ojh Posted August 10, 2020 Share Posted August 10, 2020 Anybody know of a gizmo that can be used to determine an unknown value for the fuel tank sender? I know its a potentiometer, but I've never seen one that gives a readout of its value as you go thru the range. Thanks Oj Link to comment Share on other sites More sharing options...
Mark Shaw Posted August 10, 2020 Share Posted August 10, 2020 https://www.ehow.com/how_5673060_measure-resistance-ohm-meter.html 1 Link to comment Share on other sites More sharing options...
ojh Posted August 10, 2020 Author Share Posted August 10, 2020 44 minutes ago, Mark Shaw said: https://www.ehow.com/how_5673060_measure-resistance-ohm-meter.html This would work if I had a sending unit. All I have is the Fuel Level Gauge and need to figure out what values for the sender. Link to comment Share on other sites More sharing options...
padgett Posted August 10, 2020 Share Posted August 10, 2020 0-5k pot & DVM would work. 2 Link to comment Share on other sites More sharing options...
John348 Posted August 10, 2020 Share Posted August 10, 2020 Just use a simple ohm meter, all the sending unit is, is an ohm meter measuring the resistance to ground through the variable resistor in the sending unit. I ran into a problem with GM cars. in the mid 70's some cars had a 32 ohm sender and some had a 64 ohm. You are going to have to have it out of the tank to perform this test accurately Link to comment Share on other sites More sharing options...
Frank DuVal Posted August 10, 2020 Share Posted August 10, 2020 OK, he wants to find what sender matches his gauge! Yes, as Padgett says, use a potentiometer, or other variable resistor. Usually 100 ohms or less is needed, but hard to find. You need to find an electronics guy with a large "junk box".😉 Adjust the resistor until the gauge reads Empty, yes, you have to wire a complete circuit as if it was in the car. Take resistor ou tof circuit, use ohmmeter to read resistance. Put resistor back in circuit, adjust until gauge reads Full, remove resistor and read the ohms again. This will be the sender range you need, the difference in the two readings. 3 2 Link to comment Share on other sites More sharing options...
TerryB Posted August 10, 2020 Share Posted August 10, 2020 You might find a test resistor in a scrap electric fuel pump from a Japanese car that uses a built-in sending unit. The electric fuel pump on my Suzuki motorcycle went bad and I replaced it. A potentiometer type fuel sending unit was part of the new pump. In reading about it I found the design was similar to many Mitsubishi built electric pumps for cars and motorcycles. Most times it’s the pump that is shot but the sender is fine. It didn’t appear difficult to remove the fuel gage sender unit from the pump. Link to comment Share on other sites More sharing options...
padgett Posted August 10, 2020 Share Posted August 10, 2020 Guess it would help to know what car. 1 Link to comment Share on other sites More sharing options...
37_Roadmaster_C Posted August 10, 2020 Share Posted August 10, 2020 The year and model of the vehicle will tell almost everything. With a very few exceptions the senders fall into a short list of values. As told above what you need to find the sender range manually is a lower value pot and an ohm meter. A 1K (1000) ohm pot should work great. Hook up one edge terminal to ground and the center terminal to the sender wire. Apply power (ignition On) and adjust as said above for both empty and full. You will then have an accurate range and you can pick the sender that most closely matches the measured range. Do not be overly concerned about the measured and specified values matching exactly, they won't! Just get it close and live with the small error.... One other thing. If the measured range is way different than a standard sender you most likely have a bad fuel gauge or wire or connection somewhere. Fuel gauges are simple meters, but the system can drive you nuts on an old car with old wire and connections. Also, NEVER forget the grounding!! A lot of fuel tanks relied on the straps for grounding. That may have worked when the car was new, but not so much with years of dirt, grime, rust and corrosion. Just saying..... Good Luck, Robin PS: Just a tidbit of information for those that want absolute technical accuracy... The sender is actually a Rheostat and not a Potentiometer. The difference is that a Rheostat only has two connections, one to the fixed end of the resistance element and the second to the moveable contact. A Potentiometer has three terminals, one to each fixed end of the resistance element and one to the moveable contact. Just a bit of overly technical detail. (I would call it a pot in either case and I am retired from the electronic field so I should know better ). 1 Link to comment Share on other sites More sharing options...
