LCD mileometer
Discussion
Hi,
the LCD mileometer on my speedo resets to 0 every time the ignition is turned off, it builds the mileage while running as normal. The instruments are orignial (Griff 500 late 94), black rim with dome profile, normal needle sweep, lcd mileometer and no trip; same as those pictured in SH Bible (sec edition, page 294 top pic). Looks like I will have to send the speedo off to be fixed, thing is I'm not exactly sure of the make. I always assumed they were ETB instruments, they are not the early Stewart Warner, black rim with V profile with reverse needle sweep; nor are they the later Cerbont type with silver rim.
Has anybody had this problem before and can anyone confirm the instrument maker.
Thanks
Ozstyle
the LCD mileometer on my speedo resets to 0 every time the ignition is turned off, it builds the mileage while running as normal. The instruments are orignial (Griff 500 late 94), black rim with dome profile, normal needle sweep, lcd mileometer and no trip; same as those pictured in SH Bible (sec edition, page 294 top pic). Looks like I will have to send the speedo off to be fixed, thing is I'm not exactly sure of the make. I always assumed they were ETB instruments, they are not the early Stewart Warner, black rim with V profile with reverse needle sweep; nor are they the later Cerbont type with silver rim.
Has anybody had this problem before and can anyone confirm the instrument maker.
Thanks
Ozstyle
I have the digital odometer too. In the history file is an invoice from Mole Valley TVR.
One item is listed
Remove and repair speedometer, (replace memory battery).
It then lists mileage before and the records show the 'lost' milage. This was logged with the factory and the documentation to substantiate the actual mileage is there.
When I bought the car it was important to me that I could see the evidence as the HPI check came back showing a milage discrepancy. Without the vendor being up front and able to offer documentary proof I wouldn't have bought it.
Whatever you do, ensure it's all documented, or you may make it more difficult to sell the car.
You could try opening up the speedo and replacing the battery yourself.
I imagine that there should be a permenant live feed to the speedo memory from the car battery and the internal battery should only be to protect the memory in case the car battery is disconnected. Can anyone confirm this?
If so, what has happened to that supply?
Perhaps one of these 'dashboard correction' firms could put the mileage right for you when you have it fixed. It would be better still if you could display the true milage and avoide having to explain to potential purchasers why its low.
One item is listed
Remove and repair speedometer, (replace memory battery).
It then lists mileage before and the records show the 'lost' milage. This was logged with the factory and the documentation to substantiate the actual mileage is there.
When I bought the car it was important to me that I could see the evidence as the HPI check came back showing a milage discrepancy. Without the vendor being up front and able to offer documentary proof I wouldn't have bought it.
Whatever you do, ensure it's all documented, or you may make it more difficult to sell the car.
You could try opening up the speedo and replacing the battery yourself.
I imagine that there should be a permenant live feed to the speedo memory from the car battery and the internal battery should only be to protect the memory in case the car battery is disconnected. Can anyone confirm this?
If so, what has happened to that supply?
Perhaps one of these 'dashboard correction' firms could put the mileage right for you when you have it fixed. It would be better still if you could display the true milage and avoide having to explain to potential purchasers why its low.
Uncle Fester said:
Has anyone figured out how to replace that internal battery without loosing the memory?
The battery must have a finite life and need replacement ever few years.
All of us with the digital type will loose the reading sooner or later unless we find a way around this.
Any ideas?
add another in parallel before you remove the old one.I dont know how practical this is though?The battery must have a finite life and need replacement ever few years.
All of us with the digital type will loose the reading sooner or later unless we find a way around this.
Any ideas?
Uncle Fester said:
Has anyone figured out how to replace that internal battery without loosing the memory?
The battery must have a finite life and need replacement ever few years.
All of us with the digital type will loose the reading sooner or later unless we find a way around this.
Any ideas?
Has anyone looked inside one of these? I can't believe that retaining the vehicles correct mileage is solely dependant on a "battery"? Surely this would not pass any modern SVA regs without some sort of mechanical internal backup?The battery must have a finite life and need replacement ever few years.
All of us with the digital type will loose the reading sooner or later unless we find a way around this.
Any ideas?
