GT6 mk 3 All gauges not working

[Pbruce9393]

I am confused. My GT6 gauges (speedo, rev counter, fuel gauge & temp gauge) were all working normally, until I recently replaced the gearbox tunnel with a new one. Now all of them are dead. I assume that I have accidentally pulled a wire off somewhere, but alas a PO has left the dashboard wiring in my car in a messy & non-standard state, and I cannot find any offending disconnected wires ( that weren’t there before). Despite an extensive search through the forum & various wiring diagrams, I cannot find any one reason why all of these would fail simultaneously. I would expect the Rev counter & speedo to fail individually, or the fuel/temp gauges to fail together, but not all four together.

Can anyone advise if there is likely to be one single cause ( a disconnected earth, for example) of this, or am I looking for more than one fault ?

Any pointers or suggestions will be a great help

Thanks

Peter

[dougbgt6]

I can't see how replacing the tunnel has killed these things.

But I would suspect the FUSE BOX!  

The fuse box on the GT6 is not Triumph's best.....innovation.  Squeeze the fuse grippers together and see what happens. Also check engine earths. Do you have a multimeter? 

Some good threads on here about replacing the fuse box. 

Doug

[NonMember]

The fuse box could easily explain fuel and temperature gauges, and if it's a very late (or modified) car with an electronic tacho then it could explain that, too. How it could make the speedo not work, though, is beyond me. But if the speedo drive cable was loose, or the angle drive was about to fail, then catching it while re-fitting the gearbox cover might fail that.

[johny]

If the speedo no longer indicates speed rather than just its backlight failing I reckon there must be more than one problem as, unless theres been a substantial modification, it should be mechanical...

[Nigel Clark]

Do you mean none of the instrument lights are working, or none of the instruments give any reading?

Assuming it's the lighting,  the problem is likely be an accidentally disconnected live feed to the instrument lights (white/red wires), or earth (black wires). 

Nigel

[Pete Lewis]

 

are your speedo tacho actually cable drive ???

well out the box   thought   if the engine earth is missing the starter draws all is current via odd cables  choke speedo  rev counter  they can all  fail with high currents 

i dont see with a std car how refitting the tunnel can fail rev counter  speedo and gauges as none are interconnected 

other than panel lights which wont affect the operation of the dials 

Pete 

[Pbruce9393]

Thanks for all the ideas. 

• The fuse box has been replaced in the past as there is now an 8-way one behind the dashboard at the passenger side, albeit a long time ago, as it is quite a dated one. I did check the output side of all the fuses, and all registered 12V
• What I didn't do was to check the 3-way fuse box in the engine bay. I assumed that had been replaced by the 8-way one, but of course maybe it is still in operation in some shape or form. 
• It does have an electronic tacho, so could be a linked failure of fuel & temp gauges if there is a missing live or earth
• From all the comments, you have convinced me that the speedo is almost certainly a separate fault 
• It was a bright day yesterday, so I need to check the panel lights again, as I can't say if they were working or not
• I guess I also need to check other things to see what else is not working that I haven't noticed yet

Thanks again & I will keep you posted on the outcome of further wire tracing & testing tonight.

Peter

[Pete Lewis]

the orig fuse box has a quirk in the blades that contact the glass fuse caps use the cap to bridge two circuits together  so clean it all up (if its still connected ) 

its unusual for ignition feed to be fused   

Pete

[Pbruce9393]

Update :

• the speedo was a loose drive connection, so fixed now
• The 3- way fuse box appears disconnected. Top fuse was blown, but replacing it made no difference to anything
• checked the 8- way one - all good (12v)where something is connected
• wipers, indicators & hazard warning lights are also not working
• Rev counter is an electronic one & has a good earth at the back, so would suggest the live feed is missing
• All instrument lights (that actually have a bulb fitted) are working

Next task will be to check live feeds to rev counter & voltage stabiliser. Tracing the wires in the rats nest behind the dashboard is a nightmare. Previous mods are very poor - very untidy, wrong colours crimped together, many disconnected / spare cores, etc, etc. Some are taped off & some are just cut,  so it is almost impossible to figure out what was left dis before & which one is the new culprit ! But - will get there

Peter

[NonMember]

Loss of wipers, indicators, fuel and temperature gauges and electronic tacho would be very typical of a blown "green circuit" fuse on the original wiring. However, that wouldn't take out the hazards as they're on the "purple circuit". All lighting comes off the "brown circuit", unfused. However, the presence of a second fuse box does suggest that your wiring isn't as shown in the workshop manual.

People who add fuse boxes to their cars, if they are competent and sensible, will draw up a corrected wiring diagram and store it somewhere safe. Sadly most people are anything but competent or sensible when they hack around modify classic car wiring. As you've inherited this wiring mess from a PO I doubt it's fit for purpose - just on a purely statistical basis that every Triumph I've ever owned has had wiring mods by previous owners that were simply not fit for purpose. You need, unfortunately, to bite the bullet and trace those wires all the way through, draw up what you find, then decide what needs to be fixed. Alternatively, rip it all out and start again, because that might prove quicker.

[DVD3500]

14 hours ago, NonMember said:

eople who add fuse boxes to their cars, if they are competent and sensible, will draw up a corrected wiring diagram and store it somewhere safe. Sadly most people are anything but competent or sensible when they hack around modify classic car wiring.

Hence why I was looking for some software for mine. 😄

 

[Pbruce9393]

Well - it is fixed !  Thanks for all the help & suggestions.

Those of you who said it was the fuse box, please take a bow. Despite me bypassing the top fuse (in the 3-way fuse box) with 2 x crocodile clips & a piece of wire last night, all to no avail, that is what it was. Not just the fact that the fuse had blown, but as Pete Lewis suggested, a clean up with some emery paper & a squeeze together of the blades did the trick. And a new fuse, obviously. 
Fuses 2 & 3 are dead. My biggest mistake was thinking the fuse 1 was dead too, but I know now.

Next little project will be a major tidy up of the wiring & a new diagram.

Thanks again to all who helped.

Peter

[Pete Lewis]

good when the solution is simple to fix and cheap   pleased its working better