ojh Posted August 10, 2020 Author Share Posted August 10, 2020 2 hours ago, Frank DuVal said: OK, he wants to find what sender matches his gauge! Yes, as Padgett says, use a potentiometer, or other variable resistor. Usually 100 ohms or less is needed, but hard to find. You need to find an electronics guy with a large "junk box".😉 Adjust the resistor until the gauge reads Empty, yes, you have to wire a complete circuit as if it was in the car. Take resistor ou tof circuit, use ohmmeter to read resistance. Put resistor back in circuit, adjust until gauge reads Full, remove resistor and read the ohms again. This will be the sender range you need, the difference in the two readings. I found a 0-300 ohm rheostat on Ebay that makes the full pass with less than a full turn of the knob, I can mount it on a plate and add a pointer, use my DOM to create the range on the plate for the pointer to point to. Maybe I'll post some pics of it when I get the parts. This car is a '52 Nash-Healey, I've wanted this type of device for other projects and have assumed it would be commercially available. Thanks, Oj Link to comment Share on other sites More sharing options...
37_Roadmaster_C Posted August 10, 2020 Share Posted August 10, 2020 The article below was copied from a document I found on the web with a simple search for Nash Healey fuel gauge or sender. Anyway you can most likely research the Stewart-Warner D-384C and get the resistance range. Now reversing the direction of the wiper action is all on you . It does appear that you found one of the oddballs I mentioned. 1 Link to comment Share on other sites More sharing options...
joe_padavano Posted August 10, 2020 Share Posted August 10, 2020 1 hour ago, padgett said: Guess it would help to know what car. No, not really. The OP want's to figure out the sending unit resistance needed to operate his fuel gauge. The process is exactly the same, no matter what car it is. As others have already pointed out, you need a variable resistor, an ohmmeter, and an appropriate battery for the car, period. 2 Link to comment Share on other sites More sharing options...
ojh Posted August 10, 2020 Author Share Posted August 10, 2020 1 hour ago, 37_Roadmaster_C said: The article below was copied from a document I found on the web with a simple search for Nash Healey fuel gauge or sender. Anyway you can most likely research the Stewart-Warner D-384C and get the resistance range. Now reversing the direction of the wiper action is all on you . It does appear that you found one of the oddballs I mentioned. I hadn't seen this one, thanks for finding it. Well, one could use a mirror to read the gauge I suppose. I'd like to do better. I am having to make the entire gas tank so the mounting flange is being fabricated anyway. I made the end caps for the tank today. Tomorrow is going to be interesting, I couldn't find any 'terne' to make the tank from so I'll have to create it by leading the entire blank for the tank, incl the inner baffles and end caps. Hmmm. Thats a lot of lead. Link to comment Share on other sites More sharing options...
Frank DuVal Posted August 11, 2020 Share Posted August 11, 2020 (edited) 21 hours ago, joe_padavano said: As others have already pointed out, you need a variable resistor, an ohmmeter, and an appropriate battery for the car, period. Unless you are working on a car with a dash instrument voltage regulator, such as the Standard VRC 601, used in Chrysler and AMC products. In these the fuel gauge does not work on 12 V battery voltage. And I'm not talking new stuff here, these started being used in the early 60s. Edited August 11, 2020 by Frank DuVal (see edit history) Link to comment Share on other sites More sharing options...
joe_padavano Posted August 11, 2020 Share Posted August 11, 2020 6 minutes ago, Frank DuVal said: Unless you are working on a car with a dash instrument voltage regulator, such as the Standard VRC 601, used in Chrysler and AMC products. In these the fuel gauge does not work on 12 V battery voltage. And I'm not talking new stuff here, these started being used in the early 60s. Understood, but my point was that you still need a power source. Link to comment Share on other sites More sharing options...
1930 Kram66 Posted August 11, 2020 Share Posted August 11, 2020 VDO make a gizmo to test fuel gauges called a Gauge Check Model #105-001. Its a 0-300 ohm variable resistor with a ohm value scale on the front face. You simply connect it to the sender terminal of the gauge with the gauge powered and turn the knob to manually operate the gauge ,reading the ohm values at full, half and empty. Hope this helps 1 Link to comment Share on other sites More sharing options...
ply33 Posted August 11, 2020 Share Posted August 11, 2020 I used a handful of resistors from radio shack (back when they were still in business) and combined them in various serial and parallel combinations to get different resistances. I could have used a variable resistor but the ones in the local shop were only rated for a few milliwatts and I was unsure if they were up for the task without overheating. I just cobbled together a series/parallel resistor setup that gave me an empty reading, then measured it using my volt-ohm meter to see what it was (could also have done the math on the resistors). Then I repeated for 1/4, 1/2, 3/4 and full. Turns out there are no volume produced senders that matched up. But using the curve determined from the above procedure I was able to find a universal style that was close for most of the range and then I modified it to work better on the low end of the scale. I wrote up my process and results on my website at https://www.ply33.com/Repair/fuelsender2.html Link to comment Share on other sites More sharing options...
