Geoff Hender Posted January 20, 2017 Report Share Posted January 20, 2017 I have errors on both the fuel gauge and the temp gauge. Fuel gauge is reading half fuel when tank is full and temp appears to be reading half the actual temp. Both errors have occurred simultaneously. Any thoughts as to a reason this could happen? Quote Link to post Share on other sites
Richard71 Posted January 20, 2017 Report Share Posted January 20, 2017 Hi Geoff, This fault usually points towards a defective voltage stabiliser. More learned forumites will be along with further advice. Quote Link to post Share on other sites
TR NIALL Posted January 20, 2017 Report Share Posted January 20, 2017 Yes Check Voltage Stabiliser. Quote Link to post Share on other sites
AndyR100 Posted January 20, 2017 Report Share Posted January 20, 2017 Very likely to be the voltage stabiliser ...... Andy Quote Link to post Share on other sites
Lebro Posted January 20, 2017 Report Share Posted January 20, 2017 +1 Bob. Quote Link to post Share on other sites
D Murton Posted January 20, 2017 Report Share Posted January 20, 2017 I had this on the 4A. Check that the voltage stabiliser has a good earth. Dave Quote Link to post Share on other sites
Geoff Hender Posted January 20, 2017 Author Report Share Posted January 20, 2017 Many Thanks to all Quote Link to post Share on other sites
Lebro Posted January 20, 2017 Report Share Posted January 20, 2017 Actually, I think that a bad (or missing) earth would make the gauges read high, not low. More likely the stabiliser needs replacing. Bob. Quote Link to post Share on other sites
RogerH Posted January 20, 2017 Report Share Posted January 20, 2017 Hi Geoff, if it is a 4/4A then item #44 sounds like the culprit http://www.moss-europe.co.uk/shop-by-model/triumph/tr2-4a/electrical-system/gauges-instruments/instruments-cables-dash-switches-tr4-4a.html if 5/6 the item #11 http://www.moss-europe.co.uk/shop-by-model/triumph/tr5-6/electrical-system/gauges-instruments/instruments-switches-to-c-cr1-cf1.html Get the solid state regulator/stabilzer - it wrks very well. Roger Quote Link to post Share on other sites
john.r.davies Posted January 20, 2017 Report Share Posted January 20, 2017 (edited) Checking the "stabiliser". This device doesn't do what it says on the tin, as its function is to turn the volts off and on again repeatedly. The clever bit is that it does this in a way that averages 10V, while the heavily damped gauges don't notice the Off/On. A faulty stabiliser looks just as good as one that works, but a multimeter - £10 or less - will show the On/Off output. Cycle should be about a second or less. An under reading gauge might be seeing a slower cycle. John Edited January 20, 2017 by john.r.davies Quote Link to post Share on other sites
RogerH Posted January 20, 2017 Report Share Posted January 20, 2017 (edited) Hi Folks, to add to Johns post above. I pinched this from another forum and it is apprx correct. General Operation. The volts, fuel, and temp gauges all operate on the same basic principle: an electric current flows through resistance wire inside the gauge. This current causes heating of the resistance wire, which is wrapped around a bimetallic strip. This strip bends in response to the heating. The gauge's pointer is attached to the strip and the more the strip is heated, the more the pointer deflects. The response time of these gauges to a change in the current is typically about 3 to 10 seconds. So we have a stabilizer/regulator that is clicking on and off to give apprx 10V. And we have a gauge that is clicking on and off to give the value required. - ooops!!! not clicking but simply bending (thanks John) All very ancient but very clever. Why have a voltage regulator? when running the car electrics are only apprx 12V (upto 13.4ish). Any gauge using these volts will vary - not good. So the normal 12V is reduced to 10V. In the pre 70's world reducing stable volts was not simple - and would be an expense. The Smiths/Lucas regulator is cheap and functional AND long lasting. Now a days we use semiconductors - steady 10V at the output. Why have Gauges with bi-metal bits and pieces that operate slowly when other gauges can move quickly. With our simple cars if the fuel sloshed about, the tank sensor would be bobbing up and down. This would make a sensitive gauge bob up and down. The beauty of the bi-metal gauge is that it takes time to adjust to the new contents - so you have a stable and possibly an accurate reading. Smiths/Lucas were very good at what they did. Roger Edited January 20, 2017 by RogerH Quote Link to post Share on other sites
