Fuel guage/sender incompatable
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Tuned
Joined: Jan 2003
Posts: 486
Likes: 66
From: South Carolina
Fuel guage/sender incompatable
I bought a set of antique gold guages from Ford Motorsport for my '55.The fuel guage reads 240 ohms empty and 33 ohms full.
I bought a '65 Mustang fuel tank and sender kit on E-Bay.The sender reads 73 ohms empty and 10 ohms full.
The sending unit that came with the fuel guage won't work in my tank so my question is "can I make these compatable by using a resistor or something"?
I bought a '65 Mustang fuel tank and sender kit on E-Bay.The sender reads 73 ohms empty and 10 ohms full.
The sending unit that came with the fuel guage won't work in my tank so my question is "can I make these compatable by using a resistor or something"?
Post Fiend
Joined: Nov 2002
Posts: 9,987
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From: Memphis, TN
Fuel guage/sender incompatable
Measure the resistance across the gauge (not what it takes to move it, but just between its terminals), double it, and install a 16 Watt (minmum) resistor of that rating across the gauge terminals. That will keep the gauge from pulling too much current with the low-resistance sender, but still show a fairly accurate reading.
My reasoning is that the gauge operates at ~3x the resistance of the sender troughout the whole range, so adding a resistor of double its resistance will pull the other 2/3 of the current around it.
Since the sender alone will flow ~1.2A at 12V on Empty, I chose 16W (1.2A x 12V = 14.4W) as the minimum heat dissipation.
My reasoning is that the gauge operates at ~3x the resistance of the sender troughout the whole range, so adding a resistor of double its resistance will pull the other 2/3 of the current around it.
Since the sender alone will flow ~1.2A at 12V on Empty, I chose 16W (1.2A x 12V = 14.4W) as the minimum heat dissipation.
Last edited by steve83; Jun 26, 2003 at 02:10 PM.
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From: Virginia
Fuel guage/sender incompatable
I don't think it will work. The new guage requires 240 ohms to show empty(I would think you would want it most accurate near empty). If the sender has 73 ohms at empty you need a resistor 240-73=167 ohms. When the tank is full you would have 10 ohms + the 167 ohms=177 ohms. This would probably show about 1/4 tank on the new gauge.
Putting any resistance in parallel will just lower the resistance you have already, making it impossible to get the required 240 ohms.
Is there any way you can make an adapter plate to mount the correct sending unit in the mustang tank? Or if you where brave enough, could you mix and match the sending unit parts and floats to get the right resistance value for the guage? The mustang is a very popular car, so I wouldn't be surprised if a company made an aftermarket sending unit for it.
Putting any resistance in parallel will just lower the resistance you have already, making it impossible to get the required 240 ohms.
Is there any way you can make an adapter plate to mount the correct sending unit in the mustang tank? Or if you where brave enough, could you mix and match the sending unit parts and floats to get the right resistance value for the guage? The mustang is a very popular car, so I wouldn't be surprised if a company made an aftermarket sending unit for it.
Thread Starter
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Tuned
Joined: Jan 2003
Posts: 486
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From: South Carolina
Fuel guage/sender incompatable
I was thinking about adapting the electrical portion of the correct ohm sender to the sender that fits the tank,but it seems to take a lot of pressure to raise and lower the float.
The correct ohm sender seems to have been made for a long,deep tank.Its got a lot of travel, and a long,but adjustable float arm.
I called Motorsport tech line today but, he told me to call Autometer,the actual maker of the guage.I haven't called them yet.
The correct ohm sender seems to have been made for a long,deep tank.Its got a lot of travel, and a long,but adjustable float arm.
I called Motorsport tech line today but, he told me to call Autometer,the actual maker of the guage.I haven't called them yet.
Posting Guru
Joined: Nov 2002
Posts: 2,440
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From: Ventura County, CA
Fuel guage/sender incompatable
United Speedometer Service rectified my sending unit problem with my VDO gauges for a very reasonable price. Maybe they can help you, too. They're in Riverside, CA @ (909) 684-0292. Ask for Vane or Jason.
Daryl
Daryl
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Tuned
Joined: Jan 2003
Posts: 486
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From: South Carolina
Fuel guage/sender incompatable
Thanks for steering me in the right direction,guys.
I now realize that there are no shortcuts.I got a price from the folks at United Speedometer Service to re-do my sender,but then I found out that Autometer makes just what I need (10-73 ohm guage) for about a third the price,so I ordered a new guage.
I now realize that there are no shortcuts.I got a price from the folks at United Speedometer Service to re-do my sender,but then I found out that Autometer makes just what I need (10-73 ohm guage) for about a third the price,so I ordered a new guage.
