peejay4A Posted January 20, 2017 Report Share Posted January 20, 2017 Marcus is right. Those glass fuses can also go high resistance or open circuit within the glass tube so they look sound but are anything but. I chased that particular fault all over Tywyn. Quote Link to post Share on other sites
4Mal Posted January 21, 2017 Report Share Posted January 21, 2017 I can't remember who deemed, but deem they did. Quote Link to post Share on other sites
stillp Posted January 21, 2017 Report Share Posted January 21, 2017 Well IMO they deemed wrong! Pete Quote Link to post Share on other sites
4Mal Posted January 22, 2017 Report Share Posted January 22, 2017 (edited) It was in a similar thread in 2012. I had a single solid state that had failed then. Since having one for each - no probs. Well only prob is quality of temp senders but that's another story Edited January 22, 2017 by 4Mal Quote Link to post Share on other sites
Lebro Posted January 22, 2017 Report Share Posted January 22, 2017 Should be perfectly capable of driving two instruments Bob. Quote Link to post Share on other sites
Steves_TR6 Posted January 22, 2017 Report Share Posted January 22, 2017 I have a solid state reg for the fuel/temp and its been reliable for 4 years. I did notice that with 'everything' turned on ( lights,wipers,heater) both fuel and temp readings would drop. Investigation showed that the alternator could not hold the voltage up adequately under these contituons, it was dropping to about 12 v. New alternator cured the problem, with reliable 13+ volts (after initial higher reading to replenish battery after starting) I concluded that the solid state regulator needs 2-3 volts to work with, and could not maintain the 10v that the instruments need if the alternator was only holding the voltage up to 12ish. Steve Quote Link to post Share on other sites
RogerH Posted January 22, 2017 Report Share Posted January 22, 2017 Hi Mal, you may have been unlucky with your first regulator. Ideally the input and output should be protected against ringing/resonance with some damping capacitors - see circuit below. With the current drawn by two gauges ( quite small) the resonance may have been a bit excessive and caused it to burn out. Having two in parallel would reduce the current and may reduce the harmful effects of the resonance. Hi Steve, most regulators need apprx 3V above their output to function. However as the input voltage increases you have the problem of getting rid of the dissipated power/heat Only a guess but I'm convinced. Roger Quote Link to post Share on other sites
Lebro Posted January 23, 2017 Report Share Posted January 23, 2017 3V is probably a bit pessimistic, 1.5 - 2 would be more normal. "Low dropout" regulators are even better, but should not be necessary in this case. Bob. Quote Link to post Share on other sites
RogerH Posted January 23, 2017 Report Share Posted January 23, 2017 Hi Bob, a lot of the gumph on the web suggests apprx 2.5v. I normally work on 2v. However with the gauges requiring 10v and the system providing between 12v and 13.7 there isn't a great deal of leeway. But it normally works. As you say 'low dropout' regs could be a better bet but not just yet. Roger Quote Link to post Share on other sites
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