Fuel level

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BiKenG
Posts: 53
Joined: Tue Feb 10, 2015 12:08 pm
Location: Surrey, UK

Fuel level

Postby BiKenG » Mon Jul 06, 2015 6:52 pm

According to the bike's workshop manual, the fuel sender I am using should read:-

Full = 12-14 kΩ
Empty = 119-121 kΩ

So I used a 10k resistor, as suggested by RT's chart. But that gave me an empty voltage reading of 54 mV, dropping to about 20 mV at approx. 2/3rds full. This would indicate that the value of the resistor is way too high. Can anyone suggest what is wrong here - apart from the obvious that Honda's figures for sender resistance values must be hopelessly wrong?
You can't have too many bikes

Support
Posts: 300
Joined: Mon Nov 21, 2005 4:09 pm

Postby Support » Tue Jul 07, 2015 4:00 pm

Hi There,

I would suggest that rather than Kohms, the sensor is actually outputting ohms. This is much more common on road vehicles.

With this in mind, the 10K pullup you have added will indeed be much too large. I would recommend a pull up resistor that is close to the maximum resistance achieved by the sender, also taking into account the current draw if using the dash's built in 5v reference.

If for example you were to use a 120ohm pullup, you would be quite close to the maximum current draw from the dash when the tank is full, so possibly something such as a 180ohm - 200ohm resistor would give best resolution whilst remaining a safe current draw.

Kind Regards,
RT Support (SK)
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BiKenG
Posts: 53
Joined: Tue Feb 10, 2015 12:08 pm
Location: Surrey, UK

Postby BiKenG » Tue Jul 07, 2015 6:47 pm

The D2P has 2 x 5V ref. lines, each apparently capable of 500mA, according to the specs. So I should be ok even if the fuel sender is such low resistance. Or are the specs wrong?

I'm still puzzled though as to how Honda could have managed to state sensor specs 1000 times wrong.

Having said that, I think the air temp sensor is way higher than the ~5Ω stated in the manual, but I've got no reading at all on the D2P for that so I may have simply configured it wrong.

I guess measure them is the final answer on that.
You can't have too many bikes

BiKenG
Posts: 53
Joined: Tue Feb 10, 2015 12:08 pm
Location: Surrey, UK

Postby BiKenG » Sun Aug 09, 2015 9:39 am

I have since had the tank off and measured the fuel level sender's resistance when empty and full (actually, tank upside down :-) ) and indeed the manual has incorrectly used kΩ when it should have been Ω. That is the actual official Honda workshop manual. Unlike Honda to make such a gaff.

I'll change the resistor and try again.
You can't have too many bikes


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