GW8IZR Posted April 7, 2014 Share Posted April 7, 2014 Unlikely I reckon.. Have you tried taking just the fuel gauge off the panel and just the two wires? It will be dark soon :-) Quote Link to comment Share on other sites More sharing options...
Baldy Mark Posted April 7, 2014 Author Share Posted April 7, 2014 Hi GW8IZR Just in from pickin the boy up! Took the fuel gauge out & fitted the 2 wires to it! Still the same gauge reads full! Attached the vdm & i'm still getting the same readings 12.05v going in & 12.05v coming out! (Green/black wire not connected), Connect the greeb/black wire & the vdm reading drops down to 4.5v! Quote Link to comment Share on other sites More sharing options...
Baldy Mark Posted April 7, 2014 Author Share Posted April 7, 2014 Hi GW8IZR I've been looking around the internet for folk who have had the same problem a myself fuel / temp gauge readng full / hot, one of the things i have noticed is that there is a lot of folk talking about the fuel tank sender unit & the wires that fit the connector! As i had said earlier my gauges were all working fine before i removed the insrument cluster but i'm now wondering about the 3 wires that conect to the tank sender? Can you or somebody confirm that the wires are fitted correctly as i have noticed that some folk have quoted that the middle connection is the earth! But on my sender unit the black wire is fitted to the bottom conection? Quote Link to comment Share on other sites More sharing options...
GW8IZR Posted April 8, 2014 Share Posted April 8, 2014 But that wouldn't stop the temp gauge working? If you only disturbed the wiring at the dash that's the most likely place to look. They are two separate circuits only sharing a common feed. 12v into the gauge, single wire goes off to each sender. The resistance of the temperature sender changes as the coolant gets hot and the fuel gauge is just a big variable resistor that has a float lever - as you use fuel the resistor changes value. As the temperature increases the resistance changes (it gets lower) so more current flows in the circuit. In the gauge there is a small bi-metal spiral closely coupled to a heating element. As the current increases the element gets warm - the two metals expand at different rates so when they get warm they change shape As they unwind the pointer moves. Its so simple it hardly ever goes wrong. Is it possible you left them at full scale for a long time when maybe the wiring was in the wrong position earlier? Quote Link to comment Share on other sites More sharing options...
Baldy Mark Posted April 8, 2014 Author Share Posted April 8, 2014 Hi mate, all i did was remove the insrument cluster & gauges then fit them back together again! The gauges were reading as normal quarter a tank of fuel! & the temp was sitting as normal end of the white bar before i removed the cluster built it all back up pluged in the connectors switched on the ignition to check all was working before fitting the screws (nothing worse than buiding something up only to realise its not right) & the gauges went to full & hot! I was on the internet looking for folk thats had the same problem last night & saw that some folk were talkin about the fuel sender wires, just thought worth a try as it's starting to do my head in now! Hate not being able to fix something i'm lkke a dog with a bone!! Quote Link to comment Share on other sites More sharing options...
GW8IZR Posted April 8, 2014 Share Posted April 8, 2014 I am also frustrated 'cos it should be simple to sort :-) I have made an assumption this is an early 110 - bit late now but we better be sure we are talking about the same thing here :-) What engine / dash is it? Did you ever check the voltage between the gauge case and 0V with the ign on? Quote Link to comment Share on other sites More sharing options...
Baldy Mark Posted April 8, 2014 Author Share Posted April 8, 2014 Yes it's an early 110 The engine is a disco 200tdi converted about 2 - 3 years ago sorry meant to say both gauge bodys read 0v on the vdm Quote Link to comment Share on other sites More sharing options...
GW8IZR Posted April 8, 2014 Share Posted April 8, 2014 OK So no complexity added by TD5 gauges etc, that's good news. Every test so far look good - the ignition feed is good. - the connection to the senders looks good, (you can see the volts drop when you connect the wires but not to zero) Again forgive me for a simple question. If you pull the wire from the temp sender at the cylinder head its definitely the temp gauge that returns to cold? Quote Link to comment Share on other sites More sharing options...
Baldy Mark Posted April 8, 2014 Author Share Posted April 8, 2014 Yes & the same for the fuel gauge diconect the wire & the gauge reads empty! Quote Link to comment Share on other sites More sharing options...