padgett Posted August 11, 2020 Share Posted August 11, 2020 (edited) 1989 Cadillac: Needs a pot. Edited August 11, 2020 by padgett (see edit history) Link to comment Share on other sites More sharing options...
ojh Posted August 12, 2020 Author Share Posted August 12, 2020 17 hours ago, 1930 Kram66 said: VDO make a gizmo to test fuel gauges called a Gauge Check Model #105-001. Its a 0-300 ohm variable resistor with a ohm value scale on the front face. You simply connect it to the sender terminal of the gauge with the gauge powered and turn the knob to manually operate the gauge ,reading the ohm values at full, half and empty. Hope this helps I went looking and couldn't find it under VDO, I did find a reference to it as Continental Gauge Check 105-001, an Australian (I think thats where they were) gauge company that sells VDO gauges and downloaded a considerable list of mfgr sending unit and gauge ohm values, incl water temp, oil pressure etc - a very handy list. But I couldn't find the tool. 1 Link to comment Share on other sites More sharing options...
ojh Posted August 12, 2020 Author Share Posted August 12, 2020 I did find it on ebay as 'gauge check 105.001' and it is from Australia, about $300 AUD incl the shipping. Salty little sucker, no picture available. Link to comment Share on other sites More sharing options...
padgett Posted August 12, 2020 Share Posted August 12, 2020 $156 in the US. $10 for a 0-500 pot and free DVM from HF. Hard choice. 1 Link to comment Share on other sites More sharing options...
John348 Posted August 12, 2020 Share Posted August 12, 2020 (edited) 1 hour ago, ojh said: I did find it on ebay as 'gauge check 105.001' and it is from Australia, about $300 AUD incl the shipping. Salty little sucker, no picture available. What is the year and make of the vehicle you are testing? There is a very simple to do this and not that complicated. and I feel it can be done with out need to purchase equipment you will never use again. if the gauge and sending unit are out of the car even easier Edited August 12, 2020 by John348 (see edit history) Link to comment Share on other sites More sharing options...
ojh Posted August 12, 2020 Author Share Posted August 12, 2020 Maybe I wasn't clear, the car is a '52 Nash-Healey, the sender is totally rotted and unable to get any values from, the manuals do not specify what it would've been. Link to comment Share on other sites More sharing options...
padgett Posted August 12, 2020 Share Posted August 12, 2020 (edited) Post a picture. Odds on it was a stock Nash. How many wires does it have ? Did you try http://nashhealeyowners.com Edited August 12, 2020 by padgett (see edit history) Link to comment Share on other sites More sharing options...
ojh Posted August 12, 2020 Author Share Posted August 12, 2020 Sending units just have the one wire. Link to comment Share on other sites More sharing options...
padgett Posted August 12, 2020 Share Posted August 12, 2020 and the max resistance is ? ps one wire does not make a circuit. Link to comment Share on other sites More sharing options...
John348 Posted August 12, 2020 Share Posted August 12, 2020 33 minutes ago, ojh said: Sending units just have the one wire. The sending unit is in series to ground side of the circuit. There needs to be a feed in and out for it to work. Looks like something is missing from your sending unit Link to comment Share on other sites More sharing options...
ply33 Posted August 12, 2020 Share Posted August 12, 2020 24 minutes ago, John348 said: The sending unit is in series to ground side of the circuit. There needs to be a feed in and out for it to work. Looks like something is missing from your sending unit There is only one wire to the sending unit in my car too. The return path is through the tank to the chassis. Well, maybe not: There is some canvas webbing between the metal parts, so it could be through the metal fuel line that is clipped to the chassis in various places. In any case there is only one wire attached to the sending unit. Link to comment Share on other sites More sharing options...
