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Today was the day....been watching my fuel consumption so my tank would be near empty (came close....about 6 gallons left), so I could put in a never used (never dented! ;-)) tank and a working sender in my 70 sportsroof.

Took the old tank out and popped the new one in.....cut a generic rubber filler hose off, correct style hose won't fit under my hose clamps....looks like a quick run to pep boys tomorrow!!

Hooked up the wire, turned the key on, still no reading. Voltage at the sender connection swings all the way to 11V and back every second. Wonder if this is normal?

Remember having a second IVR in the basement, I'll give it a shot. Now temp reads half when the motor hasnt run in 24HRS and the gas reads half.......nope!!

Try tweaking the first IVR...several times......still swinging up to 11V and back.....getting tired of diconnecting the battery and pulling the cluster, but know the main power in is on the circuit traces at one end of the cluster all the time....pulling cluster 10 times is better than frying wiring harness!!!

Wife is at work, BTW...no parts runs for today!!

Decide to look at old sender.......how about that.....a float full of fuel...havent seen one of those in a while!!! Ohms out 10 full, 55 empty......not too shabby....think I'll take the cover off the potentiometer and dress the element up and track down a new float.

Should have checked the new sender's resistance at different positions, but I know how much fuel is in the tank. Should have also checked to see if the float arm needed bending so the float reached the top and bottom of the tank....dumb me!!

Suddenly remember the old cluster in the basement.....guess I'll compare guage readings.....HMMM, DOES IT HAVE A IVR ON IT? YES!!!! WOOHOO!!!

Slap it on, now get a 1/8 reading....the sender connection fluctuates between 4 and 6 volts or so (on my cheap multimeter).....I'll see how it reads full after I get some hose clamps.

Still gotta go back out and reinstall the dashpad that looks like the desert (cracks from hell......maybe next year I'll shell out the ridiculous prices they want for 69/70 dash pads)

And the icing on the cake....I remember how some of my VMF brethren have had sealing problems around the sender they put in after a few days......if that happens, I WANT GOD TO KILL SEVERAL KITTENS FOR EACH DUMB POST!!! Got my sender and o-ring from NPD, crossing my fingers!!

I figured I post my experiences today both to blow off steam and hopefully help others. Good luck to others doing this job!!
 

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The IVR is a thermal device that pulses between 12v and 0 volts. It averages out a voltage suitable for driving the instrumentation, typically 5-6 volts. You can't read this with a DVM or analog multimeter set to DC since the voltage is constantly changing. Try setting the meter to a/c and if the meter has wide enough bandwidth (to measure pulse waveforms) then it should read somewhere near 5 vac (rms).

The easiest check for the guage is to simply ground the wire that attaches to the tank sensor. When you do this, the tank indicator will read "full". If the tank indicator does not read "full" then its likely the IVR.

Once you establish the tank indicator and IVR are okay then you can work on the tank sensor. The first check of the tank sensor is to make sure its installed correctly. The fuel pickup tube must be lowest in the tank (facing down). If the tank is empty, an ohmmeter connected between the tank sensor and the tank body should read about 80 ohms. If the tank is full the reading should be about 10 ohms. Be sure the tank is grounded to the body of the car...I mean after using the sealant around the lip and depending on what fasteners you used, you may not have a good ground between the tank and the car body. It never hurts to add a short piece of wire between the tank and the frame of the car.
 

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when i replaced my sender i had a job trying to seal up the thing , the gasket they sent with the new unit was kind of square, so i went to a special seal place and bought a slightly bigger round one made out of a special rubber compound, nitrial rubber or something like that and it was compatable with all fuels.The extra cost was worth it in the long run and don;t forget to use a brass punch on that retaining ring,
good luck/forums/images/icons/smile.gif
 
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