Discussion
Well i asked this question and cleaned the fuse supplying the Rev counter, Fuel gauge, Temp gauge. I thought the problem had gone away and was happily patting myself on the back saying well done.
The 3 gauges work when they want to, please don't tell me they all do that Sir.
One of you guys kindly sent me a Wiring Diagram so i am all tooled up.
So far i have cleaned the Fuse box contacts and all the spades, they are also nice and tight.
I think maybe the 3 Gauges are all earthed with same wire on a Daisy chain.
I will see if i can get to the back of the Rev Counter and add another earth.
Any ideas
Alan
The 3 gauges work when they want to, please don't tell me they all do that Sir.
One of you guys kindly sent me a Wiring Diagram so i am all tooled up.
So far i have cleaned the Fuse box contacts and all the spades, they are also nice and tight.
I think maybe the 3 Gauges are all earthed with same wire on a Daisy chain.
I will see if i can get to the back of the Rev Counter and add another earth.
Any ideas
Alan
The fuel and temp gauges are fed from a regulated 10V whereas the rev counter is usually fed from the battery voltage (same as clock and voltmeter). The fuel and temp gauges are earthed through their respective sensors so it's unlikely to be a bad earth at the dash for these 2 gauges.
If all 3 instruments stop working at the same time then it's likely to be a common cause which would probably be the 10V regulator or the connections around that (and would mean that the rev counter is also connected to the 10V regulator). If the panel lamps in all the instruments are working and the clock and the voltmeter are working, then the earth daisy chain is OK. if individual panel lamps aren't working then it could be a bad earth at that instrument. However, this shouldn't stop the temp or fuel gauges from working.
I would start looking at the wiring and connections in and around the 10V regulator or even the regulator itself.
GB
If all 3 instruments stop working at the same time then it's likely to be a common cause which would probably be the 10V regulator or the connections around that (and would mean that the rev counter is also connected to the 10V regulator). If the panel lamps in all the instruments are working and the clock and the voltmeter are working, then the earth daisy chain is OK. if individual panel lamps aren't working then it could be a bad earth at that instrument. However, this shouldn't stop the temp or fuel gauges from working.
I would start looking at the wiring and connections in and around the 10V regulator or even the regulator itself.
GB
V6Pushfit said:
10V? Mine are all 12V I believe as bulbs 12V etc
Yes all bulbs are 12V but the temp and fuel gauge are supplied with a regulated 10V to avoid their readings fluctuating as the battery voltage goes up and down with normal charge/discharge cycles.If the tacho, temp and fuel gauge all stop working together then it's a common cause and if the other instruments carry on working (clock, voltmeter) then the fault is almost certainly in the regulated 10V system - either bad connections or a duff regulator. The original is a crude bi-metal strip and capacitor system so won't last forever. There are modern solid state replacements available for not a lot on eBay (eg eBay item number 281963426882). The regulator is usually located on the back of the dash on the right hand side.
Bear in mind that the tacho is not normally supplied from the regulator but seems like it is in your case.
GB
sorry but the Rev counter is 12 volts not 10 volts and is supplied upline from voltage Stabiliser. There is a common supply to Rev counter the supply then continues to Volt stabiliser . Then 10 volts out onto Temp gauge and Fuel gauge.
This is nothing to do with the illumination of gauges.
My conclusion is a problem with supply between Ignition Switch and supply arriving at the Rev counter.
An after thought if the Rev counter has a 10 volt suppy would it operate correctly
The next time the Tacho + Fuel + Temp stop working i will put a supply from Battery to Fuse to prove the problem is not the Ignition Switch .
Alan
This is nothing to do with the illumination of gauges.
My conclusion is a problem with supply between Ignition Switch and supply arriving at the Rev counter.
An after thought if the Rev counter has a 10 volt suppy would it operate correctly
The next time the Tacho + Fuel + Temp stop working i will put a supply from Battery to Fuse to prove the problem is not the Ignition Switch .
Alan
Edited by plasticpig72 on Sunday 3rd April 15:57
Edited by plasticpig72 on Sunday 3rd April 18:43
plasticpig72 said:
sorry but the Rev counter is 12 volts not 10 volts and is supplied upline from voltage Stabiliser. There is a common supply to Rev counter the supply then continues to Volt stabiliser . Then 10 volts out onto Temp gauge and Fuel gauge.
OK - good. If the stabiliser is supplied from the tacho 12V then it sounds like you're on the right track. Good luck and do let us know how you get on.GB
10 or 12 volts -
On the basis you have an 'M' and 'Triumph type' Smiths gauges, then they would normally have a 10V regulator. Earlier models (Vixens etc) had unregulated gauges.
