Re: [Amc-list] Fuel Guage AMX

[Tom Jennings <tomj@xxxxxxx>]

Don wrote:
> Okay all you electrical wizards, some ideas please.
> After running out of fuel I decided that it was time to fix the fuel indication on my 70 AMX.
> I drained the tank and took out the sender.
> Checked the resistance, and it was within specs.
> Changed the voltage regulator on the dash panel with another (not new) one.
> Right now the fuel reads full an a known empty tank.
> Disconnected the wire from the sender on the tank and the guage still moves quickly to full when the key is turned on.

That last is the test -- the gauge should read E when disconnected.

There's a wire shorted to ground somewhere.

THe sender is high resistance to ground when empty; with a full tank the 
float rises, the wiper moves up the resistance card and it becomes 
nearly a "Short to ground" -- low resistance = full tank.

Dead short to ground -- full tank. Since the tank-full-low-resistance is 
not 0 ohms (dead short: 0 ohms) it doesn't FLING itself up past F, 
normally. Dead short will do that.

Wire could be pinched in the trunk Dunno AMXs but every AMC I've seen 
that damned yellow wire runs through the trunk area just asking jacks, 
spare tires and trunk junk to pinch it.

THere's a bullet connector in the last 2, 3, 4 feet of yellow wire. 
Disconnect that. If it changes things, the problem is "downstream" there.

 > Since I didn't need the stock voltage regulator anymore, I deleted it.
> Now I am having trouble getting the tach to work.

Depends on the type of tach, unfortunately. Two wire factory tach is in 
series with coil +,  some go ground to coil -, etc...
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