Oil Pressure/Level Gauge

[Way2go]

Has anyone with electronics knowledge investigated/dismantled the oil pressure/level gauge (may be applicable to Matt F or Electrokid)?

My gauge is exhibiting odd behaviour when the sun is out! The light may stay on & it reads level continuously with the light on or it will go out and read pressure as it should but then the light may come back on and it will continue to read pressure. In the evening when the car is cool the gauge will behave itself.

So, my feeling is that a component in the gauge electronics has gone temperature sensitive - any ideas what and is this fixable without finding another gauge which is presumably also a hens teeth item?

[bx petrol auto saloon]

Dear W2G,
Firstly, my BX doesn,t have one of these gauges. My Rapier did and the gauge was fed by a small bore plastic pipe connected to the cylinder block by a brass type adapter.
Are you a 100 % sure that your problem is to do with a faulty gauge, and not due to a faulty oil pressure swicth
Vince,

[mat_fenwick]

It doesn't sound like the sensing part of either circuit - rather the timer circuit which decides which reading (level or pressure) to display on the gauge. I haven't had to investigate the circuit, but out of curiosity did have a look at it once a few years back and it was all fairly simple with though hole components, and hence easier to diagnose. A dry joint might be what will be suggested but personally I can't see why that would suddenly become a problem after 20 odd years of working satisfactorily.

Maybe a component not working correctly when hot? I can't remember for sure but is there a relay click when the mode of operation switches? If so it could be a simple mechanical problem (wear and tear) with the relay, or a problem with the transistor which (presumably) switches it. I'd be reassured by the fact that both gauge functions themselves seem to be OK, which limits the part of the circuit to diagnose.

[citronut]

i didnt know the gauge read oil pressure but just the level,

the usual fault with the level indicator is the sensor gets clogged with carbon,

the sensor is located at the back of the engine block,

were as the oil pressure sensor is on the front of the engine block

regards malcolm

[mat_fenwick]

i didnt know the gauge read oil pressure but just the level,

It's only the higher spec. models which did the pressure too - the rest the gauge just sits idle after the light goes out.

[Way2go]

Maybe a component not working correctly when hot? I can't remember for sure but is there a relay click when the mode of operation switches? If so it could be a simple mechanical problem (wear and tear) with the relay, or a problem with the transistor which (presumably) switches it.

Thats my thought too, that it could be a faulty timer (555?) but the relay thought is good as this could explain the separation between the light circuit and meter switchover. Maybe there is a miniature relay on the meter gubbins. I seem to remember that it was slightly bulky with a white shroud on the back of this gauge when I've attended to the speedo and changed lamps.

I was hoping someone may have one out of the car to look at to decypher - it's a pain to dismantle the dash for analysis and still be able to use the car when needed. If you know in advance what circuits/components are within it to investigate you can drastically reduce the time out of service.

[Way2go]

i didnt know the gauge read oil pressure but just the level,

It's only the higher spec. models which did the pressure too - the rest the gauge just sits idle after the light goes out.

It's actually quite addictive viewing when idling and driving. When cold the oil pressure is the same as driving but when warm idling will be a couple of points below driving. To see the pressure indication reassures you more than the level indication really.

[Way2go]

Dear W2G,
Firstly, my BX doesn,t have one of these gauges. My Rapier did and the gauge was fed by a small bore plastic pipe connected to the cylinder block by a brass type adapter.
Are you a 100 % sure that your problem is to do with a faulty gauge, and not due to a faulty oil pressure swicth
Vince,

Hi Vince, you are thinking pre-decimalisation with a Rapier aren't you? Those were aneroid mechanical gauges. These are electronic gauges coupled by wires to senders on the engine. The gauge itself is OK because it is reading but it has associated circuitry which is causing the described problem.