Can someone please tell me what the full and empty readings for for the fuel sending unit.
Ohm reading and voltage if possible please. Fitting a dash 2 and want to compare to the standard reading
[Mk2] [Turbo] ohm/voltage reading of fuel sending unit full and empty.
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Re: [Mk2] [Turbo] ohm/voltage reading of fuel sending unit full and empty.
The fuel level sender should give you the following readings measured at the connector after disconnection:
Raised (full tank) around 3 ohms
Lowered (empty tank) around 110 Ohms
When I last changed mine I also connected the sender up outside of the fuel tank with the float arm in both positions to check the meter was reading correctly. But if you do that, don't forget the needle on the fuel gauge takes some time to travel to the correct position.
Don't forget to keep the car well ventilated when changing the sensor.
Paul
Raised (full tank) around 3 ohms
Lowered (empty tank) around 110 Ohms
When I last changed mine I also connected the sender up outside of the fuel tank with the float arm in both positions to check the meter was reading correctly. But if you do that, don't forget the needle on the fuel gauge takes some time to travel to the correct position.
Don't forget to keep the car well ventilated when changing the sensor.
Paul
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- Joined: Fri Apr 29, 2016 10:33 pm
Re: [Mk2] [Turbo] ohm/voltage reading of fuel sending unit full and empty.
Pauln wrote:The fuel level sender should give you the following readings measured at the connector after disconnection:
Raised (full tank) around 3 ohms
Lowered (empty tank) around 110 Ohms
When I last changed mine I also connected the sender up outside of the fuel tank with the float arm in both positions to check the meter was reading correctly. But if you do that, don't forget the needle on the fuel gauge takes some time to travel to the correct position.
Don't forget to keep the car well ventilated when changing the sensor.
Paul
Thanks.
I'm struggling with converting it to a volt reading from ohm. The dash2 analogue wire for the sender is 5v.
Would I be right in assuming it's
0.63v full tank 55litres
4.3v empty
?
I'm going insane
Re: [Mk2] [Turbo] ohm/voltage reading of fuel sending unit full and empty.
I'm afraid I've no experience of connecting this up to something like the dash 2, but you do need to remember there are two parts to the MR2 fuel sender.
You have the float arm that operates a wire wound variable resistor arm to provide the correct resistance to be interpreted by the std fuel gauge, and you also have the low level fuel sensor that operates the warning light on the std dash.
So you will need to identify the correct wires for the fuel level arm.
Hopefully someone with experience of the Dash2 can help, but looking at the instructions available on line the setup procedure does look a bit more involved than a conversion from resistance to voltage. V= IR is all well and good but it depends on how the dash operates:
Link
Good luck.
Paul
You have the float arm that operates a wire wound variable resistor arm to provide the correct resistance to be interpreted by the std fuel gauge, and you also have the low level fuel sensor that operates the warning light on the std dash.
So you will need to identify the correct wires for the fuel level arm.
Hopefully someone with experience of the Dash2 can help, but looking at the instructions available on line the setup procedure does look a bit more involved than a conversion from resistance to voltage. V= IR is all well and good but it depends on how the dash operates:
Link
Good luck.
Paul
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Re: [Mk2] [Turbo] ohm/voltage reading of fuel sending unit full and empty.
I believe the low level light is separate. I need to figure out the resistance ohm. Convert it to a volt reading so the float up top and bottom we know the ohm reading. I just need to know what the 110ohm in the volt reading will be
Re: [Mk2] [Turbo] ohm/voltage reading of fuel sending unit full and empty.
Well assuming you're running new cables in to run this on the 5v supply from your dash2, and assuming this is +5v, I guess if you could just connect the +5v to the sender, and you should in theory then be able to use a meter to measure the voltage returned between the other side of the sender and ground, with the float is in the up and down positions. If you don't connect the return feed from the sender to the dash that should be isolated, so the only thing to be careful of is that you don't exceed the current limit of the 5v supply.
But as I said, I really don't know anything about Dash2 so I could be wrong. The link I looked at seemed to suggest you might need an additional load resistor in the circuit to make it work correctly when you finally hook it up. Which is why I was hoping someone who knew more about setting this up could advise you, as there's always a risk of causing damage to the electronics if it's connected incorrectly.
Paul
But as I said, I really don't know anything about Dash2 so I could be wrong. The link I looked at seemed to suggest you might need an additional load resistor in the circuit to make it work correctly when you finally hook it up. Which is why I was hoping someone who knew more about setting this up could advise you, as there's always a risk of causing damage to the electronics if it's connected incorrectly.
Paul
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Re: [Mk2] [Turbo] ohm/voltage reading of fuel sending unit full and empty.
I do appreciate your help.
I am getting readings up on the display. I set to display from 55 to zero.
I'm just not getting accurate readings.
I am getting readings up on the display. I set to display from 55 to zero.
I'm just not getting accurate readings.
Re: [Mk2] [Turbo] ohm/voltage reading of fuel sending unit full and empty.
The reason your readings are not accurate is because as it stands the voltage drop across your fuel tank sender (variable resistor) will be 5 volts (if you're using the Dash 2 reference voltage) regardless, it is the only resistor in the circuit so all that changes with fuel level is the current flowing through it.
On that note if you have simply wired it up like so:
Dash 2 5V reference > fuel tank sender > Dash 2 analogue input
it might be advisable to disconnect it, according to their website the maximum current flow on the reference output is 50mA, @3 Ohms (full tank) you will be pulling 1.67A!
https://www.race-technology.com/wiki/in ... FuelSender
You need to add an additional resistor as Pauln mentioned (2 wire sender)
https://www.race-technology.com/wiki/in ... ensorToDL1
this way as the resistance varies on the fuel sender so does the total circuit resistance, in turn the current flowing through the circuit will change and the volt drop across the added resistor will scale accordingly.
Not wanting to teach you to suck eggs but here is the math based on the above link recommendation of adding a 1k ohm and using Paul's values of 3 Ohm (full) and 110 ohm (empty)
V=IR
5=I*1003 (total circuit resistance for a full tank)
5/1003=0.0045A
0.0045*1000= 4.5V this will be the analogue input voltage on a full tank
5=I*1110 (empty tank)
5/1110=0.004985
0.004985*1000= 4.985V voltage for an empty tank
Edit: Just corrected the maths as calculated the volt drop across the sender itself and not the 1K load resistor!
On that note if you have simply wired it up like so:
Dash 2 5V reference > fuel tank sender > Dash 2 analogue input
it might be advisable to disconnect it, according to their website the maximum current flow on the reference output is 50mA, @3 Ohms (full tank) you will be pulling 1.67A!
https://www.race-technology.com/wiki/in ... FuelSender
You need to add an additional resistor as Pauln mentioned (2 wire sender)
https://www.race-technology.com/wiki/in ... ensorToDL1
this way as the resistance varies on the fuel sender so does the total circuit resistance, in turn the current flowing through the circuit will change and the volt drop across the added resistor will scale accordingly.
Not wanting to teach you to suck eggs but here is the math based on the above link recommendation of adding a 1k ohm and using Paul's values of 3 Ohm (full) and 110 ohm (empty)
V=IR
5=I*1003 (total circuit resistance for a full tank)
5/1003=0.0045A
0.0045*1000= 4.5V this will be the analogue input voltage on a full tank
5=I*1110 (empty tank)
5/1110=0.004985
0.004985*1000= 4.985V voltage for an empty tank
Edit: Just corrected the maths as calculated the volt drop across the sender itself and not the 1K load resistor!