Oil Pressure Gauge

[mikeanson]

I know it's not a real gauge, but a stepper motor driven indicator - trouble is, mine is playing up. Has anyone had any experience of fixing these? I don't want to send it away, as I can probably fix it myself, but I have no information on how it works! Basically, it seems reluctant to reset to zero with ignition off. Consequently, starting the engine puts the needle way past the top of the scale. The behaviour is not consistent though and occasionally it works as expected. The oil pressure warning light goes on and off as expected so I don't think it is the pressure switch. I might have to take the gauge out and have a fiddle in the absence of any info.

[Astromorg]

The first thing I'd try would be a battery disconnect/reconnect. If that had no effect, it is possible, using care, to move the gauge needle manually back to it's stop and if that doesn't work try another battery reset with the needle in its correct position on the stop.

Another avenue to pursue would be to check the wiring between where it plugs into the rear of the auxiliary panel and the yellow connector into the front of the main instrument panel. That yellow connector has a special type of clip that pulls the connector into full engagement and then clips itself to prevent it loosening if it's properly assembled.

Whether the pressure switch is creating the problem can be checked by unplugging its connector and temporarily connecting the orange/yellow wire to a good ground point with ignition On.

[mikeanson]

Thanks Astromorg, I tried battery disconnect which didn't help much. It's like the stepper doesn't always get set back to zero when engine is turned off, but sometimes it does work correctly. I have ordered a used replacement from Auto Reserve and have a play with that! I can replace the stepper if that is the problem once I know what to get.

[mikeanson]

I bought a used minor gauge panel and plugged it in. The gauge works correctly, so I know the pressure switch and everything else is in order. Dismantled the used panel to see how it went together before working on mine. The problem with attempting to replace the stepper is that the stepper motors are all held in place by 2 screws which come from the front and are then covered by the dial plate which is a thin piece of plastic glued on to the assembly. If I attempt to remove this plate to get at the screws, the plate is bound to get damaged. So, for the moment, I am stuck. I didn't want to simply swap the panels because the used one is from a much older car and the steppers could ultimately fail in the same way.

[mikeanson]

Update: It is possible to peel back the dial gauge sheet carefully and access the screws. A bit of heat to help mobilise the glue and it came away nicely. New stepper motor fitted and works a treat! The failure of the old one was because one of the windings was open circuit. I might write this up for the magazine if they are interested.

[ptjs1]

Good investigative work, Mike! Well done!

I'm sure an article in the mag with some pics would be well-received by members!

Paul

[JimMann]

Hi Mike, as the person responsible for compiling the monthly column for the Modern XK Section of the magazine, I can assure you that a write up and accompanying photos would be welcomed. You will find my email address at the top of the Modern XK pages in the magazine, so drop me a line and I can offer some guidance if you need it.
Jim Mann