Home » Public Forums » GMCnet » [GMCnet] GMC Fuel Tank Sensor resistance
| [GMCnet] GMC Fuel Tank Sensor resistance [message #99910] |
Wed, 15 September 2010 12:48  |
kelvin
Messages: 608
Registered: February 2004
Location: Eugene, OR
Karma: 0
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Need to know what the resistance does related to fuel level. This is
what I've found at one online site.
Accurate? Wrong?
Thanks in advance,
Kelvin
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/With General Motors analog resistance fuel gauges, the basic operating
principle is the same but electrically opposite. Resistance in the
sending unit decreases as the fuel level drops, and increases and the
level goes up. When the tank is empty, the sending unit reads about zero
ohms, and when the tank is full it reads about 90 ohms. Gauge operation
is also the same with maximum needle deflection corresponding to minimum
resistance in the sending unit. In this case, maximum deflection is
required to move the needle all the way over to the empty mark./
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| Re: [GMCnet] GMC Fuel Tank Sensor resistance [message #99914 is a reply to message #99910] |
Wed, 15 September 2010 13:30  |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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""Need to know what the resistance does related to fuel level. This is
what I've found at one online site.
Accurate? Wrong?
Thanks in advance,
Kelvin
"" Yes, that article is correct--90 ohms means full and 0 is empty
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] GMC Fuel Tank Sensor resistance [message #99915 is a reply to message #99910] |
Wed, 15 September 2010 13:34 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Kelvin, you got me curious so I got my manual out and checked the schematic
which is on page 12-12 in the x-7525 GMC manual. It shows high resistance
with an empty tank, and low resistance with a full tank. There is NOT 12
volts in the sender circuit. Do not check it with full battery voltage or
you will probably burn out the resistance wire in the sender. About the only
fix for the senders is replacement. Again, sorry for the confusing
information.
Jim Hupy
Salem, Or
78 Royale 403
On Wed, Sep 15, 2010 at 10:48 AM, Kelvin Dietz <kelvin@datsuns.com> wrote:
> Need to know what the resistance does related to fuel level. This is
> what I've found at one online site.
> Accurate? Wrong?
>
>
> Thanks in advance,
> Kelvin
>
>
>
> ---------------------------------------------------------------------------------
>
> /With General Motors analog resistance fuel gauges, the basic operating
> principle is the same but electrically opposite. Resistance in the
> sending unit decreases as the fuel level drops, and increases and the
> level goes up. When the tank is empty, the sending unit reads about zero
> ohms, and when the tank is full it reads about 90 ohms. Gauge operation
> is also the same with maximum needle deflection corresponding to minimum
> resistance in the sending unit. In this case, maximum deflection is
> required to move the needle all the way over to the empty mark./
>
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
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| Re: [GMCnet] GMC Fuel Tank Sensor resistance [message #99919 is a reply to message #99915] |
Wed, 15 September 2010 13:45 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Geez Kelvin, I did it again. Forty lashes at least. What Bob said is
correct. The schematic is confusing but agrees with him. I forgot about the
float arm belcrank changing the range of motion. up is down and down is up
at least in this case.
Jim Hupy
Salem, Or
78 Royale 403
On Wed, Sep 15, 2010 at 11:34 AM, James Hupy <jamesh1296@gmail.com> wrote:
> Kelvin, you got me curious so I got my manual out and checked the schematic
> which is on page 12-12 in the x-7525 GMC manual. It shows high resistance
> with an empty tank, and low resistance with a full tank. There is NOT 12
> volts in the sender circuit. Do not check it with full battery voltage or
> you will probably burn out the resistance wire in the sender. About the only
> fix for the senders is replacement. Again, sorry for the confusing
> information.
> Jim Hupy
> Salem, Or
> 78 Royale 403
>
> On Wed, Sep 15, 2010 at 10:48 AM, Kelvin Dietz <kelvin@datsuns.com>wrote:
>
>> Need to know what the resistance does related to fuel level. This is
>> what I've found at one online site.
>> Accurate? Wrong?
>>
>>
>> Thanks in advance,
>> Kelvin
>>
>>
>>
>> ---------------------------------------------------------------------------------
>>
>> /With General Motors analog resistance fuel gauges, the basic operating
>> principle is the same but electrically opposite. Resistance in the
>> sending unit decreases as the fuel level drops, and increases and the
>> level goes up. When the tank is empty, the sending unit reads about zero
>> ohms, and when the tank is full it reads about 90 ohms. Gauge operation
>> is also the same with maximum needle deflection corresponding to minimum
>> resistance in the sending unit. In this case, maximum deflection is
>> required to move the needle all the way over to the empty mark./
>>
>> _______________________________________________
>> GMCnet mailing list
>> List Information and Subscription Options:
>> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>>
>
>
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| Re: [GMCnet] GMC Fuel Tank Sensor resistance [message #99920 is a reply to message #99919] |
Wed, 15 September 2010 13:53 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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Senior Member |
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""Geez Kelvin, I did it again. Forty lashes at least. What Bob said is
correct. The schematic is confusing but agrees with him. I forgot about the
float arm belcrank changing the range of motion. up is down and down is up
at least in this case.
Jim Hupy
Salem, Or
78 Royale 403
""
I wonder what Rob Mueller would have said 
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] GMC Fuel Tank Sensor resistance [message #99921 is a reply to message #99910] |
Wed, 15 September 2010 13:52 |
tmaki
Messages: 200
Registered: September 2005
Karma: 0
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On 9/15/2010 10:48 AM, Kelvin Dietz wrote:
> Need to know what the resistance does related to fuel level. This is
> what I've found at one online site.
> Accurate? Wrong?
Accurate.
Be careful, though, if you're depending on "0" = 0 and "90"
= 90. Those are general design specifications and in
practical terms, you'll be bouncing off padded walls trying
to figure out why you can't get 0 and 90 on your meter.
Although yours might be spot on.
When I had mine apart, I measured them and found they were
way off (I posted the readings months ago.). The senders are
nominally a 90-degree arc, but read nowhere near a
linear/angular relationship, although yours might be spot
on. I measured mine in terms of angle hoping to find by some
chance that there was a direct relationship between angle
and resistance. Not even close. Although yours might be spot on.
Also, the wiper contact travels along the inside of the arc
of resistance wire wound around a curved slice of insulating
cardboard-like material. That curved element gets warped
after time, and the wiper contact element may get skewed off
the resistance wire, making sporadic contact, and after a
bunch of cycles may just skitter off the edge, or the
insulator warps so much that it breaks the hair-fine wire.
Although yours might be spot on.
Toby Maki
'73 Glacier 230
Riverside, CA
>
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| Re: [GMCnet] GMC Fuel Tank Sensor resistance [message #99931 is a reply to message #99924] |
Wed, 15 September 2010 14:23 |
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WD0AFQ
Messages: 7111
Registered: November 2004
Location: Dexter, Mo.
Karma: 207
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Kelvin, when I rebuild one I check for 90, 45, and 0.
Dan
3 In Stainless Exhaust Headers
One Ton All Discs/Reaction Arm
355 FD/Quad Bag/Alum Radiator Manny Tran/New eng.
Holley EFI/10 Tire Air Monitoring System
Solarized Coach/Upgraded Windows
Satelite TV/On Demand Hot Water/3Way Refer
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