Gauge or sender

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Yote

Yote

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Re: 72 demon
finally put 5-6 gallons of fuel in tank. Gauge moved from below empty mark to empty or barely above. New sender all connections are good. I think it should show 1/4 to 3/8 full . Any ideas?
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My bet would be the sending unit, most of these 'new' units don't function well with the old gauge.
 
They make a device called Meter Match, it is supposed to solve this problem according to their website. Anyone try this yet??
 
It may not be wrong. 80 ohms is empty and no needle movement. Approx' 3 gallons spread on the floor area of the tank ( varies with level/angle ) should generate 73 ohms with result of needle movement up to the first hash mark which is for all practical purposes "go to the pumps/empty". Todays low fuel warning lamp replaced yesterdays reserve/cushion in gauge readings.
Those pumps haven't always been on every corner. I'm sure there are still folks that need to drive down their little mountain to the main road and on some distance to the pumps. One gallon in a tank this size wouldn't do it. Engine stops, power steering and brakes fail. Anyway...
3 additional gallons should get the needle slightly above that first hash mark but again level is a factor.
I can't argue the aftermarket senders for our a-bodies being linear in design and thus wrong between empty and full. The area in question here is where gauge reading matters most.
 
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Mr.FT said:
They make a device called Meter Match, it is supposed to solve this problem according to their website. Anyone try this yet??
Click to expand...


Yes there's a couple of threads on here. I bought one, don't have it in a working car, but I did "rig" it up on the bench. IF it's dependable, it would be one way

But you need to make sure the "original system" is working properly to begin with. If the old gauge is damaged, or sticking, or too far off, likewise if the sender is sticky, has "blank spots" or is "so far off" one of these will only add problems
 
Removed sending unit. After slight adjustment to low stop had the 73 ohms at empty 9.5 ohms when moved to full position, at approximately 3/4 full position showed 23 ohms, at 1/2 position 40 ohms. Jump wired sender to fuel tank sender wire. Set in seat and manually moved sender. Gauge showed empty at sender empty position , VERY slowly moved to 3/4 full mark when sender moved to full position. Any ideas from here ??? Defective gauge ??? Sending unit is new.
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Yes... I'd run it as it is; you have it accurate at empty.

Fuel gauges were not ever designed to be all that accurate. In fact, small aircraft gauges are made the same way (where running out of fuel is REEEEALLY bad news) and they are ONLY calibrated to be accurate at empty. Heck, even my newer cars are not all that accurate; they all take about 1/3 of the total to move from over full down to 3/4.
 
I totally agree with the post above. Empty is empty, full is full, everything between is questionable. Even more so where a aftermarket sender is involved. For everything that the aftermarket changed mechanically to improve about this sender, they also changed it electrically which wasn't improvement.
 
Still confused !!! Re: post #1 and 8. Now have 10-12 gallons in tank, gauge barely comes off empty. Checked grounds, replaced new IVR with old one, same results. Instrument panel grounded at IVR, light switch, and back of panel, all to dash frame. Checked ground at tank. This is going to make me start drinking and I already drink.
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Ok at this point, what you have right now, with the car level, disconnect the sender wire. You can do that easy without jacking the car by getting to the kick panel connector. Separate the connector, and measure the sender wire to ground, CAREFULLY. That is, make certain the meter is getting a good hard ground.

Measure the resistance of the sender and post it.

Also.....

if you have an import "repop" sender, those have a REAL bad reputation about not being accurate

Also, you can't move the sender and estimate "1/2 tank" and so on by just looking at it. You pretty much have to have it in a tank, leveled to operating position.

Last, any chance? the float is sinking?
 
Pulled sender week ago, float is fine. Sender is new. Sender alone shows 50 ohms. Sender from kick panel shows 50 ohms. Sender was from napa, don't know origion. Tank was made in Canada ,assume sender was same. From kick panel connection back to gauge shows 14 ohms if that helps anyone help me.
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Have instrument panel out again #%*. Looking for anything I missed, found nothing. All connections checked good on panel. Is there ANYTHING I am overlooking or can check while panel is out ?? Re: my above posts for other info I've given.
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Yote said:
Pulled sender week ago, float is fine. Sender is new. Sender alone shows 50 ohms. Sender from kick panel shows 50 ohms. Sender was from napa, don't know origion. Tank was made in Canada ,assume sender was same. From kick panel connection back to gauge shows 14 ohms if that helps anyone help me.
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Click to expand...

