| j.grif | -- 01-22-2010 @ 6:08 PM |
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Have had wiring problems with the fuel qty gauge system. Believe got it right now. But with the gauge connected to the sender wire and top terminal to wire from fuse block,switch on and holding assy in hand the gauge reads correct for known fuel in tank. But when grounding the assy the needle heads upward to full..whats the deal on that? The oil pressure gauge is out of the car for now. This shade tree mechanic could use some help again. recently purchased sender in place.
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| TomO | -- 01-23-2010 @ 8:06 AM |
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J.Grif, If you have the original sending unit and dash gauge, you should not get a reading when the sending unit is held in your hand and you do not have a grounding wire attached to the sending unit. The circuit for the gas gauge is battery - to gauge, though the gauge coil, to the sending unit wire, to the sending unit, though the sending unit coil to ground and back to the + battery terminal. When the wire from the gauge to the sending unit, is grounded, the gauge will read full. Your description of the results, makes me believe that the sending unit wire is grounded before the attachment to the sending unit. If you have an aftermarket sending unit, the resistance of the unit is too low. Tom
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| j.grif | -- 01-23-2010 @ 9:37 AM |
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Thanks TomO for the help. have checked the sending wire for being grounded and no continuity there. Using a O1A-9275-6v sender and rebuilt gauge. I will go back and recheck the wiring and maybe try another sender,Thanks
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| supereal | -- 01-23-2010 @ 10:12 AM |
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When you ground the wire from the gauge to the sending unit, the gauge should swing to the "full" side. From your description, I suspect that there is a short within the sending unit itself, if you don't find a short between the gauge and the sender. That would account for the needle swing when you ground the body of the sender, which is necessary for the system to function. Put an Ohmeter between the body of the sender and the terminal to see if it is shorted, even when the float arm is moved. I've seen several repro senders that have a short, some along the slider, others in the resistive winding.
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| j.grif | -- 01-23-2010 @ 4:22 PM |
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Thanks Supereal,the sender seems to be ok, no pegging of meter and 15 to 150 ohms when moving float. The sender is a 14-140 ohms by vintique and gauge rebuilt by baxter. Will keep trying for normal ops
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| TomO | -- 01-24-2010 @ 8:20 AM |
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Can you please describe the wiring that you used, when you held the sending unit in your hand and received correct readings and where you connected your ohm meter to get your readings? You have an after market unit and this differs significantly from the King-Seeley unit that your car came with. Your unit is a variable resistance unit and the original units used a coil wrapped around a bi-metal strip with the arm controlling the point gap. You may have to add an external resistor inline with the wire to the gauge in order to get the resistance in the range to operate the gauge correctly. If you have your original tank in the car, I would look for an original sending unit. These can be easily repaired and are very reliable. The same sending unit was used up to 1955 with small changes in arm length. If you have an aftermarket tank, you are probably stuck with the aftermarket sending unit. Tom
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| supereal | -- 01-24-2010 @ 10:34 AM |
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If the sender is an aftermarket type, usually you have to modify the float arm to get a correct reading. It may have to be bent, or changed in length. Even then, most are not particularly accurate. In some cases the arm hangs up on a tank baffle, preventing proper operation. Connect the sender to your ohmmeter, and check the operation. If OK, lower it into the tank and observe the reading. If the needle of the meter pegs when the unit is lowered, the arm is being held up by a baffle or other obstruction. I agree with TomO that the King-Seeley unit is superior, but the variable resistor is reliable, too, if the float arm is the right length and shape. Be sure that the unit base is properly oriented on the tank opening. Depending on the maker, some aftermarket senders require some fiddling to get them to work properly. Most are not as accurate of the K-S original, but we put many of them on, and set them up so they read well enough to tell you if fuel is getting low.
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| j.grif | -- 01-24-2010 @ 3:16 PM |
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Thanks very much for the help TomO and Supereal. I bet you are both right about the sender being at fault. I hooked up the vintique sender in a second 36 with a rebuilt gauge with ign switch on the gage heads to full on the scale just like the first car. Gage in place in second car. Will take my sender to local shop hopefully for tests. The wiring on first car TomO is mostly original harness with exception of 14&16 gage wires from ign switch & bat wire to gauge. The second car (rough) is 14&16 gage wires. Thanks
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| TomO | -- 01-25-2010 @ 7:43 AM |
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JGrif, I did not mean to question the condition of the wiring, I wanted to know how you had connected the sending unit to the gauge. I guess I should have made myself more clear. Tom
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| j.grif | -- 01-25-2010 @ 9:36 AM |
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TomO, Yellow wire from sender connected to lower terminal of gauge and wire from fuse block connected to upper terminal. (oil gauge rermoved). I had these hooked up reversed at one time. Maybe thats what caused the problem.
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