I need help from an electronics genius.
Thread Starter
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Road Captain
Joined: Jul 2015
Posts: 694
Likes: 50
From: Billings, Montana Out in the Wild West.
I need help from an electronics genius.
I am looking at getting some different gauges for my 08 Ultra and the question I have concerns the fuel gauge. The ohm readings I get the fuel level sender on my bike is 251.5 - 39.8 I found the following gauge I'm interested in but it's compatible with the following ohm ranges of senders. http://prosportgauges.com/evo-electr...vel-gauge.aspx
0-30
0-90
0-120
73-10
10-180
16-158
107.5-7
131-12
240-33
What I'm wondering is if there are any electrical geniuses out there who could tell me if resisters could be added to my fuel level sending unit that would make it compatible with this gauge, and if so what resister would I need ? P.S. I also posted this question in the Electrical section of this forum but it doesn't seem to get the same amount of traffic as the Touring section which is why I posted it here also.
0-30
0-90
0-120
73-10
10-180
16-158
107.5-7
131-12
240-33
What I'm wondering is if there are any electrical geniuses out there who could tell me if resisters could be added to my fuel level sending unit that would make it compatible with this gauge, and if so what resister would I need ? P.S. I also posted this question in the Electrical section of this forum but it doesn't seem to get the same amount of traffic as the Touring section which is why I posted it here also.
Last edited by madsonp; Jan 27, 2016 at 12:13 PM. Reason: Added P.S.
Don't know what meter you are using to measure your bike but you're only off by a few ohms from what their gauge will accept. You could have a little added resistance in your meter leads or your meter could be off by a few ohms. I think their gauge will work for you. I would send them an email with your measurements and see what they say.
Club Member
Joined: Sep 2010
Posts: 1,689
Likes: 457
Don't know what meter you are using to measure your bike but you're only off by a few ohms from what their gauge will accept. You could have a little added resistance in your meter leads or your meter could be off by a few ohms. I think their gauge will work for you. I would send them an email with your measurements and see what they say.
Thread Starter
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Road Captain
Joined: Jul 2015
Posts: 694
Likes: 50
From: Billings, Montana Out in the Wild West.
Thanks for the replies guys, I did send them an e-mail basically asking the same question, their reply was as follows: "I'm sorry but the closest setting we have is 240-33, I'm not sure if that would work for your application".
Lets say if my meter was reading correctly, I wonder if that small of a deference in ohm's would be noticeable enough on the gauge itself? I might just spend the $72 and get one to see what it does. I guess if it doesn't work, I could always sell it on ebay.
Lets say if my meter was reading correctly, I wonder if that small of a deference in ohm's would be noticeable enough on the gauge itself? I might just spend the $72 and get one to see what it does. I guess if it doesn't work, I could always sell it on ebay.
Tourer
Joined: Apr 2012
Posts: 482
Likes: 30
From: Michigan/Florida
They are telling you the swing in resistance that'll happen from full to empty. If 33 ohms is "empty" on their gauge, adding 10 ohms in series will result in it showing a little more gas in the tank than you actually have - you know, like a stock HD gauge...
Grand HDF Member
Joined: Aug 2014
Posts: 3,609
Likes: 1,601
From: Eastern Ohio
OP, you could run it the way it is. Worst case scenario, if the high number is full and low number is empty, it'll read full longer and won't reach completely empty on the gauge. If you want to do the math, you might find a resistor value that when hooked in parallel would bring the overall impedance down. The problem is, it will do this as a ratio to the total resistance.
This site has an online calculator.
Using that calculator, you would need a 5.5k ohm resistor in parallel with the sending unit to make the 251 come down to 240. But that would barely reduce the 39.8 below 39.5 ohm. To make the low side 39.8 come down to the 33 ohms you're after you'd need a 193 ohm resistor. This will have a much larger effect on your high end resistance, it would drop to 109 ohms. If I were you, I'd try it the way it is, the difference is minimal. It can't be any worse than the gauge that came with the bike from the factory.
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Thread Starter
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Road Captain
Joined: Jul 2015
Posts: 694
Likes: 50
From: Billings, Montana Out in the Wild West.
Well, I just went ahead and ordered one to see if it'll work. If it does it's my intention to also order their Oil Pressure, Volts, and Oil Temperature gauges to replace all my small gauges. I'd put the Oil Temperature gauge in place of the Air Temp. gauge which many here agree is worthless. http://prosportgauges.com/evo-series-Red-and-Blue.aspx Thanks for all the replies guys.
Last edited by madsonp; Jan 27, 2016 at 06:31 PM.
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Road Warrior
Joined: Jun 2014
Posts: 1,357
Likes: 91
From: Michigan
You should be fine according to the HD fuel level circuit there is some variability regarding ohms from the sending unit.
This is from the HD installation manual
Full: 39.5-27.5 ohms
1/2 full: 118.0-97.0 ohms
Empty: 260.0-240 ohms
http://www.harley-davidson.com/en_US...ts/-J02081.pdf.
There may be a bit of accuracy effected by the differential, a 5.5K ohm resistor in parallel from ground to the gauge terminal will bring the empty very close to accurate for your sending unit resistance reading, but doesn't do much for the full side, but honestly I wouldn't worry about the difference.
This is from the HD installation manual
Full: 39.5-27.5 ohms
1/2 full: 118.0-97.0 ohms
Empty: 260.0-240 ohms
http://www.harley-davidson.com/en_US...ts/-J02081.pdf.
There may be a bit of accuracy effected by the differential, a 5.5K ohm resistor in parallel from ground to the gauge terminal will bring the empty very close to accurate for your sending unit resistance reading, but doesn't do much for the full side, but honestly I wouldn't worry about the difference.
Last edited by HardRider1; Jan 27, 2016 at 06:49 PM.
Thread Starter
|
Road Captain
Joined: Jul 2015
Posts: 694
Likes: 50
From: Billings, Montana Out in the Wild West.
You should be fine according to the HD fuel level circuit there is some variability regarding ohms from the sending unit.
This is from the HD installation manual
Full: 39.5-27.5 ohms
1/2 full: 118.0-97.0 ohms
Empty: 260.0-240 ohms
www.harley-davidson.com/en_US/.../-J02081.pdf
There may be a bit of accuracy effected by the differential, a 400 ohm resistor in series from ground to the gauge terminal will bring the empty very close to accurate for your sending unit resistance reading, but doesn't do much for the full side, but honestly I wouldn't worry about the difference.
This is from the HD installation manual
Full: 39.5-27.5 ohms
1/2 full: 118.0-97.0 ohms
Empty: 260.0-240 ohms
www.harley-davidson.com/en_US/.../-J02081.pdf
There may be a bit of accuracy effected by the differential, a 400 ohm resistor in series from ground to the gauge terminal will bring the empty very close to accurate for your sending unit resistance reading, but doesn't do much for the full side, but honestly I wouldn't worry about the difference.