I know nothing about the specific LCD unit but at a guess it will use a memory that needs an internal battery backup. There were two ways of doing this, either fit a small battery (usually a watch style button cell) or use a large capacitor. From a design point of view a battery would have been the best option at the time. The battery would have a very long design life as normally the device is powered externally. Effectively the cell life would be the shelf life (typically around 10 years for this type of cell ). If you were designing a similar device now you would probably choose a memory that retains data permanently without the need for a supply (as per modern camera cards and memory sticks) although they tend to be rather slow.
As for correcting the mileage (after replacing the battery) the unit is almost certainly just a pulse counter, can’t see why you shouldn’t be able to convince the unit that you are clocking up miles buy sending pulses to the unit. Provided the input frequency is not too limited you should be able to convince the unit that the car is going quite quickly.
As for correcting the mileage (after replacing the battery) the unit is almost certainly just a pulse counter, can’t see why you shouldn’t be able to convince the unit that you are clocking up miles buy sending pulses to the unit. Provided the input frequency is not too limited you should be able to convince the unit that the car is going quite quickly.
if the reading is still current, then replace the cell with the 12v active. The repair from ETB or ssimilar should be no more than £40, but there is the agro of shipping etc
the 12v runs the memory and cell charging, so if replaced "live" the 12v will hold the reading.
not sure how practical this is on a speedo, but its how our old volatile memory works on our kit.
so if you have an early digital speedo milometer, now is obviously the time to look at it as others are starting to fail.
the cells life will depend on how long and how often "downtimes" are. lots of long ones will shorten battery life, frequent use it will last MUCH longer as the downtime is when the battery is used.Think like a rechargeable toothbrush ;D
BTW if the cell is soldered in, best leave it to a professional, if plug in..fine. If you do chance it on a soldered cell, use a gas soldering iron as its potential is floating so should be fine...a mains soldering iron is earthed and will defo kill the reading and possibly the the milometer!!!
the 12v runs the memory and cell charging, so if replaced "live" the 12v will hold the reading.
not sure how practical this is on a speedo, but its how our old volatile memory works on our kit.
so if you have an early digital speedo milometer, now is obviously the time to look at it as others are starting to fail.
the cells life will depend on how long and how often "downtimes" are. lots of long ones will shorten battery life, frequent use it will last MUCH longer as the downtime is when the battery is used.Think like a rechargeable toothbrush ;D
BTW if the cell is soldered in, best leave it to a professional, if plug in..fine. If you do chance it on a soldered cell, use a gas soldering iron as its potential is floating so should be fine...a mains soldering iron is earthed and will defo kill the reading and possibly the the milometer!!!
Edited by Guillotine on Sunday 16th December 12:53
The 10 years life estimate is probably right. My battery replacement was in 2004 on a 1994 car.
Couldn't we replace the existing odometer mechanism with one taken from a modern donor car?
It only needs a display of the same size to fit the window in the clock face. If necessary, the circuits could be housed separately.
The advantages could be non-volatile memory and modern trip computer functions that were available on the donor car, provided we can feed it the right signals.
Couldn't we replace the existing odometer mechanism with one taken from a modern donor car?
It only needs a display of the same size to fit the window in the clock face. If necessary, the circuits could be housed separately.
The advantages could be non-volatile memory and modern trip computer functions that were available on the donor car, provided we can feed it the right signals.
I like your thinking on replacing with a trip computer. But I'm not sure how straight forward it would be.
I think it would need:
speed input (easy)
RPM input (easy)
Injector pulsewidth to do fuel consumption stuff (harder)
Changing all the "constants" in the trip computer, such as size of injectors, amount of injectors etc... (rather difficult)
It would most likely be easier to start again and code it up on an AVR/PIC. The algorithms themselves are easy enough, and I have written them once
I think it would need:
speed input (easy)
RPM input (easy)
Injector pulsewidth to do fuel consumption stuff (harder)
Changing all the "constants" in the trip computer, such as size of injectors, amount of injectors etc... (rather difficult)
It would most likely be easier to start again and code it up on an AVR/PIC. The algorithms themselves are easy enough, and I have written them once
Ok, it sounds like we have a couple of people here who could make this work.