Lebro Posted January 20, 2017 Report Share Posted January 20, 2017 Well explained Roger, you've earned an extra biscuit with your tea Bob. Quote Link to post Share on other sites
john.r.davies Posted January 20, 2017 Report Share Posted January 20, 2017 You slightly miswrote yourself, Roger, as the gauge isnt going On/Off, but heating the bimetallic proportionally to the current permitted by the sensor, and thus reading the level sensed, of fuel or temperature. But you knew that! John Quote Link to post Share on other sites
ianc Posted January 20, 2017 Report Share Posted January 20, 2017 In the sidescreen TRs, the tank gauge does bob up and down when the car is on the move, which (I imagine) is why the change was made for TR4 onwards. Ian Cornish Quote Link to post Share on other sites
RogerH Posted January 20, 2017 Report Share Posted January 20, 2017 Hi John, quite so - many thanks. Roger Quote Link to post Share on other sites
RogerH Posted January 20, 2017 Report Share Posted January 20, 2017 Hi Ian, the early cars didn't have the 10V regulator and probably had a moving iron gauge that responds quickly. Roger Quote Link to post Share on other sites
DaveR Posted January 20, 2017 Report Share Posted January 20, 2017 (edited) If you fit a repro 10 volt solid state stabiliser be careful not to accidentally short the 10 volt, gauge, wire down to earth because on some a series transistor will burn out. The circuit uses a zener diode controlling a series transistor with no short circuit protection, cir cur late 1960's. I have heard of some using a regulator chip with short circuit protection. However, as there is no way of knowing what you are buying be careful fitting the unit. Dave Edited January 20, 2017 by DaveR Quote Link to post Share on other sites
TR 2100 Posted January 20, 2017 Report Share Posted January 20, 2017 Well explained Roger, you've earned an extra biscuit with your tea Bob. Half chocolate-covered. NOT to be dunked! AlanR Quote Link to post Share on other sites
DaveR Posted January 20, 2017 Report Share Posted January 20, 2017 Well explained Roger, you've earned an extra biscuit with your tea Bob. I agree. Dave Quote Link to post Share on other sites
peejay4A Posted January 20, 2017 Report Share Posted January 20, 2017 (edited) Hi Ian, the early cars didn't have the 10V regulator and probably had a moving iron gauge that responds quickly. Roger Balancing coil is the term iirc. Edited January 20, 2017 by peejay4A Quote Link to post Share on other sites
Lebro Posted January 20, 2017 Report Share Posted January 20, 2017 Both right. Two coils - one providing a constant pull one way, & and a second which provides a variable pull the other they are pulling (or pushing) a small piece of iron attached to the needle. Used on fuel gauge only on our sidescreen cars. Bob. Quote Link to post Share on other sites
4Mal Posted January 20, 2017 Report Share Posted January 20, 2017 If you go for the solid state version it is a good idea to have 2 - one for each gauge. I can't remember where I read this, but it is deemed more reliable. I now have 2 Quote Link to post Share on other sites
RobH Posted January 20, 2017 Report Share Posted January 20, 2017 Deemed by whom? That makes no sense at all IMHO. A single properly-designed semiconductor regulator will be perfectly reliable driving both gauges. Its not as if the load is complex. Quote Link to post Share on other sites
RogerH Posted January 20, 2017 Report Share Posted January 20, 2017 Hi Mal, the solid state regulator is easily happy with 1 amp - more than enough. What I have a concern with is that in normal electronic circuits the regulator would have a capacitor at the input and output of it and on the car it is not there. This could kill the reg a little soon. Roger Quote Link to post Share on other sites
GT6M Posted January 20, 2017 Report Share Posted January 20, 2017 (edited) I no no if the TR gauges are fed by same sort of fuse as a GT butt, some times, there is a dodgey contact in fuse box the spades get slack / corroded, this give intermittant faults, just like yer describing this used to happen to my gauges run of the OE fuse symptom here was though, gauges would go doon, an then up a wee bit,, butt, moer doonwards than upwards, till fuse / holder / spade,self sorted, !!! generally a bump / pot hole would be enuff, failing that, a wiggle and a turn of fuse init odder, would work So, check yer fuse an its contacts too. M Edited January 20, 2017 by GT6M Quote Link to post Share on other sites
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