GW8IZR Posted April 9, 2014 Share Posted April 9, 2014 OK the best I can do now is make some comparison readings on mine this weekend and post here. Ridiculous though it seems, from the results of the testing I suspect the gauge(s) - I do find that very unlikely but let me make some measurements to compare. Regards Paul Quote Link to comment Share on other sites More sharing options...
Baldy Mark Posted April 9, 2014 Author Share Posted April 9, 2014 Hi GW8IZR I was back out again last night havin a look & to verify the results that i had posted earlier I have checked all the wires in the dash & i cant see any wire or wire's that i have forgot to connect when building the dash back up! I went through the process you had posted earlier regarding using a vdm & all the reading's have came back the same! Do the fuel / temp gauge connect to the same earth at some point? or do the each have individual earths? Quote Link to comment Share on other sites More sharing options...
western Posted April 9, 2014 Share Posted April 9, 2014 the gauges are linked together on the earth wire which then connects to a 4 or 6 way bullet connector one wire of which is integrated into the earth citcuit of the vehicle, also clean the earth wires at the big screw/bolt in engine bay near the clutch master cylinder, the screw is on the bulkhead with lots of plain black earth wires to it. Quote Link to comment Share on other sites More sharing options...
GW8IZR Posted April 9, 2014 Share Posted April 9, 2014 Back on page 1 of this we had the following test: Now take the red dvm test probe to the metal body of the gauge. It should read almost 0V - as near to zero as possible and definitely not 12V. If it reads 12V the negative connection to the gage is not correct. You need to fix that by re connecting the missing wire that you maybe left off earlier or fix the broken terminal, whatever. You could add a temporary wire from a good ground to the gauge body and re confirm with the red dvm probe it goes to 0V. Now we have been round a few things since then but a couple of posts ago you said: >>sorry meant to say both gauge bodys read 0v on the vdm So I'm assuming the gauges are connected to zero volts. You can put a temporary 0v ( or earth wire if you prefer )from the key switch barrel to one of the gauges to test. Quote Link to comment Share on other sites More sharing options...
Baldy Mark Posted April 9, 2014 Author Share Posted April 9, 2014 Hi western / GW8IZR Western In reply to your post i had a look around the bulkhead for the earth (screw/bolt in engine bay next to the next to clutch master cylinder) i've had a look & cleaned what i could see & still no difference! GW8IZR Yes you are correct! A few posts ago i did say 0v on the gauge body & i had checked it all again step by step as you had advise on a previous post! Just clutching at straws mate trying everything & anything i can think of now! i's stopping me from starting my next job! Don't like starting a new job till the old one's finished! Quote Link to comment Share on other sites More sharing options...
GW8IZR Posted April 9, 2014 Share Posted April 9, 2014 Fully understood Mark, I am perplexed by this and want to get to bottom of it. I'm sure my gauges are not earthed as the dial lamp holders are insulated and when I made the loom I didn't put that wire in.. also the diagram doesn't show an earth wire but it may be implied by the dial light connection. Its possible that there is a shunt regulator in the gauge that requires a 0v connection which is why I asked if the gauge case was showing any voltage.. Until I measure that with my own dvm and eyes there is still a niggling doubt in my mind. But if you put a temporary wire from ground to the gauge it won't hurt and will confirm one way or another. Did you keep the tdi dash instruments when you did the engine swap? Its a pity you haven't got a spare gauge you can borrow for ten minutes. I you are near Anglesey I could help. Quote Link to comment Share on other sites More sharing options...
western Posted April 9, 2014 Share Posted April 9, 2014 the original fuel & temp gauges should have 3 electrical connection [disrefarding the illumination ires] both have a central threaded rod with a U clamp & a knurled nut to secure the gauge & clamp to the dash moulding, the gauges earth wire should be linked [like a daisy chain wire -- vvvvv ] from each gauge including the speedo, connected to each gauges threaded rod with a ring terminal & secured with the knurled nut, these terminals must be clear of every other terminal on the back of each gauge or it shorts out to earth = no worky. the 2 other terminals a spade type one from each sender unit 7 the other on a plain green wire from the vehicles 12v system & both these must be on the correct place on the gauge, IIRC they are marked with + for the 12v green wire, can't remember if the signal in wire from the sender units are marked. as for the bulkhead earth location at least you know these are clean & sound. hope that helps Quote Link to comment Share on other sites More sharing options...
