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PostPosted: Wed Nov 30, 2016 8:25 pm 
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A bit of a wierd one this. Suddenly the boost gauge in the instrument cluster goes up to full boost on turn of ignition key and stays there.

Anyone had this before? I suspect it is just a an instrument cluster issue as the car runs and doesnt fuel cut!

Battery voltage was low and I've seen instrument oddities before due to alternator issues so maybe linked?

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PostPosted: Wed Nov 30, 2016 10:12 pm 
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I have heard of this before and it being alternator related. Might be time for a trip to Burghfield.

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PostPosted: Wed Nov 30, 2016 11:19 pm 
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I've had the boost gauge go erratic on my 205, sometimes indicating full boost as above, sometimes working correctly. Again, engine operation was fine so not a sensor issue.

Check the alternator voltage with a multimeter to see if that's the problem. I suspect it's more likely a poor connection or gauge problem, maybe the instrument cluster earth.

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PostPosted: Wed Nov 30, 2016 11:25 pm 
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Alternator appears to be outputting a steady voltage of around 13.8V.

The problem seems to have gone again now after a bit more charge and startup again after a couple of hours. Maybe it didn't like the jump pack?

This has kind of coincided with a start of sporadic speedo failure (then it gets better again!) so I will pull instrument cluster and check as well.

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PostPosted: Thu Dec 01, 2016 6:00 pm 
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Subscribing in case there are any eureka moments in this thread

My ST205's OEM boost gauge is still inverse reading.

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PostPosted: Thu Dec 01, 2016 8:13 pm 
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I never bothered sorting my 205, though I suspect the gauge itself as all other things work ok.

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PostPosted: Thu Dec 01, 2016 8:15 pm 
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Just a thought. Could there be some form of capacitance, that if the battery is very depleted, cause false readings ?

Emicen, could you have a connector the wrong way round ?

I am ready to be shot to bits, as said before I am just thinking

Hopefully it all sorts out the faults

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PostPosted: Thu Dec 01, 2016 10:45 pm 
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As I understand it the MAP sensor has a 5V feed from ECU and returns a voltage between 0-5V with circa 4.2V being around 17psi and low voltage being vacuum.

As such if you stuck 5V up the dash boost gauge it would think it had "mega-boost" so is possible if somebody has been ahem fiddling with wires. I guess there are other cocked-up scenarios that would cause a similar issue but you'd have to get a multi-meter on the dash cluster to measure the voltages.

If the ECU was seeing the same voltage it would fuel cut unless sombody had installed a fuel cut defender.

My theory is that it must be an issue dash cluster end or an anomaly with low battery.

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