Revolution Posted January 23, 2016 Report Share Posted January 23, 2016 Hi Everyone Umm, I know this has been done to death but....... . I recently sent my Temp Gauge off for a service mainly because it was recording too hot on the gauge...towards the red I have checked all the usual cooling issues and substituted senders, voltage regulators but all with the same result. I understand the gauge is reading correctly So I asked the company who serviced the gauge if they could callibrate the sender to the gauge for me and they sent me the following: "the correct sender resistance for your unit is as follows; COLD = 250ohms & HOT (full scale) = 25ohms (voltage stabiliser required) This is totally different for the earlier "moving iron" units which are as follows : COLD = 0 ohms & HOT (full scale) = 85 ohms (no voltage stabilser) You cannot mix the two & NEITHER gauge will "re calibrate" to suit the wrong sender, neither can you re calibrate the sender/s units/s to suit the wrong gauge I don't think Bi-metal instruments had been introduced when your car was built" So, how can I ensure that I get a Gauge and a sender which match as the sender I currently have is from Intermotor with a red tag.......any views?? Regards, Nick Quote Link to post Share on other sites
Lebro Posted January 23, 2016 Report Share Posted January 23, 2016 When you switch on ignition (with a hot engine), does the gauge rise slowly. or does it jump up quickly. If slowly, then it is the later gauge - bi metallic hot wire type, & needs the second type of sender (cold= 0 ohms) + a voltage regulator. If it jumps up, then you need the second type of sender (cold=250 ohms), & no regulator. Bob. Quote Link to post Share on other sites
RobH Posted January 23, 2016 Report Share Posted January 23, 2016 Both Moss and Rimmer list sender type GTR104 for the 4/4a. The later one seems to be GTR108 as for the 5/6, so presumably you need the later one if the refurbishers are correct. Easiest way to be sure is to short the sender wire to earth at the engine via a 22 Ohm resistor (a few pence from Maplins). If the meter reads around zero you need the 0 Ohm-when-cold type, If the meter goes full-scale you need the 250 Ohm-when-cold type. (The resistor is to prevent overranging the meter if its the later type - though you could probably get away with just shorting the wire direct if you didn't do it for too long). If you have a resistance meter you can check the sender. Put the sender in your fridge for an hour or two and then measure the resistance for the low end. Then plonk it in boiling water to check the other end of the range. Quote Link to post Share on other sites
peejay4A Posted January 23, 2016 Report Share Posted January 23, 2016 Somewhere on the forum there a many stories about the variability of senders, even amongst those bearing the same part number. I went through at least three before finding one that gave sensible readings checked against a non contact thermometer. The quality of the repros is pretty poor in this respect. Quote Link to post Share on other sites
Revolution Posted January 24, 2016 Author Report Share Posted January 24, 2016 Bob, When I turn the engine on with the car hot, the needle gradually rises up to hot....no sudden jumping If I contact Moss, presumably they will be able to send me the correct sender if I explain? The Fuel Gauge is fine Many thanks for your advice Nick Quote Link to post Share on other sites
Lebro Posted January 24, 2016 Report Share Posted January 24, 2016 Nick. I can't say how many variations there are for your type of gauge (later type) but I do have a further question. You say the gauge reads too high. Do you mean with a cold engine it goes up to the top, or that it starts off reading cold, but then as the engine warms up it moves up to beyond the correct reading. If the latter, then it would be worth checking out the voltage regulator. (the one behind the dash, not the big one for the dynamo !) It should have two connectors with wires on, & an earth wire to connect the casing to ground. if the earth connection is not good, then the voltage out will be the same as voltage in, & the gauge will read high. (the fuel gauge would also read high as it works the same way). Also, have you tried RobH's test above ? Bob. Quote Link to post Share on other sites
Revolution Posted January 24, 2016 Author Report Share Posted January 24, 2016 Bob, The gauge starts off reading cold but then moves up as the engine warms up It could be the voltage regulator but I have substituted 3 different ones and get the same effect......they all seems to be earthed ok Havent tried Rob's test yet but am veering towards the TR5/6 sender as the answer Regards, Nick Quote Link to post Share on other sites
