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jvds30(at)hotmail.com
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 Posted: Mon Jul 24, 2006 12:52 pm Post subject: Fuel indicator probs |
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Hello all,
For the third time in a row (within a year) my fuel indicator went US.
It's the right tank indicator which drops to 12 liters, even when the tank is full.
If the indicator is replaced, it works fine for a couple of months, than it stops.. Must be something electrical...
Anyone of you familiar with the problem?
Best regards,
Jerome Van Der Schaar
www.yakkes.com
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Rob Rowe
Joined: 10 Jan 2006
Posts: 124
Location: Berkshire, UK
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| Posted: Tue Jul 25, 2006 3:35 am Post subject: Re: Fuel indicator probs |
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Jerome,
FWIW I can only offer the following from theory ... I've not had hands on experience of this problem.
The fuel level sensing is clever, but relatively complex ... each fuel sender has a 10Khz square wave primary signal induced into four embedded secondary parallel coils (each with a different winding).
On the outside of the fuel sender is a floating inductor that creates a unique combination of "phases" in the four secondary coils depending on the fuel level.
The display unit then decodes the unique phase combinations into a specific fuel bar light ... no electrical moving parts to wear out or spark, no calibration required, accurate to +/- 5mm of fuel tank level under normal operating conditions.
Back to your problem ... presume the display units you've replaced have been positively tested as being faulty i.e connections swapped over with the left tank sender?
If they are all damaged then this is going to be a mare to fault find as any external influence i.e. DC supply voltage spikes, is common to both left / right tanks systems, that are identical but independent ... so would likely damage both units not just one.
So possibly the wiring between the sender & display has been damaged and is intermittently shorting ... but would not expect this to permanently damage the display unit, just give a wrong reading.
Probably worth you checking the connections at both ends of the cable (not sure how you access the fuel sender though) - there are 7 wires ... earth + 4 secondary coil outputs + 2 primary coil inputs.
I'm not sure of the following as I can only infer the connections from the schematic ...
Sender - Pins 9 / 10 primary winding, Pins 1 - 5 (4 off) secondary winding & earth
Display - Pins 1 / 2 primary winding, Pins 3 - 7 (4 off) secondary winding & earth
There are also intermediate canon plugs located at "Station 4 outside" labelled "1-20" for left tank & "1-21" for the right tank.
I've attached a high level schematic of the above ... note there is an error in that the primary coils are shown as having a common earth, in fact they have a dedicated return line to the 10Khz generator (as per the pin description).
Hope this helps!
Cheers, Rob
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| Description: |
| YAK-52 Fuel Display Schematic |
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Download |
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YAK-52 Fuel Display.pdf |
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76.93 KB |
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436 Time(s) |
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jvds30(at)hotmail.com
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| Posted: Tue Jul 25, 2006 3:54 am Post subject: Fuel indicator probs |
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Hi Rob,
Thanks for your rapid response.
<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />
It must be external electrical like you figured, if we switch the plugs on the indicator, still the right one stays on the <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" />12 liters.
This indicator is the second NEW one, so it can't be any coincidence anymore.
I will start checking the connectors like you figured, thank you for the attachment, appreciate it.
Best regards
Jerome
> To: yak-list(at)matronics.com
| Quote: | From: yak-list(at)robrowe.plus.com
Date: Tue, 25 Jul 2006 04:36:01 -0700
Subject: Re: Fuel indicator probs
--> Yak-List message posted by: "Rob Rowe" <yak-list(at)robrowe.plus.com>
Jerome,
FWIW I can only offer the following from theory ... I've not had hands on experience of this problem.
The fuel level sensing is clever, but relatively complex ... each fuel sender has a 10Khz square wave primary signal induced into four embedded secondary parallel coils (each with a different winding).
On the outside of the fuel sender is a floating inductor that creates a unique combination of "phases" in the four secondary coils depending on the fuel level.
The display unit then decodes the unique phase combinations into a specific fuel bar light ... no electrical moving parts to wear out or spark, no calibration required, accurate to +/- 5mm of fuel tank level under normal operating conditions.
Back to your problem ... presume the display units you've replaced have been positively tested as being faulty i.e connections swapped over with the left tank sender?
If they are all damaged then this is going to be a mare to fault find as any external influence i.e. DC supply voltage spikes, is common to both left / right tanks systems, that are identical but independent ... so would likely damage both units not just one.
