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10-06-2019, 11:57 AM | #1 |
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Location: South San Francisco CA,
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Ohm Meter
OK. I have done a quick search and am having problems. So I am going to throw myself on the sword here. I have a Craftsman Multi Meter with an Ohm setting. I have been fighting a gas gauge issue and am trying to eliminate all possibilities. Having never used the Ohm function, I am not sure what is going on. I put the Meter on 200OHM setting. Touch the two poles of the gas gauge, which is stock and out of the cluster. The gauge shows a reading but instantly drops until it reads 0. What am I doing wrong here? Please, somebody give me a clue. LOL.
Thanks to all, RR |
10-06-2019, 12:15 PM | #2 |
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Join Date: Apr 2016
Location: Cypress, TX
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Re: Ohm Meter
When you use the ohms function on a multimeter, the multimeter will send voltage through whatever device you are reading. So, if you're connecting to a fuel gauge or other instrument, it will cause the instrument needle to move.
Regarding the readings on the multimeter itself, some times you may get a certain reading and move the probes around a little and the reading will change. This is because as you move the probes, the tips of the probes are piercing through a layer of dirt or corrosion and making contact with good bare metal of the wire or terminal. To find out if your sender is good, you can remove it from the tank and put it on a workbench. Hook up the multimeter probes to the terminal on the sender, and to the round metal body of the sender where it contacts the tank. Then put the multimeter on the 200 ohm range setting and move the float arm. It should go from about 90 ohms when the float is high, to near 0 ohms when the float is low (toward the bottom of the tank). A handy thing to have to help with this activity is alligator clip test wires, which you can get at electronic stores such as Fry's, or online, or even car parts stores such as O'Reilly has them. They are a short piece of wire with an alligator clip on each end. |
10-06-2019, 12:19 PM | #3 |
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Location: TN.
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Re: Ohm Meter
Try testing on the 20K setting.
This will give you a reading of 0.00 with both the leads touched together. The 20 200 and 2000 settings just move the decimal point. .
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10-06-2019, 12:22 PM | #4 |
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Location: Cypress, TX
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Re: Ohm Meter
Here is a thread with good information about the fuel gauge and sender from high octane forum member TBONE1964
http://67-72chevytrucks.com/vboard/s...d.php?t=640615 |
10-06-2019, 12:34 PM | #5 | |
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Re: Ohm Meter
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10-06-2019, 12:28 PM | #6 |
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Re: Ohm Meter
OK. Thanks to all who posted. I first must tell you all that I am not the sharpest tool in the shed, so to speak. LOL.
I cleaned off the terminals with some steel wool, set the meter to 20k and tried again. By touching both the left and the right terminals I was getting a .04 reading. When I touched each of the left and rights with the bottom terminal I got about a .10. So maybe I just had the meter too high? Either way, it is nice to see it doing what it is supposed to do. LOL. I will take the sender out later on in the week. I work nights and am going on duty tonight. Thanks to all who helped. Appreciate it. |
10-06-2019, 07:15 PM | #7 |
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Location: Cypress, TX
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Re: Ohm Meter
If the sender and gauge work outside of the truck with test leads connecting them together, then your next suspects would be the truck wires, fuses/fuse panel, and printed circuit on back of the instrument cluster.
Here is the truck wiring diagram: http://67-72chevytrucks.com/vboard/s...27#post9186727 And here is the wiring of the instrument cluster (gauge cluster): http://67-72chevytrucks.com/vboard/s...36#post7630636 I don't know much about a warning light cluster as my truck has a gauge cluster. You didn't mention which you have. The truck wiring diagram is a little difficult to read if you have a gauge cluster, because it is oriented for the warning light cluster and the gauge cluster connector is off to the side as if it was added as an afterthought. Fuse box info: http://67-72chevytrucks.com/vboard/s...98#post8004798 http://67-72chevytrucks.com/vboard/s....php?p=8562654 Probably too much info, I don't mean to over do it. I guess I better go do some chores. Last edited by dmjlambert; 03-18-2023 at 11:01 PM. Reason: corrected link to wiring diagram |
10-07-2019, 02:00 AM | #8 | |
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Re: Ohm Meter
Quote:
Thanks to all who posted a reply Appreciate any and all info. RR |
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