Baldy Mark Posted April 9, 2014 Author Share Posted April 9, 2014 Hi GW8IZR You have lost me at the shunt regulator? Ha Ha When you say put a ground to the gauge! Take it you mean to the bit on the u clamp & not the gauge body? Still the original guages that is fitted! Had to change the temp sensor as the disco one didn't match the gauge but that was all No sorry, i stay in ayrshire scotland! & i would have to stop at every fuel station on the way down cause i dont know how much fuel i've got in my tank! Ha ha! But thanks for the offer much appreciated mate! Quote Link to comment Share on other sites More sharing options...
Baldy Mark Posted April 9, 2014 Author Share Posted April 9, 2014 Hi Western You say the gauges should have 3 electrical connections on them!, I take it you mean green,black,green/black (fuel gauge) / green,black,green/blue (temp) the green wire & the black wire both being like a daisy chain? Regarding the speedo the only wires i have attached to it are for the 2 instrument light's? Should i have a earth wire attached to one of the screwed rods on the speedo? Quote Link to comment Share on other sites More sharing options...
GW8IZR Posted April 10, 2014 Share Posted April 10, 2014 Hi The gauge bodies, the metal stud and the clamp are all in contact with each other. So for testing they are all the same. To confirm this just run a temporary wire from a good 0v point or ground to the screw, clamp or gauge body and see if the pointer falls to a sensible position. I'm still have a little doubt about this as I would have expected to see a voltage on the case if it contained a regulator and you have measured 0v .. so either there is no regulator or you already have an earth.... but its a quick test to confirm so do it. A missing earth from each gauge is far more plausible than two faulty gauges. Quote Link to comment Share on other sites More sharing options...
Baldy Mark Posted April 10, 2014 Author Share Posted April 10, 2014 Hi GW8IZR You say the gauge bodies, the metal stud & the clamp are all in contact with each other! Just want to confirm this the clamps only make contact with the gauge through the threaded rod? & not the gauge body it's self because according to western on page 1 the clamps dont make contact with the gauge body? Quote Link to comment Share on other sites More sharing options...
GW8IZR Posted April 10, 2014 Share Posted April 10, 2014 So the gauge body is metal, comming out of the middle is the threaded rod which is metal and the clamp is metal.. so they are all connected together. Its important that the clamp does not touch either of the two electrical connections. The ground or 0v connection makes contact with the round fixing nut which makes contact with the u shaped clamp Does that make sense? Quote Link to comment Share on other sites More sharing options...
Baldy Mark Posted April 10, 2014 Author Share Posted April 10, 2014 Cheers mate just wanted to confirm that! As i thought the way you were talking the clamps touched the sides of the gauge body as well as the threaded rod? because western had suggested that if the clamps were touching the body of the gauge, that i might have a hort to earth which will make the gauges read to the far right of their scales Quote Link to comment Share on other sites More sharing options...
western Posted April 10, 2014 Share Posted April 10, 2014 Hi Western You say the gauges should have 3 electrical connections on them!, I take it you mean green,black,green/black (fuel gauge) / green,black,green/blue (temp) the green wire & the black wire both being like a daisy chain? Regarding the speedo the only wires i have attached to it are for the 2 instrument light's? Should i have a earth wire attached to one of the screwed rods on the speedo? Yes but the plian green is the ignition controlled 12v feed so ign must be on to get 12v to gauges. instrument lights IIRC have their earth wires linked to the gauge earth wires & the red/white feed to the lighting from the loom. Quote Link to comment Share on other sites More sharing options...
Baldy Mark Posted April 10, 2014 Author Share Posted April 10, 2014 Hi western Your right, the green wire is the 12v feed (ign on), it's just that the way i had read your post it sounded like the speedo had it's own earth mate! Cheers Quote Link to comment Share on other sites More sharing options...
GW8IZR Posted April 10, 2014 Share Posted April 10, 2014 Take a picture of the back of the instruments as they are - post them up and lets see if there is something obvious? Quote Link to comment Share on other sites More sharing options...
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