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Canadian Poncho Homepage -> Canadian Poncho -> General Beaumont Discussion -> Fuel gauge reading wrong....
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seventy2plus2


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RE: Fuel gauge reading wrong....
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LT1Caddy wrote:
seventy2plus2 wrote:

When you have the sending unit disconnected, what is the resistance (in Ohms) from the sending unit wire to ground? Considering you seem to figure the tank is about half full, the resistance reading of the sending unit will tell us something.

54.4 OHMS sender wire to ground



On my 70, when I fill the tank, it reads WAY past full. It's been like that on every car I have ever had.

 

I just saw your reply of 54.4 ohms embedded in my note.   Tomorrow I will grab a sending unit from my garage and measure it both full & empty.   If I recall, one reading should be 90 ohms, the other 0 ohms.  I just can't remember which is which.



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LT1Caddy


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seventy2plus2 wrote:
LT1Caddy wrote:
seventy2plus2 wrote:

When you have the sending unit disconnected, what is the resistance (in Ohms) from the sending unit wire to ground? Considering you seem to figure the tank is about half full, the resistance reading of the sending unit will tell us something.

54.4 OHMS sender wire to ground



On my 70, when I fill the tank, it reads WAY past full. It's been like that on every car I have ever had.

 "0" for empty, "90" for full

I just saw your reply of 54.4 ohms embedded in my note.   Tomorrow I will grab a sending unit from my garage and measure it both full & empty.   If I recall, one reading should be 90 ohms, the other 0 ohms.  I just can't remember which is which.

 



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seventy2plus2


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I grabbed a new replacement sending unit from my shelf, it's a Spectra Premium unit. 0 ohms on empty, 140 ohms full (I thought it was supposed to be 90 oms). So, I think your sending unit is working fine, there's a problem with your gauge. There's a resistor across the posts of the gauge, it limits the current going into the tank. Maybe the resistor is missing.

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70 2+2 convertible
70 2+2 hardtop
70 Parisienne hardtop

 

 
LT1Caddy


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seventy2plus2 wrote:

I grabbed a new replacement sending unit from my shelf, it's a Spectra Premium unit. 0 ohms on empty, 140 ohms full (I thought it was supposed to be 90 oms). So, I think your sending unit is working fine, there's a problem with your gauge. There's a resistor across the posts of the gauge, it limits the current going into the tank. Maybe the resistor is missing.

 

Hi... Pretty sure it's 90 Ohms for FULL. Checked numerous websites and you are the first person to say that FULL reads 140 ohms. I've been thinking the last week it's the gauge, just haven't got my body tuned to lay on the floor (I'm 6'4" with a bad back) to check the readings on the fuel gauge....

I have a spare cluster I will check for resistor.... 

THX



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4SPEED427


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As I was reading this I just remembered I have a new (reproduction) 66 Pontiac tank sender. I'm not sure that it's the same as Biscayne though. Would you like me to test it?

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1966 Grande Parisienne, 396 1 of 23 factory air cars (now converted to a "factory" 4 speed)
LT1Caddy


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Yes please Carl. Do you know the make?

 

THX



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4SPEED427


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It's a Spectra FG88D. Their website says the correct sender for your's is FG88B. It does say 0-95 ohms though and when I measured mine it was about 5-94 ohms, so I'm betting that part of the unit is the same between our cars. 



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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles 

1966 Grande Parisienne, 396 1 of 23 factory air cars (now converted to a "factory" 4 speed)
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4SPEED427


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I'm looking around and it looks like I have the wrong one for my car. It looks like it's for station wagon, although that won't affect the electrical part of it. I'm just glad I never tried to install it!


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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles 

1966 Grande Parisienne, 396 1 of 23 factory air cars (now converted to a "factory" 4 speed)
seventy2plus2


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LT1Caddy wrote:
seventy2plus2 wrote:

I grabbed a new replacement sending unit from my shelf, it's a Spectra Premium unit. 0 ohms on empty, 140 ohms full (I thought it was supposed to be 90 oms). So, I think your sending unit is working fine, there's a problem with your gauge. There's a resistor across the posts of the gauge, it limits the current going into the tank. Maybe the resistor is missing.

 

Hi... Pretty sure it's 90 Ohms for FULL. Checked numerous websites and you are the first person to say that FULL reads 140 ohms. I've been thinking the last week it's the gauge, just haven't got my body tuned to lay on the floor (I'm 6'4" with a bad back) to check the readings on the fuel gauge....

I have a spare cluster I will check for resistor.... 

THX

This might be why I got this sending unit cheap on ebay, it seems to be faulty with an incorrect FULL resistance.



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70 2+2 convertible
70 2+2 hardtop
70 Parisienne hardtop

 

 
LT1Caddy


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Date:
Permalink  

seventy2plus2 wrote:

I grabbed a new replacement sending unit from my shelf, it's a Spectra Premium unit. 0 ohms on empty, 140 ohms full (I thought it was supposed to be 90 oms). So, I think your sending unit is working fine, there's a problem with your gauge. There's a resistor across the posts of the gauge, it limits the current going into the tank. Maybe the resistor is missing.

 

Hi... I checked for the resistor, still attached.

We're getting it narrowed down. I have to find out how to check the operation of the gauge....



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