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Boost Gauge - Figure is erratic

AdrianL

Active Member
Nov 27, 2013
74
0
Batley, W Yorkshire
Hi All,
I fitted a boost gauge today but I don't think it's working quite right... it's an electronic one.

When the engine is NOT running:
The gauge itself lights up fine, and if I power up the gauge without a connection to the boost sensor, then it shows -14 (should it show 0?). When I connect the sensor, and both have power, the number seems to be around 3? but jumps around a bit.

When the engine IS running:
Again, gauge lights up fine. When the sensor is connected, I see negative figures, but generally not above 0. Boosting doesn't seem to effect the figure, it just jumps around (but it jumps around when idling too).

To me, it looks like there is something wrong with the boost sensor... but I don't quite understand why the gauge is saying -14 without the sensor hooked up?

I routed the wire through the engine bay into the cabin, but I think tomorrow I will try a new, shorter piece of wire straight to the gauge and see if I get different results...

It's this one on Ebay: 360742160624

Thanks,
Adrian
 
Last edited:
shnazzle said:
Negative numbers tend to not go above 0.

Sure you connected the vacuum/boost tube correctly to the sensor and an appropriate place on the engine?
Also, is the sensor powered correctly?
Click to expand...

As far as I am aware, yes, as I followed the guide here:
seatcupra.net/forums/showthread.php?t=214493

There is an in-line 'air filter' that came with the kit - but presumably this shouldn't cause what I'm experiencing?

I took a feed from the fuse box using a fuse tap, and I've used a ground under the dash, so the power is definitely there. The wire I used to extend the sensor and gauge is a bit thinner though... I think the conductor/strands inside the wire are about the same size but the insulation is certainly thinner - could this be to play?
 
The filter is fine, supplied with most kits. Don't want yucky air going into your sensor :)
The wire sounds fine, although it might have a higher resistance causing weak readings.

When your engine is running it will be running vacuum, but it should be at 0 when it starts up with no engine running. Boost readings should also just be smooth.
Check the manual/leaflet that came with the gauge. I remember mine said something about what's wrong if it's showing wrong numbers.
 
Cool :).
I'll try find some thicker wire and hook it up to see if there is a difference.

It's certainly not at 0 when the gauge & sensor are powered but engine is off. The readings were just erratic when driving... nothing smooth about them.

Unfortunately there is no troubleshooting in the leaflet :(

The only thing I can see to check at the moment then is the wiring?
 
I can see if I can dig out the leaflet that came with mine to see what it says. Should be the same-ish. Mind chances are thicker wire will have more resistance.
 
Haha well the best wire is the one that matches the one that you're extending. But it doesn't need to be that specific I think.

I just looked at my sheet and it doesn't have the info. Must have imagined it...odd
 
shnazzle said:
Haha well the best wire is the one that matches the one that you're extending. But it doesn't need to be that specific I think.

I just looked at my sheet and it doesn't have the info. Must have imagined it...odd
Click to expand...

Damn. OK well I'll try some different wire tomorrow. Failing that I'm lost :(.
 
Right, well I tried a new piece of wire (That is the same thickness as the gauge wire), and it made zero difference. I also used a multi-meter to check that the sensor is getting power, and it is... 12V...

Here's a picture of how I've set it up, this is correct according to the guide I used:


High res: http://i.imgur.com/ZqiD2Ri.jpg

Apologies for the crude wiring / tie wraps. I was going to tidy when I had it working..


Is it possible the air filter is the wrong way round? a mate suggested it could be a one way valve...

Although, this still wouldn't matter as the reading on the gauge is -4/-3 when the engine is OFF... when it should be 0. Looks like the sensor doesn't work then?
 
Last edited:
Well, my mate had a spare Greddy boost sensor laying around and I gave that a go.... and it worked! woohoo. So just a dodgy sensor thankfully. You can get universal ones off ebay too for around 15 quid.

Also worth noting is that the figure was still around -3 when the engine was off, but after turning the engine on and back off it went to 0, so I think it could have been some air in the pipes or something?
 
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