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Unread 08-24-2011, 03:06 PM   #1
Tpeal9
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How to measure fuel guage ohms?

Have a 91 YJ and I'm replacing the guages with autometer phantom I have all the guages ordered except fuel. I know how to use a multi meter and everything but when I measure the ohms I got 30 full and 0 empty. I asked autometer and they said I have to take it off and measure the sender without the guage attached to it. Anyone have a diagram of which wires to test on the harness? It it just signal and any ground? Is there an easier way to test it? Maybe under the chassis before the tank?

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Unread 08-24-2011, 07:54 PM   #2
timatoe
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With the sender out of the tank, test it in the full and empty positions. It should be either 0-90 ohms if you had the 15 gallon gauge from the factory, if you already had the 20 gallon set up from the factory it's different but I don't remember the exact numbers. I put a 20 gallon tank in mine after swapping all the gauges and Autometer told me the 0-90 gauge would work and it doesn't, when the tank is full the gauge is completely pegged and the gauge reads 1/4 when empty. They don't carry the other one in a Phantom, but they have a programmable one that's like $130, I'll be getting that one at some point.
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Unread 08-25-2011, 07:45 AM   #3
iowajeepers
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20 gallon tank is the same. 0 - 90 ohm gauge.

I put a GM ( 0 - 88 ohm) gauge in mine and it seems to be close enough.
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Unread 08-25-2011, 09:16 AM   #4
Tpeal9
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Okay I'll test it this weekend and let you know but I have the 15 gallon tank and autometer said it's either 0-90 or 73-10.
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Unread 08-25-2011, 09:38 AM   #5
5.7YJ
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0-90 is the GM version and the 73-10 is the Chrysler version. My 20 gallon tank used the 0-90 ohm sending unit. Depending on the year YJ, there was a lot of GM parts used.
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Unread 08-25-2011, 09:58 AM   #6
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You should also have power disconnected too. The meter uses a voltage it produces to generate the readings. If it's hooked up to the circuit you will get interference from the voltage it uses to do generate the level indication.
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Unread 08-25-2011, 10:05 AM   #7
timatoe
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Quote:
Originally Posted by 5.7YJ View Post
0-90 is the GM version and the 73-10 is the Chrysler version. My 20 gallon tank used the 0-90 ohm sending unit. Depending on the year YJ, there was a lot of GM parts used.
Right, my 20 gallon tank is an older tank from when they actually had the 15 or 20 gallon tanks, it is definately not 0-90. The newer all 20 gallon tanks with the vent tube deal may in fact be 0-90, I don't know on that.
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Unread 08-25-2011, 10:07 AM   #8
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Subscribed. I'll need the same info in a couple months.
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Unread 08-25-2011, 10:33 AM   #9
EdgyAsHell
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Just a word of advice, I spent a few days getting my fuel tank dropped and I was really debating about cutting a fuel door or not. I thought I had a bad ground to the fuel sender. After I put everything back together I realized I was wrong and if not for that fuel door I cut I would have been SOL! I would REALLY suggest you cut a fuel door if you are going to go through the hassle of actually getting your gauge working.
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Unread 08-26-2011, 04:23 PM   #10
Tpeal9
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I didn't have to drop the tank although installing a way to get to the tank through the tub has been in my mind for some time now. Autometer technician told me to take the dash apart (like 8 screws total) and get a reading from the connector going into the back of the gauges. I got a reading of 13 ohms near empty and I just left if apart until I can fill it up and get a reading. I had no clue which terminal was Which so I checked the continuity on the back of the gauges and figured it out. Pretty simple. Im thinking it's the 73 full-10 empty since I was less than a quarter tank and got 13. I'll post what I get when it's full.
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