Coolant temperature gauge

[Derek]

The talk about oil and coolant gauges in the Hi from Italy thread (http://forums.ducatipaso.org/viewtopic. ... 5&start=15) made me decide to investigate why the gauge on my 907 has always read high. At switch on the needle goes straight to 175ºF and at running temperatures shows around 205º -210º.
The first thing I discovered was that I had forgotten to take the main fuse out after I took the bike out for it's annual MOT test about 2 months ago and of course because of the lockdown it hasn't been used since. I was very dismayed to find that it's lithium battery was flat. Voltage was down to around 6V so it will probably be scrap now.
Anyway I got an alternative power source on and thinking the sensor might be the problem I disconnected it. Rather annoyingly the gauge still shows 175º and switch on and goes to the top of the scale if I ground the sensor wire as I'd expect.
So it looks like the gauge is faulty.
Has anyone got any ideas for fixing it or maybe a spare from an old dash that they would sell?

[Mc tool]

Bend the needle down

[paso750]

I had a similar problem with the fuel gauge of my Vespa scooter. With ignition off the needle would be on zero. With engine running it would only work between half and full, indicating half when the tank was actually almost empty. Tried replacing the fuel sender and went through the whole wiring but only replacing the fuel gauge solved the problem. Hadn't thought about Hamish' solution

[Mc tool]

Well , Im thinking that since it has "always" read high and Derek did all the right tests so Im thinkin it may have been damaged by a PO ...maybe dropped or just the needle bent, I could see how someone may have damaged the needle and not noticed untill the bike was reassembled and then the owner thinks about the amount of work involved in sorting it and thinks bugger that ,and it stays that way untill Derek buys the bike.

[Derek]

I don't think the needle is bent but it has occurred to me that maybe it could be taken off and repositioned so that it reads a bit more correctly. The trouble is I'd need to power it up with sensor connected and fit the needle in the right place. Easier said than done with the dash in bits.

[paso750]

do you know the exact model of the sensor or an equivalent? If you find a datasheet you may be able to emulate it with a potentiometer or some resistors.

[Mc tool]

Im not sure just how the needle is mounted but if it is on a tapered shaft then I would have a go at remounting it.
Why not use the original sensor , just remove from bike ,wire it up and dunk it in boiling water and set the needle to boiling point( cant remember if its celcius or farenheit ), either that or just take an educated guess at the correct position and fit needle loosley. Can you get the dash cover off with the cluster in sutu ? I cant coz the mounting tangs are broken and the cover is "stuck" on .

[Derek]

do you know the exact model of the sensor or an equivalent? If you find a datasheet you may be able to emulate it with a potentiometer or some resistors.

Without removing the sensor I can't see a number on it. It's the same as that fitted to 851/888 and 748/916, Ducati part no. 8000.53249, not that that helps much.
Assuming that the sensor itself is ok I can measure it's resistance and note the temperature, connect the meter to ground through a resistor of the same value then move the needle match the temperature.

[Derek]

Im not sure just how the needle is mounted but if it is on a tapered shaft then I would have a go at remounting it.
Why not use the original sensor , just remove from bike ,wire it up and dunk it in boiling water and set the needle to boiling point( cant remember if its celcius or farenheit ), either that or just take an educated guess at the correct position and fit needle loosley. Can you get the dash cover off with the cluster in sutu ? I cant coz the mounting tangs are broken and the cover is "stuck" on .

Yes, I think I might give it a go. It bugs me having things that don't work right.

[Mc tool]

Yeah ,my car is a jap import and the cassette player/radio ( yeah,I know but I have literally hundreds of cassettes & this is the only player ) needs a band expander for the radio so the display is reading 10mhz out, simple enough to deal with but just looking at it bugs the shit outa me.....just shove the tape in ....yay, Jason and the scorchers

[Thebenelliman]

Re your lithium battery my battery went flat and my lithium charger would not recharge it. I put an old 12v charger with a wire wound transformer on it for 1 hour then put it back on the lithium charger and it then fully recharged. Lithium batteries are strange things!

[Mc tool]

They sure are , my RC chopper battery must be recharged as soon as a drop of in power is noticed , if you run it near flat ( like trying to get it home ) its custard , yet my makita drill goes from full power to dead flat in about 15-20 seconds, can be left for over a month ( forgot about it ) and then charged successfuly .....and its had 5-6 years professional used and another 11 years home handyman use. Neiboughs dog got the chopper , bastard animal had the audacity to leap up and grab it while I was tormenting the shit out of it.

[Derek]

Re your lithium battery my battery went flat and my lithium charger would not recharge it. I put an old 12v charger with a wire wound transformer on it for 1 hour then put it back on the lithium charger and it then fully recharged. Lithium batteries are strange things!!

I did the same thing The lithium charger said "Under voltage" and did nothing and the new-fangled car/bike battery charger just flashed all it's warning lights. So I connected it to an old style car charger that I've had for 30 years or so (and it wasn't new then) after 20 minutes or so there were enough volts to get the lithium charger working. I then left it overnight on a balanced charge setting and by morning the charger said "Fully charged" at 14.4V and with all cells showing 3.67V. However there are grave warnings about deeply discharged lithium batteries and I have no idea how it well it will perform now. Time will tell.

[Mc tool]

Thing is Derek and benelliman if you guys wernt smart enough to give old faithful a go you would have had to buy a new battery , call me suspicious but I think its all part of the plan to seperate you from your hard earned.

[Thebenelliman]

I think you may be right about the batteries the charging on the bike is from a wire wound coil the same as my old charger has! The quality of lithium batteries depends on how the man in China has made it. Maybe after corona virus companies will be less willing to source manufacturing there. With the recession we all have coming we should support our own countries