Morris Minor Owners Club

Shame that you did'nt suggest this befor it would of saved time, seeing that you seem to be quite an expert

I've always used a spanner but perhaps your switch is different to the ones I've seen.

Just a bit of theory and a recap to clarify where I think we've got to...

For the purposes of this post, we'll not worry about whether the car is positive or negative earth, nor about which direction the electrons are flowing; the theory remains the same:

When the ignition is turned on, power flows from the battery, through the ignition switch and into the warning light in the speedometer. From there it goes down an earth wire that is connected to a switch. In this case, it's the oil pressure switch mounted near the back of the engine. When there is no or very low oil pressure, then the switch closes and allows current to complete a circuit, earthing in the engine. This illuminates the warning light. As oil pressure increases, the switch opens and as current can no longer flow, the light goes out.

There are numerous different "body" styles for the oil pressure switch, but they all work in the same way. Most have a hexagonal base between the screw thread and the larger round body. This will accept an open ended spanner. Other sorts need a large pair of pliers on the body. Some years ago, there was a batch of notoriously unreliable switches on the market - I had to fit three in a row before I found one that worked. When the warning light comes on, it is usually the switch that has failed. However, don't rely on it, it could be very expensive!

Always check the oil level, but change the switch (preferably with a known good one) and see if the warning light goes out. If not, then you need to worry about the mechanical side of things. If the light goes out, then problem solved.

Note: when fitting the new switch, do NOT use PTFE tape or similar sealants, the switch needs a good contact with the engine block. The thread is tapered, and should seal easily as the switch gets tight whilst being screwed in.

The unit at the front of the engine below the thermostat housing is a temperature sensor of some sort. It works in a similar way in that when the engine is cold, then the "switch" is open and the light does not come on. as the temperature rises, the switch passes more current, either allowing a light to come on, or a gauge to show a rising temperature. Landrover used to fit a switch in series with another switch on the choke. If you pulled the choke out, it passed current to the temperature switch. When the eginer got warm, the switch closed and illuminate a light to remind you that the chole was still out.

In your situation, the best thing to do is to disconnect the wire from the temperature sensor so as to eliminate it from being the cause of the light that your are interpreting as the oil pressure warning.

The warning lights in the speedo can easily be swapped over from left to right and vice versa, so you cannot rely on the glowing light being what you think it is! To help prove it, once the light is on, pull the wire off the oil pressure switch. If the light goes off then that's the one about which you are concerned.

Hope that helps. Good luck.

Wow, thats more than clear, thanks alot for this full information, really helpful stuff.

If you use a 'monkey wrench' or 'stillsons' on the switch - you will ruin it. This is NOT the way!! It WILL have flats on the shank that screws into the block - and that's how you unscrew the switch - but I have already told you I really don't think you need a new switch - and suggested some very simple tests you could perform to check this. Have you bothered to try these tests ? I notice you are resorting to your previous belligerent/smart style of post ! Is this really necessary ? Folks on here are trying to help you - yet you don't seem willing to help yourself.

Personally I find it hard to understand you at times. You seem to be at all times hard when maybe you should be more relaxed and calm, even if I am sure that your only goal is to help. At this moment I am just collecting as much info as possible and then will make a decision, even if i ruin the switch, makes no problem, I am intentioned to instal a new one. regarding your suggestions to test the switch, well as soon as I can I will do some testing, you see unfortunatly I do not have my morris underhand, but I have it parked outside Paris, I don't have a closed garage here in the city, and only leave the city from time to time, work reasons. And thats another thing, I try to collect as much info as I can also because its impossible to find any kind of assistance or help here in France, its impossible, so all that has to be done is done by myself, and at times, only those who are no scared of making mistakes finally get to learn somthing more.

