can be serviced.

Another useless light to worry about. It cannot be that important or they would have fitted it to more cars. Since I have a cannister conversion I have no provision for the warning light so the end that was connected to the fiter is now connected to the flasher unit and the bulb operates as the trailer indicator warning light

Of course - are you SURE it is the blocked filter light? Maybe it's the 'Low Oil Pressure' light or the 'No charge' warning light. Check urgently before running the engine again....

Thanks to everyone for the help.
I'm perfectly sure it is the 'Oil Filter Blocked' light and not the 'Oil Pressure' light; I temporarily disconnected the the wire from the terminal on the filter head and the light when out (this action also served as bmecosse's check for short circuit vs faulty switch). Also, the 'Oil Pressure' light is continuing to work normally.
In short; I fairly sure I haven't got my wires crossed and it looks like it's a faulty switch.
Thanks again (I love this forum!).
David

So did the blocked filter light go out when you disconnected the wire at the filter head?
I'd asume it's just a basic pressure switch that if it senses too much pressure it operates and brings on the light.
If it didn't do it before (coming on with the ignition) and it does now it looks like a faulty switch. The filter is all assembled ok I take it and not operating the switch itself all the time is it?

ah just seen your last post, light out when disconnected is faulty switch OR assembled wrong maybe.

Thanks MrIan.
I agree that the 'wrongly assembled' possibility still exists. However, it seems like an almost vanishingly small possibility given the design of the filter assembly. I can see how I might wrongly install the new filter to give no filtering but I can't see a way of getting it wrong such that it behaves as if it's blocked. That's why I think that it's a faulty switch.
I'd be Interested to know if you disagree.
Thanks again

I'm not sure on the assembly so I'm not meaning to say you've assembled it incorrectly, it's just me thinking of reasons for the fault. So as long as you're sure it's assembled ok and the light is off when the wiring is disconnected from the switch it must be a faulty switch.

I would inspect the filter assembly - in case it really HAS become blocked. In which case it could be seriously starving the bearings of much needed oil pressure...........