Area Representative Kingsley Young Posted October 9, 2016 Area Representative Share Posted October 9, 2016 My Fuel gauge is showing very low, yet when I fill her up, I am putting in about 24 ltrs so with 17 ltrs still to use in a 41 ltrs tank the gauge does not relate that. Is there a process to calibrate the gauge to the sender? Link to comment Share on other sites More sharing options...
Area Representative Kingsley Young Posted October 10, 2016 Author Area Representative Share Posted October 10, 2016 Ahh!! Found old thread on this subject, very interesting reading. Basically. The sender is Crap !! Link to comment Share on other sites More sharing options...
John Vine Posted October 10, 2016 Share Posted October 10, 2016 If there is a way to calibrate, I'd be keen to know what it is. The gauge on my R400D has always seriously under-read. A full tank shows as 3/4 and the motor's still running at minus 1/4. I stopped fretting about it long ago and drive on the trip meter instead.AFAIK, the only cure is to fiddle with the sender float.JV Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted October 16, 2016 Member Share Posted October 16, 2016 Is there a process to calibrate the gauge to the sender?If there is a way to calibrate, I'd be keen to know what it is.Didn't we discuss this once? Once it's known that the sender nominally matches the gauge the next step would be a custom dongle that allowed adjustment of m and c...Jonathan Link to comment Share on other sites More sharing options...
John Vine Posted October 17, 2016 Share Posted October 17, 2016 I think it's been discussed to death over the years! If there's a simple solution (that doesn't involve extracting the pump and bending the float arm), I'd probably apply it. Otherwise, I'm happy to continue driving on the tripmeter (which, on the programmable speedo, can be tuned to a high level of accuracy). Modifying the signal in-flight would be a neat trick, though. What electronic wizardry would be needed to do that?JV Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted October 17, 2016 Member Share Posted October 17, 2016 If by chance the signal voltage was too high at all points on the calibration you could do it by passive resistance, but if not it would need something like an op-amp circuit. It's possible that it's a standard design but I wouldn't know. Cost would be a few pounds. Physically it's going to be matchbox sized with a signal pair in and out and power in. Jonathan Link to comment Share on other sites More sharing options...
John Vine Posted October 17, 2016 Share Posted October 17, 2016 Thanks, JK. I'm wondering if I might just bend the needle! (Assuming I can break into the gauge.)By way of research, I've just emailed Caerbont themselves to see what they suggest. I'll post up what they say.JV Link to comment Share on other sites More sharing options...
RedCat7 Posted October 17, 2016 Share Posted October 17, 2016 See Aerobod's solution here https://www.lotus7.club/forum/techtalk/any-way-recalibrate-fuel-gauge?page=1I bodged in the resistors between the gauge terminals to see if it works 18 months ago. It did and has ever since. Link to comment Share on other sites More sharing options...
John Vine Posted October 18, 2016 Share Posted October 18, 2016 I've just emailed Caerbont themselves to see what they suggest.Received a very prompt response. They asked me to supply some sender resistance readings (tank full and "empty") so that they could determine the sender characteristics and then suggest the next move. It'll take a while to collect the data. I'll report back.In the meantime, I think I'll experiment with Aerobod's solution (thanks for the link, RedCat7).JV Link to comment Share on other sites More sharing options...
