Boost Gauge Off Scale.

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Boost Gauge Off Scale.

Postby lotusflasherman » Wed 24.06.2015, 18:06

Just driven home with my Boost Gauge showing around 0.4 bar boost on light throttle & low revs and then went off the scale when I stopped on my drive. 'Engine off & ignition on' gave me this
offscale.JPG

I was a bit worried about it damaging the gauge so thought I'd pull off the supply from the Boost Pressure Transducer but it obviously works in the other direction as it stayed the same. Then I noticed the bottom screw was loose allowing a 'floating earth' and a few turns to tighten it up and every hunky-dory again. Offending screw shown in this one..
bpt.JPG

Just thought I'd share...
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Re: Boost Gauge Off Scale.

Postby Saltire » Wed 24.06.2015, 19:11

Thanks, Phil, off to check the offending screw now :)
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Re: Boost Gauge Off Scale.

Postby pmb » Mon 13.07.2015, 13:29

Tick another box in the "success" column for tightening the ground screw! Erratic gauge operation completely tamed by a simple turn of the screwdriver.
Many thanks to the knowledgeable contributors on this forum.
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Re: Boost Gauge Off Scale.

Postby sinannasirli » Thu 14.07.2016, 23:10

Any ideas if the following happens and if you have a good ground?
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Re: Boost Gauge Off Scale.

Postby John_W » Fri 15.07.2016, 11:35

Any time I've seen people reporting a "boost off scale" problem, it has always been to do with a faulty earth connection at the transducer, as lotusflasherman's photograph shows.
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Re: Boost Gauge Off Scale.

Postby sinannasirli » Fri 15.07.2016, 11:46

I did make sure that there is good ground.. Measured with multimeter... from the bracket to iback of the gauge..

It has ground.. I am going to get crazy....

Next thing i will do is to take the transducer apart.. or try with a new transducer..

MIne is an S2 car but the transducer is orange instead of grey, so somebody have messed up with it already, as they told S2 transducer is grey..

Regards

Sinan
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Re: Boost Gauge Off Scale.

Postby dapinky » Fri 15.07.2016, 11:51

Sinan,

As others have stated, the issue is usually with the earthing of the transducer.

I know you have checked continuity to the guage earth, but when this happened on one of my cars and I couldn't see what was happening, I ran a seperate earth wire between the transducer and the earthing point at the bonet hinge. This solved the problem, but I still don't understand how it made a difference as (like you) I had already checked the full continuity of the circuit.
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Re: Boost Gauge Off Scale.

Postby lotusflasherman » Fri 15.07.2016, 21:32

sinannasirli wrote:I did make sure that there is good ground.. Measured with multimeter... from the bracket to iback of the gauge..

It has ground.. I am going to get crazy....

Next thing i will do is to take the transducer apart.. or try with a new transducer..

MIne is an S2 car but the transducer is orange instead of grey, so somebody have messed up with it already, as they told S2 transducer is grey..

Regards

Sinan


My photo at top of this thread is a grey transducer on a '93 SE , so it may be an early or late issue ... earlier SE has orange and think I have a spare orange, but don't think colour is important. Working properly is.
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Re: Boost Gauge Off Scale.

Postby sinannasirli » Sat 16.07.2016, 00:54

İs it possible for you or for anyone else to measure the resistance between G terminal and earth of the transducer?

What is important, it shouldnt be hooked up to the gauge when measuring, at least not the G terminal..
Maybe measuring any spar s you might have?

do you have connectivity with some resistance or no connection?
Thank you

Sinan
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Re: Boost Gauge Off Scale.

Postby lotusflasherman » Sat 16.07.2016, 21:06

sinannasirli wrote:İs it possible for you or for anyone else to measure the resistance between G terminal and earth of the transducer?

What is important, it shouldnt be hooked up to the gauge when measuring, at least not the G terminal..
Maybe measuring any spar s you might have?

do you have connectivity with some resistance or no connection?
Thank you

Sinan


Sorry I can't for a while. I'm in south of France, Elan is in UK. Mr Pink is good at these things..... Dave?
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Re: Boost Gauge Off Scale.

Postby sinannasirli » Sun 17.07.2016, 21:21

I did make the test with a friends car.. I was right and transducer is at fault.. So I am the unlucky one out of the all remaining people with a grounding problem..

If anyone bumps into a similar problem, here is how to troubleshoot with a multimeter..:

viewtopic.php?f=35&t=25442

Regards

Sinan
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Re: Boost Gauge Off Scale.

Postby shakadad » Sun 11.03.2018, 01:14

Wow I just had my boost gauge stick up at max when turning the car on. This thread seems to have it solved, I'll go out to check that screw now.
Video of Gauge jumping to max...
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Re: Boost Gauge Off Scale.

Postby lotusflasherman » Sun 11.03.2018, 18:40

shakadad wrote:Wow I just had my boost gauge stick up at max when turning the car on. This thread seems to have it solved, I'll go out to check that screw now.
Video of Gauge jumping to max...


Hope tightening that screw sorts it out for you ...
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