So possibly the wiring between the sender & display has been damaged and is intermittently shorting ... but would not expect this to permanently damage the display unit, just give a wrong reading.
Probably worth you checking the connections at both ends of the cable (not sure how you access the fuel sender though) - there are 7 wires ... earth + 4 secondary coil outputs + 2 primary coil inputs.
I'm not sure of the following as I can only infer the connections from the schematic ...
Sender - Pins 9 / 10 primary winding, Pins 1 - 5 (4 off) secondary winding & earth
Display - Pins 1 / 2 primary winding, Pins 3 - 7 (4 off) secondary winding & earth
There are also intermediate canon plugs located at "Station 4 outside" labelled "1-20" for left tank & "1-21" for the right tank.
I've attached a high level schematic of the above ... note there is an error in that the primary coils are shown as having a common earth, in fact they have a dedicated return line to the 10Khz generator (as per the pin description).
Hope this helps!
Cheers, Rob
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=49707#49707
Attachments:
http://forums.matronics.com//files/yak_52_fuel_display_285.pdf
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rkent(at)wlacrussianeng.c
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| Posted: Tue Jul 25, 2006 4:53 am Post subject: Fuel indicator probs |
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Jerome, Rob,
The only way to access the fuel sender itself is to drop the tank as there
is no access hole in the top surface of the wing. The sender is approx 1ft
inboard from the filler.
Regards
Rob Kent
Stores Manager
WLAC - Russian Engineering
www.wlacrussianeng.co.uk
Tel: +44 1628 829 165
Mob: +44 7866 438 293
Fax: +44 1628 828 961
---
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viperdoc(at)mindspring.co
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| Posted: Tue Jul 25, 2006 12:15 pm Post subject: Fuel indicator probs |
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Rob,
Question concerning the fuel indicator on the 50. The fuel totalizer on my
50 went TU and was replaced with a 52 indicator. It only reads accurate
when it gets down to 40 liters. When you drain the tank (s) (Aux and main),
it has approx 65 liters (between the two). Is there a way to fit a second
sending unit in the Aux tank to couple to the unused right side of the fuel
gauge. The main tank is connected to the left side of the fuel gauge and
the right side is blank.
Doc Kemp
| Quote: | [Original Message]
From: Rob Kent <rkent(at)wlacrussianeng.co.uk>
To: <yak-list(at)matronics.com>
Date: 7/25/2006 8:30:16 AM
Subject: Re: Re: Fuel indicator probs
Jerome, Rob,
The only way to access the fuel sender itself is to drop the tank as
there
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| Quote: | is no access hole in the top surface of the wing. The sender is approx
1ft
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[quote] inboard from the filler.
Regards
Rob Kent
Stores Manager
WLAC - Russian Engineering
www.wlacrussianeng.co.uk
Tel: +44 1628 829 165
Mob: +44 7866 438 293
Fax: +44 1628 828 961
---
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Rob Rowe
Joined: 10 Jan 2006
Posts: 124
Location: Berkshire, UK
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| Posted: Wed Jul 26, 2006 6:45 am Post subject: Re: Fuel indicator probs |
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Doc.
Spoke with Rob Kent & we reckon you'll not be any better off trying to use the "other" side of the Yak-52 gauge for your aux tank - as both the sender (specific to the fuel tank dimensions) & the display (decoding the phase combinations of a given sender) need to be matched for this to read accurately.
Cheers, Rob R
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viperdoc(at)mindspring.co
Guest
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| Posted: Wed Jul 26, 2006 10:33 am Post subject: Fuel indicator probs |
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Rob,
Thanks, I was afraid of that. I will be better off using a Shadin fuel flow
monitor than fooling with the Fuel gauge. Appreciate the input.
Doc
| Quote: | [Original Message]
From: Rob Rowe <yak-list(at)robrowe.plus.com>
To: <yak-list(at)matronics.com>
Date: 7/26/2006 9:56:48 AM
Subject: Re: Fuel indicator probs
Doc.
Spoke with Rob Kent & we reckon you'll not be any better off trying to
use the "other" side of the Yak-52 gauge for your aux tank - as both the
|
sender (specific to the fuel tank dimensions) & the display (decoding the
phase combinations of a given sender) need to be matched for this to read
accurately.
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