Well what you need to do is see what the gauge reads, in operation, with "what" readings from the sender. This is why you refer to the test box resistances:

L = 73.7 Ohms (empty)
M = 23.0 Ohms (1/2)
H = 10.2 Ohms (full)

What you need to do is read the SENDER TO GROUND, and compare to the above. Hook it up and see where it reads. If the SENDER is reading 25, then the gauge should read close to 1/2 scale. if not, there's an accuracy problem, or a bad connection in the wiring / terminals

This is ALSO why I prefer to test the cluster......using test resistors and a power supply / battery........on the bench before installing. This gives you a starting place.
 
Del, I did a lot of what you and other FABO members suggested. Refer to my above posts and you will see my readings. I'm definitely not an electrical genius .
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Here is the problem with the data posted: You posted a resistance reading of 50 ohms but it sounds like that was out of the tank; that has no useful meaning. We need to know the resistance reading of the sender in the tank to correlate with the level of fuel in the tank to be able to help.

Please put the float back into the tank as Del said, with a known amount of fuel. Take a resistance reading into the sender with the car level; put one lead on the sender connection and the other lead on the sender's metal base.

IMHO, you have checked the sender out of the tank for empty and 1/2 and full resistances, but the actual float position versus fuel level when the sender is in the tank is not yet known. Nor do we know the actual range of motion of the sender float and arm IN the tank versus out of the tank. You may have to bend the rod to get that right at one level.
 
Here it is again. Sender in tank , 10 gallons in tank, sender reading 50 ohms. Sender in tank ohm reading at drivers kick panel 50 ohms. Out of tank connected to sender wire only at tank with a good ground , at full position on sender gauge registered 3/4 full, at empty position on sender gauge showed empty. Reinstalled sender, gauge showed empty. Testing sender only , full and empty were at EXACT ohm readings given for a properly operating sender. Car was level. At approximately 1/2 level on sender ohm reading was 40 ohms. Every thing reinstalled, continuity on instrument panel checked , new and old IVR giving same results, gauge shows empty.
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Just one more question: With sender in tank, reading 50 ohms and 10 gallons in tank, what did the gauge read? Still near just above empty? I would expect around a 1/4 tank indication with 50 ohms at the sender.

And since you checked and found the same 50 ohms at the kick panel connector, it sounds like your ground and wiring is good.

If the sender is reading 50 ohms with a true half tank, and the gauge is showing empty with just a couple of gallons, then the sender's resistance 'taper' is probably wrong. This is confirmed by your resistance readings in post #8 which are well off from where they should be in the center of the range. Non-linear 'taper' in rheostats was common in the 50's-70's to make variable resistors have a non-linear change in resistance versus position, which is needed in this Mopar gauge system.

If I were you, I would order some 1 watt resistors in values of 10, 22 or 24, and 72 ohms from www.Mouser.com. Connect them one at a time to the sender wire, turn the key to RUN, and see if the gauge goes to full, 1/2, and empty with those 3 values. If so, then the gauge is good and the resistance taper on the rheostat of the sender likely is linear (and therefore incorrect.)

I would also take a resistance reading of the sender when the tank is full. If it is far off of 10 ohms, then the motion of the float and the senders full range of motion is not matched to the tank.

Have you checked the IVR output with your voltmeter? You can do this at either the fuel sender wire or the temp sensor wire with the wire disconnected and the key in RUN.
 
With 10 gallons in tank, a 50 ohm reading, gauge moves from below empty to empty. I would expect a 1/2 to 2/3rds reading on gauge with 10 gallons but not with a 50 ohm reading. I would fill the tank but gauge showed only a SLOW 3/4 reading with sender at full position. Would just have to siphon more out if I need to remove sender AGAIN.
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In case of rallye inst' panel, when everything is OEM and new, viewing angle/skew accounted for,
34 ohms +/- 2 ohms is the 1/4 tank hash mark. No this isn't one of the calibration targets used by service techs. This wasn't even used in building/calibrating the gauges at S-W. Every hash mark has identifying values in the engineered drawings approved by both S-W and Chrysler though.
 
have you checked out your volt limiter it affected my tank gauge readings , was an issue in my 69 gt .
 
Sorry , didn't clarify, not a rally panel. Installed new IVR couple months ago. Reinstalled old IVR with same results.
Getting fluctuating voltage readings on both old and new IVRs. With that I assume both are working properly.
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well hopes out to you to get er fix'd , could tell you about the issues your having . but in the passed with after market gauges , we have had to put a inline radio shack resistors solder as a chain in the sending unit wire to change the gauge readings .
 
Original gauge but replacement sender. Not sure I'm sharp enough to do any electronics beyond what I've already done. At this point some resemblance of accuracy would be an improvement.
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