russtik
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| posted on 20/8/15 at 02:04 PM |
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Speedo reading erratic (Acewell digidash)
I've got an Acewell digidash fitted to my car which was faultless until recently when the speedo reading started jumping about, suddenly showing
nearly twice the actual speed, then back to normal, then something like 7MPH... it's all over the place. the speed sensor is at the diff input
flange, with the magnet on the flange. It's all still mounted securely and there's approx. 5mm gap between the magnet and the sensor. The
magnet centre isn't perfectly inline with the sensor but it's only a couple mm out, I can't imagine this would cause this issue and
it would have been like that before when it was working fine.
Any ideas what could be causing this sudden erratic behaviour?
[Edited on 20/8/15 by russtik]
SouthernKitCars.com
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tims31
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| posted on 20/8/15 at 03:25 PM |
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hows it wired up, where is it getting its source from?
Build: http://www.martinsfurybuild.co.uk/
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russtik
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| posted on 20/8/15 at 03:49 PM |
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It's just a simple reed switch, 2 wires (earth + feed from digidash).
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GeoffT
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| posted on 20/8/15 at 04:32 PM |
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Is the reed switch in the correct orientation in relation to the magnet - the magnet should pass the end of the reed, i.e. the short side opposite the
wire, not the longest side. Getting this wrong can cause the speed doubling effect you mention.
The reed switch on my acewell became a bit intermittent, I rather objected to paying the inflated acewell price and used one of
these, worked perfectly....
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russtik
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| posted on 20/8/15 at 04:44 PM |
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This is the type of switch I have, the magnet passes the tip.
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GeoffT
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| posted on 20/8/15 at 04:57 PM |
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That's a different type to the one fitted to my unit which looked just like the one shown in the link. I'm not sure if the two types are
interchangeable.
The issues you mention all sound like a sensor issue though.
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britishtrident
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| posted on 20/8/15 at 05:59 PM |
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Wiring/connection issue would be my first suspect.
Over reading to me indicates a connection making and breaking under vibration or movement. As with ABS sensors tracking this type of fault is a lot
easier with an even a basic oscilloscope.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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russtik
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| posted on 20/8/15 at 06:17 PM |
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quote:
Originally posted by britishtrident
Wiring/connection issue would be my first suspect.
Over reading to me indicates a connection making and breaking under vibration or movement.
Good call, I previously recall a different weak to connection to the dash before so this may be the case for the speedo now. I will investigate...
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ravingfool
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| posted on 20/8/15 at 06:59 PM |
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Let us know how you get on. I've been putting off resolving this issue on my car too (also acewell and same sensor as you)! I've been
prioritising other things but this is now next on my list whenever I get a couple of hours to play with the car.
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pekwah1
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| posted on 21/8/15 at 12:33 PM |
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FYI, speedo worked a treat on the striker before i changed the prop (never got round to mounting it correctly.
Just try and make sure you've got a nice solid bracket for the sensor, and that the magnet is passing very close (within a few mm max) and
again, mine worked a treat! Hope this helps.
Also, there are some interesting settings on the acewell that if you get wrong will give ridiculous readings so worth a good read of the manual
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russbost
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| posted on 22/8/15 at 07:09 AM |
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To do what you describe it pretty much has to be either a connection making & breaking or the sensor itself failing.
I would suggest check all connections in the path between sensor & Acewell, if nothing obvious then with the car stationary & engine off, so
no vibration, remove the sensor & run a magnet back & forth past the tip, this should generate a speed signal which will vary with frequency
depending how quickly you move the magnet back & forth. If the reading is consistent then the sensor is almost certainly ok, if not then probably
sensor fault. Assuming sensor appears ok get someone else to wiggle all the wiring & connections to see if you can simulate the fault, might
point you at the correct bit of wiring to examine/replace.
If it does prove to be a sensor we have them from stock
I no longer run Furore Products or Furore Cars Ltd, but would still highly recommend them for Acewell dashes, projector headlights, dominator
headlights, indicators, mirrors etc, best prices in the UK! Take a look at http://www.furoreproducts.co.uk/ or find more parts on Ebay, user names
furoreltd & furoreproducts, discounts available for LCB users.
Don't forget Stainless Steel Braided brake hoses, made to your exact requirements in any of around 16 colours.
http://shop.ebay.co.uk/furoreproducts/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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ravingfool
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| posted on 24/8/15 at 11:53 AM |
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quote:
Originally posted by pekwah1
FYI, speedo worked a treat on the striker before i changed the prop (never got round to mounting it correctly.
Just try and make sure you've got a nice solid bracket for the sensor, and that the magnet is passing very close (within a few mm max) and
again, mine worked a treat! Hope this helps.
Also, there are some interesting settings on the acewell that if you get wrong will give ridiculous readings so worth a good read of the manual
Yeah I'm not too worried about this in my case but always interested to see what similar problems people are having - helps me rule out or
consider other solutions if it turns out to be more complicated than expected.
Oddly the speedo worked fine for the short time before the magnet made a break for it; then when I plonked a new magnet on I've ended up with an
erratic reading and approximately double what it should be. With the weather being what it has been recently I've just been getting out in the
car whenever the sun shines briefly but haven't had the time to play with the setup.
I know it worked ok before though so hopefully it should just be a case of tinkering with it a bit.
I've got a holiday coming up shortly and then some rather more pressing issues to resolve afterwards so I reckon the car is going to be off the
road until October:
Issue 1. I've been suffering with an air leak which has been causing a high idle at tickover (and getting worse). I fixed a crack in the
manifold but this didn't improve things. On removing the manifold entirely I found one more hairline crack but when showing my girlfriend what
I was up to (she occasionally pretends to be interested to humour me) she pointed out that on the underside of the manifold she could see clear
daylight between one of the trumpets and the airbox!
Issue 2. passenger side engine mount has begun to collapse!
Other than these problems the car drove really nicely on a quick drive on Friday!
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