maybe both.. just have the check each of them to find out... i would suggest the sender as it is harder for gauges to go asthey are dependant on the sender for readings
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91 Chevy Suburban Tonawanda 454 R2500 - SOLD!!! 
04 Dodge Durango 5.7L Hemi 2WD, 24K miles (as of July 2011)
In the past 30 years about 90% of Fords are still on the road, the other 10% made it home.
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