Fluttering Fuel and Coolant Temperatute guages

[DavidOliver]

For the third tme I have taken the dashboard down to try and find the Voltage Stabiliser as shown on Wiring diagrams.
The reason is to stop guage fluttering and a periodically ticking noise behind the dash.
For the third time I found NO such thingeme. Nor did I find any strange surgery to the wiring, which was in very good state.
Not wanting to install new guages, and not thrilled with installing a mechanical/electrical stabiliser where apparently
there has not been one, I ask Forumers what is their experience and is there an electronic device which can do the job?

As an aside, for Gear Knob readers, obviously the Anti roll bar comment was a Deliberate mistake, tell that to the Marines.

Dave the cog.

[richardw]

Dave, do you have Smiths instruments? If so, I'm pretty certain the voltage stabiliser is the same as fitted to other British cars with Smiths gauges. It is a metal unit that should be fixed to the back of one of your instruments - mine is. Here is a link to a page that shows what it looks like and how to upgrade it to a more modern unit: http://www.britishv8.org/Articles/MGB-V ... ilizer.htm

Good luck, Richard

[Lotus-e-Clan]

I think you have reported this before elsewhere IIRC but I can't remember the detail so please forgive if I ask dumb questions and make dumb suggestions...

?IF VDO instruments:

The fuel gauge wobble is usually caused by the inherent lack of sensor damping. If your fuel light also flickers/fluctuates too then it's likely to be caused by the normal sensor damping issue. There is an electronic damper fix for this. I have used one for years and it works for both gauge and fuel light....no wobblies.

VDO gauges don't need an external voltage stabiliser... but, because the VDO sensors operate by 'sinking to earth' the gauge sensor lead, intermittent sensor / engine earthing (sensor wire or engine earth issues) will cause intermittent gauge readings.
Water sensor earth issues aren't reported as often as oil pressure sensor earthing issues. When the oil pressure sensor wiring connection is poor, you usually get a step change in pressure for no reason. The pressure will read high when wire resistance increases due to a poor connection...if you remove the sensor connection the gauge will read maximum.

In theory the water sensor should operate the opposite way because heat lowers resistance. So unlike the oil pressure sensor (high resistance = high reading) , decreasing resistance gives high gauge readings. If you have a temp sensor wire resistance issue the the needle will tend to drop due to a fault rather than rise as is the case for oil pressure. Have you wobbled the water sensor wiring (when up to temp) to see if the reading fluctuates?

Apart from the well-reported servo valve tick, - under-dash ticking is more often due to relays opening and closing. I don't know if there is a dash-associated relay (can't look atm) but I wouldn't be surprised if there is one and it's faulty.

[Mr Locust]

a periodically ticking noise behind the dash

Intermittent wiper relay unit?

[pompey ice]

Hi Dave , It all boils down to what gauges are fitted if they are smiths then change the regulator is a must
either your original is missing or its been replaced by an electronic one that is now faulty ,the one in the pics
is the original box with upgrades installed ,when i had to change mine there were several on the market [ebay]
that came in either version they all specified a constant 10 volts output to the temp and fuel gauges ,trace the wires
back from the dials to source as mentioned [ its on the back I seem to remember one of the large dials ]
as for the ticking could be something completely different

Cheers Ian

[hodders]

Surely the most likely cause of a ticking behind the dash is the speedo cable on the way out?

[Phantasm]

My otter switch makes my fan relay chatter when it hits the temperature at which the fans kick on -not sure why exactly and don't fully understand the inner workings of an otter switch. But, when my engine is right in that 'sweet spot' of just getting too warm but the radiator is easily able to keep up and cool it down quickly, I hear it chatter a lot as the fans get fired up. THis tends to occur typically at stop lights after bolting around for half an hour or more. That might be what you are hearing? For me, it sounds like it's coming from the dash binnacle but it's just off to the right in the relay harness. I've verified this with the 'feel' method. I can feel the relay chatter as the fans kick on. I suspect the Otter switch, what ever it does internally, is not sending quite enough current to keep the relay open at first until it really gets 'hot enough' then holds it open to keep the fans engaged.

The fuel gauge: if you have OEM-like equipment it responds immediately to fuel movement in the tank, which occurs a lot in a transverse mounted tank. Thus it dances around the corners. There are many ways to install a smoothing device to combat the effect. Some have put in a electric smoothing box -forget the brand they use, it's on the forums here- in the wiring harness between gauge and sender. I changed out my sender for a diptube style. Works great, no moving parts, but I got the resistance measurements wrong so my gauge reads full the first half a tank than quickly drops off the latter half. The low fuel comes on at 10% tank but looks like 1/4 on the gauge (VDO). I reset my trip meter and am always pretty aware of my fuel situation without risk of running out. Having the low fuel light work was of utmost importance to me.
Link to the install to increase my view count!!!
https://www.youtube.com/watch?v=bUKfTwYITxs

[Pete Boole]

Pretty sure the Otter switch is just a bimetal strip - maybe the contacts are pitted?

Pete

[DavidOliver]

My car has VDO guages and I am now sure there was originally no Voltage stabiliser.
Anyway I installed a new stabiliser across the water temp. and fuel guages.
I then found the cable connector to the water temp. sender, a simple bayonet type clip, to be loose so I nipped it up.
I also put 30-odd litres of fuel in the tank.
I now have no flutter on the temp. guage and the fuel is much more stable.
I conclude that the stabiliser is not needed so I will remove it.

The ticking noise behind the dash is still there, periodically, and occurs with the car stationary and no windscreen wiper on.
The battery is brand new.
Perhaps my Tachometer is a Tickometer.
I can´t hear any ticks at speed, not surprising with my exhaust note.

Dave the cog.