If the tacho stops as well, and it comes and goes, I reckon the most likely is a dodgy earth return somewhere. A lot of the supply and earth is 'daisy chained' along the gauges and so there are a lot of connections - check all the little eyelets are attached, and the backets (and nuts) are tight.
If you have a test meter, check that all the gauge metal cases are at 0 volts when ignition on, and try turning side lights on and off (extra current of the bulbs can help trigger earth problems).
But could also be a dodgy 12v connection somewhere, or loose fuse, or even a broken wire (inside the plastic insulation so it's not obvious).
Can be a bugger to find sometimes, you may just have to go through the wires in detail.
On the basis you have an 'M' and 'Triumph type' Smiths gauges, then they would normally have a 10V regulator. Earlier models (Vixens etc) had unregulated gauges.
If the tacho stops as well, and it comes and goes, I reckon the most likely is a dodgy earth return somewhere. A lot of the supply and earth is 'daisy chained' along the gauges and so there are a lot of connections - check all the little eyelets are attached, and the backets (and nuts) are tight.
If you have a test meter, check that all the gauge metal cases are at 0 volts when ignition on, and try turning side lights on and off (extra current of the bulbs can help trigger earth problems).
But could also be a dodgy 12v connection somewhere, or loose fuse, or even a broken wire (inside the plastic insulation so it's not obvious).
Can be a bugger to find sometimes, you may just have to go through the wires in detail.
RCK974X said:
10 or 12 volts -
If the tacho stops as well, and it comes and goes, I reckon the most likely is a dodgy earth return somewhere. A lot of the supply and earth is 'daisy chained' along the gauges and so there are a lot of connections - check all the little eyelets are attached, and the backets (and nuts) are tight.
The trouble with this is that the temp and fuel gauges don't use any of the earths behind the dash (except for their panel lamps). They are earthed through their sensors - temp gauge through the engine block, fuel sender through the boot earth system. So if these gauges both work intermittently together then it is more likely to be the 10V stabilised supply. If the tacho is fed from the normal 12V and stops working at the same time as the temp and fuel gauges then, as OP says, it's likely to be the 12V supply to the tacho which, in this car at least, then goes on to the voltage stabiliser (in my car it didn't).If the tacho stops as well, and it comes and goes, I reckon the most likely is a dodgy earth return somewhere. A lot of the supply and earth is 'daisy chained' along the gauges and so there are a lot of connections - check all the little eyelets are attached, and the backets (and nuts) are tight.
RCK974X said:
Can be a bugger to find sometimes, you may just have to go through the wires in detail.
Highly likely - always difficult to diagnose wiring problems at a distance!GB
oldgeebee said:
The trouble with this is that the temp and fuel gauges don't use any of the earths behind the dash (except for their panel lamps). They are earthed through their sensors - temp gauge through the engine block, fuel sender through the boot earth system. So if these gauges both work intermittently together then it is more likely to be the 10V stabilised supply. If the tacho is fed from the normal 12V and stops working at the same time as the temp and fuel gauges then, as OP says, it's likely to be the 12V supply to the tacho which, in this car at least, then goes on to the voltage stabiliser (in my car it didn't).
True, and thinking about this comment, I agree.BUT.. BEWARE.. I've had some VERY weird effects from faulty earths in GRP cars.
Something not normally considered - The bulb in each gauge forms a default connection to all the other gauges (through the bulb) from each case to a 'floating' wire (when sidelights off). You only need one gauge (e.g tacho) to use its case as its earth return and odd things can happen if earth wires break/not connected.
The standard Smiths regulator DOES require an earth, and guess what, this earth is typically VIA the SPEEDO GAUGE CASE !!
Some of the tachos use the case as an earth return also, so it's worth a check.
I'm not saying it's likely, but it's possible.....
True story -
I had an earth return wire break in my wedge after taking the dash out (it suddenly started blowing fuses when indicating left [another story]), and the gauges 'sort of' still worked, but a clue was when turning on side lights temp,fuel,volts all went full scale, and tacho stopped. Tacho worked with sidelights off ! Sure, SW gauges, not quite the same but still ....
I worked out this was because the wedge has a VOLTS gauge, so it can become a default earth or voltage supply via its bulb .. and it did use its case as its earth return, and that wire wasn't broken.
I've just removed Tacho to have a look at the connections at the back. One of the power/impulse connections was a loose fit, so i have fitted a new bullet connecter. I have also remade 2 earth wires which were attached to one of the Tacho securing brackets holding it in the Dashboard.
I'll start the car later in the morning, it's only 6.30 at the moment in France.
Alan
I'll start the car later in the morning, it's only 6.30 at the moment in France.
Alan
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