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Discussion Starter #1
I'm try to sort though a couple of electrical problems.
My fuel guage is not working...I have a wiring diagram but not sure exactly how it
works. The guage is pegged full all the time.
Looks like the pink wire at the guage is a common power wire with other guages which are
working. The tan wire has power att the harness connector which is in the trunk just
before it goes through the rubber grommet. Disconnecting the connector in the trunk has no affect on the guage. The sending unit ground is okay. On modern guages I always just grounded the sending unit wire which would peg the guage which told me the guage was okay and the sending unit was bad.
Whats the best way to diagnose the problem?
2nd issue is on the altenator. I had basically bypassed the old altenator circiuit
and ran my own wiring for and internally regulated unit. The altenator works fine. I'd
just like to tap in so the gen. light is operable with the altenator. Any help here?
68 Malibu.
thanks a bunch.

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Importtech

68 chevelle

my webpage
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Both of these are covered in the Tech Reference section. I'd try to explain it, but I think Wes does a better job than I could.

Alternator

You basically run a wire (hot when key is on) to the light and connect the ground side of the light to the #1 terminal on the alternator. If it's a one wire alternator, you may have to remove a jumper somewhere because it will now be excited and regulated through the light circuit.

Look at the diagram on the right.



And here's the tech ref for the fuel gauge.

Fuel Gauge

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My Web Page (updated 11-22-02)

"Long Live Freedom!"

Chad Landry
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'68 El Camino

[This message has been edited by cjlandry (edited 11-24-2002).]
 

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It should go to empty when you ground the sending wire. It will always read full when you have an open loop.
 

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Discussion Starter #7
Well the guage goes to empty when the sending
unit wire is grounded. I guess thats a good
sign. Can I use a pot to dial in the desired
resistance on the tan wire verify the guage
is accurate? If so then I'm down to the sending unit right?

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Importtech

My 68

my webpage
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I had a similar situation and replaced the sending unit. I filled the tank and it never worked afterwards. Kind of a pain, since you need to remove the gas tank.

But, everything seems to be working once I changed the sending unit.
 

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<BLOCKQUOTE>quote:</font><HR>Originally posted by Importtech:
Well the guage goes to empty when the sending
unit wire is grounded. I guess thats a good
sign. Can I use a pot to dial in the desired
resistance on the tan wire verify the guage
is accurate? If so then I'm down to the sending unit right?
<HR></BLOCKQUOTE>

I think it's a safe bet that you're already "down to the sending unit".

Of course, if you have a 0-90 ohm pot, it would work fine for checking the gauge. I'd even go so far as to say that if you have a resistor valued at just below 90 ohms you could just check to see if it comes near full. I couldn't tell you the "sweep" calibration of the gauge though. I've always noticed that fuel gauges take their time going from "full" to "3/4", a little quicker from "3/4" to "1/2", and they drop from "1/2" to "empty" really fast.

Marketing psychology perhaps?




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My Web Page (updated 11-22-02)

"Long Live Freedom!"

Chad Landry
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'68 El Camino
 

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Import (Jack?)
A pot from the tan sending wire, to ground, will work providing the gage has a good ground. 45 should be around the midpoint and 90 is full. If it's the sending unit shop around. Found some GMs in North Carolina for my 64 beating everyone's price. If you buy a sender get a new gasket and lock ring.
 

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Discussion Starter #11
John and Chad
Thanks for the help..Finally got a chance today to do a little more checking. Sure enough when I dialed in aprox 45ohms the guage went to half full. So I'm faily confident the guage is okay. One interesting thing though. I had a really difficult time
finding a good ground for the pot. Finally got it to work on the trunk latch striker.
Decided to do a continutity check on the tan pigtail of the sending unit to ground...
Read infinity... So decided to Run continuity
from sending unit ground (black wire) to the
body right at the mount point...also read open? Whats the possibility of poor body ground? Where are the ground straps for the body? Maybe I should run a redundant ground for the sending unit some where else to see if it starts working?
Thanks

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Importtech

My 68

my webpage
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Body ground wire is from the battery (-) to the right inside fender. Checked between the sender body and the car body. Maybe the sender ground wire opened??
 

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Doesn't the sender wire attach to a terminal on the sender itself. Not suggesting you pull the sender but the sender black wire is crimped onto the outside of the sender or the sender body. One side of the internal rheostat is tied to the sender frame. The swinger is tied to the center sender terminal. Measuring right on the sender should give you a value equal to what you think you have in the tank.
*EDIT*
Pieces of a coat hanger with one end sharped make good long meter probes if you need them.


[This message has been edited by John_Muha (edited 11-26-2002).]
 
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