John348 Posted August 12, 2020 Share Posted August 12, 2020 10 minutes ago, ply33 said: There is only one wire to the sending unit in my car too. The return path is through the tank to the chassis. Well, maybe not: There is some canvas webbing between the metal parts, so it could be through the metal fuel line that is clipped to the chassis in various places. In any case there is only one wire attached to the sending unit. WOW, seems like could become a lot of problems. How does the gauge connect to the sender, electrically? Link to comment Share on other sites More sharing options...
padgett Posted August 12, 2020 Share Posted August 12, 2020 Are a number of senders like that but is very short. The other way to find out is to connect a bridge to the gauge and determinethe values for empty and full. Will probable need to make one, that tank and sender look pretty far gone. If common 0-90 ohms might use one of these. Link to comment Share on other sites More sharing options...
ply33 Posted August 12, 2020 Share Posted August 12, 2020 1 hour ago, John348 said: WOW, seems like could become a lot of problems. How does the gauge connect to the sender, electrically? Pretty much the same way that all the light bulbs work with one wire: Power wire runs from the ignition switch to the dash gauge. On the other terminal of the dash gauge a wire runs to the sending unit. Return path for the dash gauge is through the instrument cluster to the body to the frame. Return path for the sending unit is through the tank to the frame. And yes, grounding can be an issue just like it can be an issue with the lights. Link to comment Share on other sites More sharing options...
John348 Posted August 12, 2020 Share Posted August 12, 2020 I understand it now, so if someone uses a rubber hose in the wrong place could really be disruptive Link to comment Share on other sites More sharing options...
ply33 Posted August 13, 2020 Share Posted August 13, 2020 4 hours ago, John348 said: I understand it now, so if someone uses a rubber hose in the wrong place could really be disruptive Definitely! Link to comment Share on other sites More sharing options...
John348 Posted August 13, 2020 Share Posted August 13, 2020 It just seems like there are way too many places to loose ground Link to comment Share on other sites More sharing options...
1930 Kram66 Posted August 13, 2020 Share Posted August 13, 2020 (edited) Hi Ojh Have you considered carefully pulling the electrical section of the sender apart to allow you to measure the resistance of the winding. If you are lucky and get the thing apart, you might see wear marks on the coil made by the contact on the float arm rubbing on the winding . If this is the case you should be able to get your resistance values by probing the winding and making note of the position of the float arm contact point on the winding at full and empty . You would need to place one ohm meter lead on the earthed end of the coil and take your readings by sliding the other probe along the coil , the value should change as you move along the winding. What could possibly go wrong ,might be worth a shot. Edited August 13, 2020 by 1930 Kram66 Spelling check (see edit history) Link to comment Share on other sites More sharing options...
1930 Kram66 Posted August 13, 2020 Share Posted August 13, 2020 3 minutes ago, 1930 Kram66 said: Hi Ojh Have you considered carefully pulling the electrical section of the sender apart to allow you to measure the resistance of the winding. If you are lucky and get the thing apart, you might see wear marks on the coil made by the contact on the float arm rubbing on the winding . If this is the case you should be able to get your resistance values by probing the winding and making note of the position of the float arm contact point on the winding at full and empty . You would need to place one ohm meter lead on the earthed end of the coil and take your readings by sliding the other probe along the coil , the value should change as you move along the winding. What could possibly go wrong ,might be worth a shot. Link to comment Share on other sites More sharing options...
Dandy Dave Posted August 13, 2020 Share Posted August 13, 2020 1. All you need is a Multimeter. It is handy for other things also like checking voltage, AC or DC, Continuity tests which works out great for checking faulty grounds and such. Olms, to check resistance and it gives you a value. Other stuff that I can't remember right now. 2. Often there is a grounding lug attached to one of the mounting screws. You can run a ground wire from that to a good place to ground like the frame. 3. The wire wrapping inside of the sending unit is a piece of Nichrome wire. If you measure it with a micrometer and get a resistance/ olms reading off of about one inch of it, and know the number of wraps, you could could get a piece and rewind the sending unit yourself if you have the patients to do so. Other wise there are places out there that will rebuild your old nearly impossible to get unit for you. Dandy Dave! 2 1 Link to comment Share on other sites More sharing options...
padgett Posted August 13, 2020 Share Posted August 13, 2020 (edited) That is the Roadkill Mantra. "How many things could go wrong, let me count the ways..." I just wish for once they would find a car with a good cooling system. MBATR. did you find the resistance of the winding ? Edited August 13, 2020 by padgett (see edit history) Link to comment Share on other sites More sharing options...
capngrog Posted August 13, 2020 Share Posted August 13, 2020 With all of this discussion of wires, ohms, electricity and other highly technical stuff, I though I'd look up the proper way to operate a multimeter. I found this most informative video: Cheers, Grog 1 Link to comment Share on other sites More sharing options...
padgett Posted August 13, 2020 Share Posted August 13, 2020 I have a gaggle of DVMs - freebies from HF . Also have a number of more complex ones including two clamp on DC Ammeters And assorted ocilloscopes Have made a few break out boxes also. Electronic tools are a hobby in itself. 2 Link to comment Share on other sites More sharing options...
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