Oil pressure light

[JumboBeef]

I asked this question elsewhere, but it got a bit lost in other replies.

The oil pressure light on my 400 doesn't work.

If it is the bulb, how can I access it?
What else could it be if it isn't the bulb?

Thanks.

[Yatesy350i]

Hi Mate

Not sure on a 400 but on my 350 I was able to just remove the front wood trim and then prise the lamp holder out if the metal dash plate. There was enough slack on the cable to allow the lampholder to be pulled forward enough to change the bulb.

Karl

[ElvisWedgely]

Ok. This is how the oil light works. Power is supplied to one terminal of the bulb when the ignition is switched on. The other terminal from the bulb goes to the oil sensor on the side of the front side of the engine. The oil sensor is switched on earth position when engine is off so makes a circuit to the bulb and the light is on in the dash. Once the engine starts up, the engine oil pressure cuts the earth circuit by pressurising the oil sensor, so the oil light on the dash goes off.

To fix the problem you have to use elimination. If other warning bulbs are working on the dash, then it's not the fuse. Next you can eliminate the sensor on the engine. From the terminal on the back of the sensor, run through a bulb or tester light to the positive on the battery with thd engine off, should light the test bulb. Then start the engine and the test bulb should go off if the oil sensor is functioning. This then eliminates the oil sensor. Now, you only have the bulb in the dash and the wiring remaining. Next, I would change the bulb. If it still doesn't work, get a beer out the fridge, sit down and drink it before you start looking for a broken wire between the bulb an the ignition, or the bulb and the oil sensor. This all sounds a lot of work, but in actual fact it's quite easy. It's ususlly a faulty bulb anyway, and if you replace the bulb, make sure you get the correct wattage etc or you'll create more confusing problems.

I hope all that makes sense. Oh, and to access the bulb on a 400, you should be able to reach from under the dash. If not, there are two screws I believe on either side of the small dash which has to be undone from the rear and it is probably harder to get to them than reaching the bulb from underneath. Good luck

Tony.TCB.

[JumboBeef]

Thanks! I'll take a look.

[JumboBeef]

How do you get the bulbs out? Are they pull, pinch or twist?

[JumboBeef]

JumboBeef said:

How do you get the bulbs out? Are they pull, pinch or twist?

Anyone, please?

[ElvisWedgely]

From memory I think they are twist and out but I'm not absolutely certain. They could be pull out but I doubt they are pinch. If you are doing this from under the dash, it's quite easy once you manage to reach the bulb holder as it can be done by feel. Try twisting it first as I believe that is what they are. You need small hands, lots of space between seat and dash and you need to be a part time contortionist. The other alternative is to take the small dash in front of driver out but similar obstacles apply. If you don't want to do any of these, you can wire a new bulb and holder somewhere convenient under the dash which is probably much easier to do. Sometimes in a TVR changing a simple thing like a bulb can be harder than changing the clutch. Good luck.

Tony.TCB

[mtb]

Just replaced my bulb on 350i removed veneer to access smoked plastic cover over warning lights then with a tiny screwdriver flicked the red plastic bulb cover out........pair of long nosed pliers bulb twists anticlockwise mine is a 12 volt 2watt cleaned glass on gauges jobs a good in just over a hour.


Mike

[JumboBeef]

Thanks for the replies.

mtb said:

Just replaced my bulb on 350i removed veneer to access smoked plastic cover over warning lights then with a tiny screwdriver flicked the red plastic bulb cover out........pair of long nosed pliers bulb twists anticlockwise mine is a 12 volt 2watt cleaned glass on gauges jobs a good in just over a hour.


Mike

Can you get them off the shelf at somewhere like Halfords?

[adam quantrill]

Before messing about with the bulb, take the wire off the sender switch, ignition on, engine not running.

Touch the wire to the engine block and (get a mate to) check if the bulb lights up. This will tell you if it's actually the sender that's knackered and it only takes 2 or 3 minutes.

[JumboBeef]

Thanks.

Dumb moment: is the sender the round thing with one wire coming out from it at the front, on the driver's side of the engine?

If it needs replacing, where could I get a new one?

[JumboBeef]

So, I got the multimeter out and checked continuity between (what I believe to be) the oil pressure sender and earth. Nothing. So, that must mean I need a new sender......?

Then I connected a wire between the wire going to the sender and earth (with ignition on).................and the bulb still didn't light up.

Confused.

Edit: I am a muppet with no intelligence.

I was sticking the multimeter on the back of the sender for the gauge. When I stick in on the sender for the light, I got continuity, so that proves the sender works. When I connected the connector from the bulb to earth, the bulb doesn't light up.

So, I'm back to checking the bulb. I just can't see how to get the bulb out. I can touch the back of the housing but I cannot feel any wires or anything to remove to get at the bulb.

Edited by JumboBeef on Friday 6th June 10:54

[ElvisWedgely]

Sounds like the bulb or its power supply. Getting the bulb out is a nightmare. On the 400 you should be able to get to it from the back but it's very difficult. You may have to remove the small dash section where the speedo annd tacho are. Again very difficult to do, especially if it hasn't been removed for a long time. I belive there are two screws behind the dash, one on the left and one on the right. Very difficult to get to and undo. That's why the bulb hasn't been replaced by previous owners. When this job is carried out, some people put the small dash back loosely so as removal is easier the next time. You could always wire in a new bulb and holder elsewhere, much easier to do and save you taking the dash out. Then one day when the dash is removed for a bigger job you can change it then.

Tony.TCB.

[JumboBeef]

ElvisWedgely said:

Sounds like the bulb or its power supply. Getting the bulb out is a nightmare. On the 400 you should be able to get to it from the back but it's very difficult. You may have to remove the small dash section where the speedo annd tacho are. Again very difficult to do, especially if it hasn't been removed for a long time. I belive there are two screws behind the dash, one on the left and one on the right. Very difficult to get to and undo. That's why the bulb hasn't been replaced by previous owners. When this job is carried out, some people put the small dash back loosely so as removal is easier the next time. You could always wire in a new bulb and holder elsewhere, much easier to do and save you taking the dash out. Then one day when the dash is removed for a bigger job you can change it then.

Tony.TCB.

Thanks.

I'm sort of thinking I don't really need it, as I have an oil gauge anyway......