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[luv_my_mv6]

Evening all, fixed my temp guage today (dodgy sender at back of engine), but now I have an even more alarming problem..... the fuel guage has now started playing games, when ignition is on but engine off, it is accurate, but as soon as I turn engine on, the needle drops slowly down to the empty mark (fuel warning light doesnt flash and MID is still saying aprox the correct range for the fuel I have) Its as though the voltage is slowly dropping as soon as engine is running...... any ideas anyone (dont really want to swap dash boards as I like my calibrated speedo  ) Speedo, rev and coolant temp are all working fine.

[Kevin Wood]

Hmm. Interesting one.

Only things that come to mind are that the voltage regulator inside the gauge has failed in some way, although I would imagine this is combined with the rest of the dash electronics, or that the signal from the float in the tank to the dash is getting upset by additional loads on the electrical system when running, perhaps due to a dodgy negative connection to the vehicle body either somewhere near the fuel tank or under the dash area.

It might be that the float sensor shares a negative connection with the fuel pump, for example, as these are both located in the tank. A bit of voltage drop here could well upset the gauge without seriously affecting the fuel pump operation.

I'd check the wiring around these areas and failing that get a Tech2 on it. It's possible that a Tech 2 can look at the sensor readings seen by the dash and can see if that is also changing when the engine is started.

Just another thought. Try measuring the battery voltage when engine is both stopped and running at a fast idle. It could be that you have a faulty alternator that's generating too high a voltage and that's causing the gauge to malfunction when running.

Kevin

[luv_my_mv6]

hmm cheers kevin, will try and get it checked by tech 2 after my mot if it passes  

[Marks DTM Calib]

Check the earth point in the boot, its behind the plastic trim below the boot slam panel.

[luv_my_mv6]

  Thanks MDTM, had a look but everything ok, good clean contacts, so just got a dash from scrapper, need the mid and fuel guage out of it, both working so gonna put the good bits into my own dash cos.
 You guys could make your own version of haynes and make some serious money you know, your knowledge is priceless, thanks again
 John