John Vine Posted April 12, 2017 Share Posted April 12, 2017 Well, I promised to report back. It turned out to be quite a saga, with a distinctly unsatisfactory ending.I started by collecting a set of readings and sent them to Caerbont:I added some explanatory notes: "Tank %" is the proportion of useable fuel remaining (assuming "empty" at 210 miles) Gauge readings are in 1/16ths, so 12/16 is 3/4 full (which currently equates to FULL), and -5/16 is "empty" and off the scale below "R" I measured sender resistance across the black/green and black wires I reset the trip to zero when I fill the tankCaerbont responded by asking me to send in my gauge for recalibration. They proposed to set it to 240 ohms at empty and 26 ohms at full. I sent it to them on 20 January.I regret to say that Caerbont were exceeding slow in dealing with this, not returning the gauge until 27 March. They were also very slow in responding to emails, often not replying at all. Phone calls were about the only way to get in touch.I refitted the gauge last week. Imagine my disappointment when I discovered that it gave the same readings as before! It was as if they'd done nothing at all (which seems unlikely as they'd asked me to provide feedback on gauge performance)I've asked Caerbont what could possibly have happened, and am awaiting their response. I'll report back....JV Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted April 12, 2017 Member Share Posted April 12, 2017 That's an impressive attempt, John. It was as if they'd done nothing at all (which seems unlikely as they'd asked me to provide feedback on gauge performance)How big an operation are they? Big enough to have separate departments for technical work and customer relations? Jonathan Link to comment Share on other sites More sharing options...
John Vine Posted April 12, 2017 Share Posted April 12, 2017 Thanks, Jonathan. Re how big they are, their website doesn't say, but they reported good results for 2016, and they have some prestigious clients (Jaguar, Aston Martin).If I don't hear back by the end of next week, I shall email Gavin Roberts (MD).JV Link to comment Share on other sites More sharing options...
Area Representative Kingsley Young Posted April 12, 2017 Author Area Representative Share Posted April 12, 2017 Really good of you to go to such great lengths John. Kingsley. Link to comment Share on other sites More sharing options...
Wales South AR Posted April 13, 2017 Share Posted April 13, 2017 this company was at stoneleigh last year and may provide the solution ?https://www.spiyda.com/magento/index.php/fuel-gauge-wizard-mk3.html Link to comment Share on other sites More sharing options...
John Vine Posted April 13, 2017 Share Posted April 13, 2017 That's a neat device. But at £44 I think I'll pursue the Caerbont route for now, as to their credit they're doing the recalibration under warranty (yes, even though the gauge is nine years old). The alternative solution may well be aerobod's idea of extra resistors in parallel.JV Link to comment Share on other sites More sharing options...
John Vine Posted April 13, 2017 Share Posted April 13, 2017 Just taken another reading: Sender resistance: 83.1 ohms Gauge: just over 1/16thPreviously, the gauge would have read between 6/16ths and 7/16ths at this resistance. Bizarre. So, it does appear that Caerbont have made a change of some sort -- but not for the better. JV Link to comment Share on other sites More sharing options...
John Vine Posted May 8, 2017 Share Posted May 8, 2017 An update:Took another reading: Sender resistance: 203 ohms Trip meter: 145.7 miles Gauge reading: minus 2/16thsSo, it appears that the gauge is behaving exactly as before, and that the recalibration has had no effect at all. Having heard nothing further re my recalibration feedback, I sent a formal complaint to the Caerbont MD on 24 April. I received an acknowledgement the same day, with a promise to investigate and respond by "early next week" (that is, by 3 May, say). So far, I've heard nothing.JV Link to comment Share on other sites More sharing options...
John Vine Posted June 12, 2018 Share Posted June 12, 2018 I've just realised, over a year later, that I never reported back on this.I received this response from the MD on 12 June 2017:"I have investigated your complaint , it seems that the work [the engineer] carried out was speculative on his part , and he did this without any charge to yourself, and we do not know whether your sender is standard that was his assumption.The only solution I can see is that we build a stepper motor 270 degree gauge that matches the readings you have given us from your sender unit , there will be a charge for this because it will be a custom gauge .Please note that we supply fuel gauges to Caterham who are an OE manufacturer and have no issue with accuracy of the gauge / sender combination."I had no wish to incur the expense of a custom gauge, so didn't pursue it. I will probably investigate aerobod's solution, but the snag is that, as far as I can tell, my gauge is no longer "standard" following Caerbont's recalibration attempts. In the meantime, I'll continue to drive on the trip reading.JV Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted June 12, 2018 Member Share Posted June 12, 2018 For anyone other than John: electronic adjuster modules that match senders to gauges are available. Jonathan Link to comment Share on other sites More sharing options...
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