harrytr5 Posted May 12, 2018 Report Share Posted May 12, 2018 Hi, oh sage ones. I have tried everything to bring the temperature gauge to read normal. Substituted the gauge(rebuilt) with another and get the same reading past the H (hot). Changed the Moss thermostat bellows for a genuine made in England bellows (real quality). Changed the thermo switch three times and now using a genuine new, old stock. Clamped the bypass hose and no change. At all times the Lazer thermo gun is telling me 68-80C So not boiling over and has not in 80 miles of driving Rebuilt engine with quality parts and of course not run in. Original new/old qaulity thermostat bellows Pacet fan. Changed voltage stabiliser to electronic one Is the thermo switch not matched to the gauge? What is going on? It is driving me crazy(or not) Regards Harry Quote Link to post Share on other sites
RogerH Posted May 12, 2018 Report Share Posted May 12, 2018 Hi Harry, what car is the problem on. 4 or 4A. The 4A does not need a bellows thermostat. Have you used the correct modern wax stat if a 4A. You say the Laser Thermo gun shows a lower temp 68-80 are you using it correctly. The paint surface (colour and shine) can affect readings. There are different sensor bulbs (see the colour ring around the end). There is a company in Wales that can test the temp gauge properly. Have you tried dunking the sensor bulb in a pan of varying temp water and seeing the gauge response. Roger Quote Link to post Share on other sites
stillp Posted May 12, 2018 Report Share Posted May 12, 2018 Is the fuel gauge reading OK? Pete Quote Link to post Share on other sites
peejay4A Posted May 12, 2018 Report Share Posted May 12, 2018 The 4A does use a sleeved bellows thermostat. At least mine does. Quote Link to post Share on other sites
RogerH Posted May 12, 2018 Report Share Posted May 12, 2018 Hi Pete, I asked the question last week on a similar thread and I was told the 4A has a different size of outlet that doesn't require the bellows stat. Roer Quote Link to post Share on other sites
harrytr5 Posted May 13, 2018 Author Report Share Posted May 13, 2018 Thats interesting Roger,I thought the TR4a had to have one. The bypass hose has an oval hole cast into it not a round one I presume to restrict flow. All other gauges work fine. Yes the Thermo gun works fine although new to me as my other gun decided to pee me off and not work. The engine ticks over not boiling and staring at me with a smirk and defiantly daring me to solve it! Regards Harry Quote Link to post Share on other sites
RogerH Posted May 13, 2018 Report Share Posted May 13, 2018 (edited) Hi Harry, bung in a standard 'Summer' thermostat and see what happens. Roger see post #28 from Stuart https://www.tr-register.co.uk/forums/index.php?/topic/65882-thermostat-gasket/page-2 Edited May 13, 2018 by RogerH Quote Link to post Share on other sites
RobH Posted May 13, 2018 Report Share Posted May 13, 2018 (edited) If the voltage stabiliser is OK It sounds as though the temperature sender is not matched to the gauge. There are a variety of senders with different resistances and using the wrong one will result in an incorrect reading. You say the gauge has been refurbished so I suggest you ask whoever did it what sensor it was calibrated with and then try to source that type. The alternative is to recalibrate the gauge yourself to match the sender, which is do-able though maybe only to get the 'normal' reading right. (if the 'span' of resistance change is wrong its difficult to match over the whole range without fiddling with extra resistances in series or parallel, and probably not worth the effort as you only really need to identify changes away from normal.) Google will give lots of hits for "smiths temperature gauge recalibration", like this: https://www.triumphexp.com/phorum/read.php?9,1405143 Edited May 13, 2018 by RobH Quote Link to post Share on other sites
Lebro Posted May 13, 2018 Report Share Posted May 13, 2018 (edited) Agree with all of above, but I would start by removing the sender from the engine, dunk it in a bowl of water heated to approx 185°F, connect up & compare the reading you get with a known to be good thermometer (i.e. an electronic type used for cooking etc) Only then will you know if the problem is the gauge or the car. Bob. Edited May 13, 2018 by Lebro Quote Link to post Share on other sites
james christie Posted May 13, 2018 Report Share Posted May 13, 2018 Hot water that!! James Quote Link to post Share on other sites
RogerH Posted May 13, 2018 Report Share Posted May 13, 2018 No wonder the gauge is over reading - wow 185'C Roger Quote Link to post Share on other sites
stillp Posted May 13, 2018 Report Share Posted May 13, 2018 Bob, I suspect you've got your Cs and Fs muddled (reminds me of an old joke...) Pete Quote Link to post Share on other sites
stuart Posted May 13, 2018 Report Share Posted May 13, 2018 Thats interesting Roger,I thought the TR4a had to have one. The bypass hose has an oval hole cast into it not a round one I presume to restrict flow. All other gauges work fine. Yes the Thermo gun works fine although new to me as my other gun decided to pee me off and not work. The engine ticks over not boiling and staring at me with a smirk and defiantly daring me to solve it! Regards Harry No need on a 4a as the bypass diameter on the thermostat housing and the water pump body was reduced to negate the need. Stuart. Quote Link to post Share on other sites
Steves_TR6 Posted May 13, 2018 Report Share Posted May 13, 2018 Sounds to me like the gauge may be getting 12v not 10v ( which is what the ‘stabiliser’ averages out tomover time) Or its the sender, or the gauge :-) Its a very simple circuit so you should be able to find the culprit Harry. Steve Quote Link to post Share on other sites
Lebro Posted May 13, 2018 Report Share Posted May 13, 2018 Bob, I suspect you've got your Cs and Fs muddled (reminds me of an old joke...) Pete Was that the Essex girl joke ? Post corrected - I was wondering who would spot that deliberate mistake Quote Link to post Share on other sites
stillp Posted May 13, 2018 Report Share Posted May 13, 2018 Was that the Essex girl joke ? No, that was C and A. Pete Quote Link to post Share on other sites
Lebro Posted May 13, 2018 Report Share Posted May 13, 2018 Thats the one Quote Link to post Share on other sites
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