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 Post subject: Fuel gauge not working
PostPosted: Wed Sep 23, 2015 11:21 am 
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Sender has been pulled and checked out . Manual says something about 8.5 volts off the regulator that is tied into the temp gauge , but temp gauge works good . I grounded the lead to the sender and the gauge only goes to in between 1/2 and 1/4 . so gauge is working . Do I need a resistor ? direct power spliced into it ? This is my 78'


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PostPosted: Thu Sep 24, 2015 9:40 am 
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I wrote down some notes on how to diagnose this issue in my manual,my hen I get off of work I will review them and summarize the procedure for you. There is a "voltage viberater" in the circuit.

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PostPosted: Thu Sep 24, 2015 4:43 pm 
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I looked up my notes and referred to the factory manual and came up with this. I have had to do this a couple times with each time coming up with a bad gauge. The voltage regulator brings the voltage down to 7 volts for the temp and fuel gauge.

Here is a overview of the system

Image

This is the test I found my gauges bad with. Notice the leads are in the upper connections of the printed board. Looking for around 100 ohms.

Image

Here is how to measure the resistance of the voltage regulator. The test after this one I feel is better.notice the leads are at the bottom of the board. Looking for 110 ohms

Image

This test is the tell all on how the voltage regulator is working. Looking for 7 volts

Image

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PostPosted: Sun Sep 27, 2015 7:42 am 
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If you end up needing a gauge I have one out of a '79.

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PostPosted: Mon Sep 28, 2015 10:30 am 
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So some how I have to drop the voltage to 7 volts and power the gas gauge with the lower voltage ? It is funny the temp gauge functions , but it doesn't seem to be consistant . Once it gets over half it goes to the high side4 of normal very quickly.


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PostPosted: Sat Oct 10, 2015 8:07 am 
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So the regulator is built into the fuel gauge . Still working on this .


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PostPosted: Sat Oct 10, 2015 10:14 am 
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Everything ohms out good , butt the voltage is 11 powering the gauges . Looking for a 78-80 Gas gauge


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PostPosted: Sat Oct 10, 2015 3:41 pm 
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Is a 76 one different? If not I got one out you can have...

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PostPosted: Mon Oct 26, 2015 8:27 pm 
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mytmouz wrote:
Is a 76 one different? If not I got one out you can have...


Yes , the 76' is different or I would use the one out of the Yellow truck . Thanks for the offer though . I pulled it apart , well.........about 15 times . Finally found it one of the wires past the built in regulator got up against the main power wire and shorted welding the coils on the regulator causing the voltage to be 11 volts . I found a NOS fuel gauge on Ebay and bought it . Voltage was correct and pulsing like it should . pulled the "new" sender I bought of here out and put the old refurbed sender back in cause it passed the test electrically . Gas gauge works great temp gauge is now correct also .
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PostPosted: Mon Oct 26, 2015 9:17 pm 
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hotrod80 wrote:
Everything ohms out good , butt the voltage is 11 powering the gauges . Looking for a 78-80 Gas gauge


When your testing this is the gauge cluster grounded ? I ask this as i was driving mine when the cluster wasn't wing nutted in and when it moved light got dim & off till i moved it to gain a ground....not sure but this thought comes to mind and maybe grounded it will reduce that 11 to 7v

I'll be playing w/ mine down the road as my gauge is incorrect when full and last week i ran out and sputtered to a near by station
:lol: whew

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PostPosted: Mon Oct 26, 2015 9:43 pm 
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3rdLuvNext2a66MALIBU wrote:
hotrod80 wrote:
Everything ohms out good , butt the voltage is 11 powering the gauges . Looking for a 78-80 Gas gauge


When your testing this is the gauge cluster grounded ? I ask this as i was driving mine when the cluster wasn't wing nutted in and when it moved light got dim & off till i moved it to gain a ground....not sure but this thought comes to mind and maybe grounded it will reduce that 11 to 7v

I'll be playing w/ mine down the road as my gauge is incorrect when full and last week i ran out and sputtered to a near by station
:lol: whew


Yes , if you look at the voltage regulator test it shows it needs to be grounded . I used a VOM and a power probe which has a power and a ground .If it is showing full all the time I would suspect a pinched or shorted wire .


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