AlanT Posted January 24, 2016 Report Share Posted January 24, 2016 There is a definitve explanation, by Stuart I think, on here somewhere, of the types of sender, their resistances etc. You won't find it however, unless you do a Google search like this: site:www.tr-register.co.uk temperature sender Quote Link to post Share on other sites
Revolution Posted March 3, 2016 Author Report Share Posted March 3, 2016 Hello Everyone Well I seem to have had a happy ending but as usual with some of my usual "numptiness" along the way! It seems I had an original Temp sender, a later Temp Gauge and the wrong Voltage regulator fitted so no wonder I was getting unusual readings!! Classic "numptiness" was that I had replaced the Voltage regulator with a new one but had not remembered that my car is negative earth and therefore it had no regulating effect (probably burned out)! I replaced it with a TR6 version (neg earth), fitted a "white" collared Temp sender unit and now have some realistic readings on both the Petrol / Temp Gauges Hooray! Cheers, Nick Quote Link to post Share on other sites
Lebro Posted March 4, 2016 Report Share Posted March 4, 2016 I assume you are talking about a modern electronic voltage regulator, as the original type would not be polarity sensitive. Bob. Quote Link to post Share on other sites
Rawls Posted June 16, 2016 Report Share Posted June 16, 2016 (edited) Sorry to reserect this thread again, but there are so many variables that I cannot find anything in the search facility that matches my (similar) problem. TR4A 1965 Changed the voltage stailiser for the original type, both temp and fuel gauges worked briefly, then temp went up to the 'H' section, checked the engine and it's running at normal temperature, fuel gauge still working normally. The temp gauge moves ever so slightly from cold when the ignition is turned on (up to the 'C'), I pulled the connector to the temperature transmitter and earthed it and the needle went straight to H, this shows gauge is good, right? I tried a new temperature transmitter from Intermotor pn 52710 which I believe is the same as a GTR104 and exactly the same reading. Any advice would be greatly appreciated. Edited June 16, 2016 by Rawls Quote Link to post Share on other sites
Revolution Posted June 16, 2016 Author Report Share Posted June 16, 2016 Rawls I found this to be a tricky problem to tackle due to the variety of temp guages, senders and voltage regulators used in our cars What seems to happen is that over time , the wrong combination gets used and hence the reading on the gauge becomes unreliable There is also the question of "quality" when it comes to these parts Personally, I would make sure the temp is more or less correct by manually using a thermostat in the radiator when the engine is running at normal operating temperature and then find the combination of sender/voltage regulator which will give you a fairly accurate reading Good luck! Nick Quote Link to post Share on other sites
Rawls Posted June 16, 2016 Report Share Posted June 16, 2016 Hi Nick, Thanks for your reply, I have driven the car for several miles with absolutely no over heating issues, but I haven't been able to accurately check the temperature, it certainly felt normal. I haven't had the car that long so who knows what combination I have going on? In one of the threads I was researching, someone talked about a dry temperature transmitter/sensor, and no water coming out of the housing once removed. No water came out of my housing once I removed it, but it wasnt exactly dry. Is this normal - could I have some sort of blockage in this area? Mike Quote Link to post Share on other sites
stuart Posted June 17, 2016 Report Share Posted June 17, 2016 You may well have an air lock by the sounds of it. There are a number of temperature senders some are full scale at 100 and others are full scale at 110. You need a 110 version. Stuart. Quote Link to post Share on other sites
Rawls Posted June 17, 2016 Report Share Posted June 17, 2016 Thanks Stuart, I'll check for the air lock. Is the 110 equal to the GTR104? Quote Link to post Share on other sites
stuart Posted June 17, 2016 Report Share Posted June 17, 2016 No idea as I buy them from my local motor factors and they tend to be more reliable. Stuart. Quote Link to post Share on other sites
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