Ah well you see - you didn't say anything about being in Paris before! Although I did detect some language difficulties. You should post up your location in your profile. I still don't think you need a new oil pressure switch. Let us know when you have done some testing.

joeone62 wrote:Personally I find it hard to understand you at times. You seem to be at all times hard when maybe you should be more relaxed and calm, even if I am sure that your only goal is to help. At this moment I am just collecting as much info as possible and then will make a decision, even if i ruin the switch, makes no problem, I am intentioned to instal a new one. regarding your suggestions to test the switch, well as soon as I can I will do some testing, you see unfortunatly I do not have my morris underhand, but I have it parked outside Paris, I don't have a closed garage here in the city, and only leave the city from time to time, work reasons. And thats another thing, I try to collect as much info as I can also because its impossible to find any kind of assistance or help here in France, its impossible, so all that has to be done is done by myself, and at times, only those who are no scared of making mistakes finally get to learn somthing more.

i'll agree with you. it's irrelevent to you and me about the price of a new switch. £4 isn't it? the price of a beer!

get some grips and pull the switch off. almost any replacement one for an A series will fit. it's not a difficult job. once you've replaced it, you'll have a sound mind.

well as suggested by someone I checked the wireing from the oil pressure switch to the warning light on my speedo, and I was surprised at what I found out. Well on the bulb holder there are two wires of which one infacts leads to the oil pressure switch, that is normal, but the second wire lead to the temperature switch, and this was a surprise. Maybe the thong that I cannot figure out is that when the engine is heated up the warning light comes on???? Could it be that both switches are connected to the same warning light??? Has anyone an wiring diagram from a later morris, lets say late 60s, because the ones that I have are fairly early, infact they don't even indicate the voltage stabilizer for the fuel gauge

The wiring diagrams are in the Workshop Manual - and NONE have or ever had a high temperature switch! Looks like someone has been messing about with your wiring............

Could it be possible that the engine is from a mini. I have been doing some research and I have found out that the engine used by the mini had the two switches, could this somehow be possible.

No - the 'engine' could not be from a Mini - but the cylinder head could be - but 1098 Minor heads had a place for a sensor anyway. . Yes - many Minis have temperature gauges - but NOT 'switches' that suddenly bring on a light when they get too hot! However - it is possible someone has just connected to the temperature sensor - and has discovered that the resistance of that sensor falls off steeply as it warms up - and eventually brings on the light brightly enough to be seen! It's possibly glowing feebly when cold -and getting bright when hot. But that doesn't mean it is overheating.............

Well finally I checked the wireing and noticed that that orange light is conected to the tempture valve and not to the oil pressure switch. I disconnected the wires and the only went off when disconnecting the temp wire to the switch, looks like its a mess what do you think

Put the wiring back to what it should be. Ignore any wires to the temperature sender (disconnect the wire at both ends). On the voltage stabiliser, the input will probably have two wires: One comes from the switched ignirion circuit, the other can be used to feed the oil pressure warning light. The other terminal on the stabiliser will feed the fuel gauge. Make sure that you are picking up power from the unstabilised side. Now take another wire from the warning light and connect it to the oil pressure switch. Your wiring is now how it was intended to be; and should be OK. If the warning light still comes on (after changing the switch) then you do have a problem, but I suspect that all will be OK.

Thanks for this info, I wa thinking on the speedo when you turn the ignition key should two lights light up, the red generator light and the orange oil pressure light come on before starting the engine, is that correct

Thanks for this info, I wa thinking on the speedo when you turn the ignition key should two lights light up, the red generator light and the orange oil pressure light come on before starting the engine, is that correct

Can someone tell me what engine this is also because i have a feeling that there is somethings different, as for example the copper water hose is on the wrong side of the ehgine.[frame][/frame]

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It sure looks like a standard 1098 to me, or a 948 with a different head than it came with. If by 'copper water hose' you mean the one shaped like this...
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...on the left side of the engine as viewed from rear, next to the block, which carries water from the interior heater back to the radiator/cooling system -- this pipe is on the correct side of the engine (and indeed, based on the standard setup of the 948 and 1098, it is impossible to place it on the other side).

I have often been found wrong before, but I believe things in your engine bay are all right. Understand that without seeing it in person, it's difficult to know...

Also, from what I hear and have seen, the IGN and OIL lights on the speedo should light when the key is turned. (My OIL light is green, but orange is correct after about '60.)

All looks normal to me....