So ball park figures, how much £ would a conversion cost? Is it economically feasible, given the small number of digital Speedo's out there?
Could the conversion be made to also fit the mechanical odometers? Or at least have two conversion kits with only minor differences?
That way we would have a bigger market and cure the old 'ticking Speedo' problems.
What other information would it be practical to display and what would people want?
I would like outside temperature, oil temperature and amps.
If possible, trigger an audible alarm and switch display to cause of alarm.
For extra brownie points the readings from the ECU would be the ultimate. Trouble is the different ECU's being fitted creates variations.
So ball park figures, how much £ would a conversion cost? Is it economically feasible, given the small number of digital Speedo's out there?
Could the conversion be made to also fit the mechanical odometers? Or at least have two conversion kits with only minor differences?
That way we would have a bigger market and cure the old 'ticking Speedo' problems.
What other information would it be practical to display and what would people want?
I would like outside temperature, oil temperature and amps.
If possible, trigger an audible alarm and switch display to cause of alarm.
For extra brownie points the readings from the ECU would be the ultimate. Trouble is the different ECU's being fitted creates variations.
I can see a need for a decent trip meter & odometer. Possibly the instantanious/average fuel consumption, time to refuel, etc functions of a trip computer if RPM and pulsewidth can be input easily - I suspect injector pulsewidth will be the difficult one as it's ECU dependant...
Outside temp is easy on a 500, provided you're willing to do a bit of wiring or lose the "ice detector". Oil temp and pressure are also easy with the right senders in the engine. We could even reuse the OE pressure sensor if you wanted to lose the OEM gauge. Another nice thing would be alarms for the oil pressure/temperature. Battery voltage is similarly easy. I already have the LCD ECU display (aftermarket ECU) so I'm not too interested in that aspect.
I suspect space would be running out with too much on the LCD - there's only room for one thing to be displayed sensibly, so we can't do too much or it'll be too difficult to control. (The nicest solution is something like a DEFI link system or a Seatalk system that replaces the innards of some of the standard gauges, but no-one would pay the development for that, even if we used off-the-shelf CANbus stuff...)
I'm very willing to aid anyone with support who wants to take this on, but I have very little time for taking on a new project right now. (My skills include requirements decomposition, algorithms, coding & testing
Possibly even I can find a TVR modification company who'd sell the products when they're made )
Probably best mail me (as profile) to take this further as it's going off-topic now.
Outside temp is easy on a 500, provided you're willing to do a bit of wiring or lose the "ice detector". Oil temp and pressure are also easy with the right senders in the engine. We could even reuse the OE pressure sensor if you wanted to lose the OEM gauge. Another nice thing would be alarms for the oil pressure/temperature. Battery voltage is similarly easy. I already have the LCD ECU display (aftermarket ECU) so I'm not too interested in that aspect.
I suspect space would be running out with too much on the LCD - there's only room for one thing to be displayed sensibly, so we can't do too much or it'll be too difficult to control. (The nicest solution is something like a DEFI link system or a Seatalk system that replaces the innards of some of the standard gauges, but no-one would pay the development for that, even if we used off-the-shelf CANbus stuff...)
I'm very willing to aid anyone with support who wants to take this on, but I have very little time for taking on a new project right now. (My skills include requirements decomposition, algorithms, coding & testing
Possibly even I can find a TVR modification company who'd sell the products when they're made ) Probably best mail me (as profile) to take this further as it's going off-topic now.
I would certainly be interested in having a "basic" Trip confuser. Not sure about the fuel economy bit tho...I have a modified TVR..don't want to be scared to death every time I look my fuel economy!.
Outside temp would be good, My red/amber/green light stays amber in the summer and red the rest of the year.
I haveBeen thinking about swapping out my Oil pressure guage for one of those split level gauges ie reads pressure above and temp below. If this could be combined with this one display then i would go for it.
Outside temp would be good, My red/amber/green light stays amber in the summer and red the rest of the year.
I haveBeen thinking about swapping out my Oil pressure guage for one of those split level gauges ie reads pressure above and temp below. If this could be combined with this one display then i would go for it.
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