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Any ideas? It generally stays roughly where it should be, but going round a corner etc it'll swing up to full, drop right down before evening out about where it should be. This has started happening direct from picking it up from the garage who had to recover it due to a failed starter motor. No idea if there's a connection there or just coincidence. They shrugged their shoulders basically when I called them about it. New-ish garage to me, but good reputation and been around for years.
Hi not quite the same symptoms but had a float sensor issue in my Passat (that's probably not quite the right words) but fuel gauge stopped working at random. It's all part of some sub assembly that goes in the tank.
Something electrical was out of whack and it was a quick reset/adjust on the diagnostic but was warned it might be an underlying component problem with the usual "cheap disposable bit inexorably attached to larger much more expensit bit" type of fix. See also VW washer hose and boot electrical connectors...
Car is long gone now but it went a year or two without further grief.
Likely the fuel sender sensor in the tank is faulty.
There should be a lot of damping in the Instrument cluster to prevent exactly this as fuel sloshes around the tank. Seeing as that is normally done via software it seems very strange that the needle now moves around where it didn't before.... If the garage disconnected the battery maybe there is some software learning going on - in which case it will sort itself out.
Unless it is an old technology gauge - wired directly to the sender unit with any damping being mechanical (in which case I would suspect the gauge rather than the sender).
Try running with the tank permanently brimmed so there's no room for the fuel to move around - that might be a sort of fix.....
There is usually a voltage stabiliser in the power supply for the gauge. If this develops a fault it will give erratic readings.
Thanks everyone. I've disconnected the battery to let the computer reset. See what happens in a bit. Twenty year old car so there's always something 🙂
Bit of an update:
Reconnected the battery just now and went for a drive. No change, It sits where it should about half-way, then It swings to full when I go left round a left corner and to empty when I go round a right-hander (pretty sure It's that way round anyway). But then, I drove past a police car so glanced at the speedo to check my speed. The speedo was at 0MPH even though I was doing around thirty. I'd been so busy looking at the fuel guage that I hadn't even noticed the speedo wasn't moving at all. Plus it was still at 0.0 MILES from resetting after connecting the battery.
Got a torch under the bonnet and noticed there is an unconnected sensor sticking out the top of the gearbox. I can see the metal prongs, Speed Sensor? Right next to the starter motor that the garage have changed...
The sensor disconnected on the gearbox is almost certainly the one that is affecting the speedo. I had the exact same thing when someone did the clutch or starter on one of my old cars (a job where the box came off anyway). Plugged back in and all working fine after for that. That might at least cure your speedo/trip fault
I bet it fixes both. My guess is that the software removes all damping from the fuel gauge when the car is stationary so you get an immediate and accurate reading when you turn it on, or after filling up, etc.
How hard are you cornering for the gauge to swing the full way? How much fuel is in the tank?
Did plugging the unplugged cable back in fix things?
I didn't plug it back in as it was dark and I couldn't find the other end. Gonna go have a look now. The garage is only 200 yards down the road, might let them plug it in just to prove it was them 🙂
Half a tank, don't have to corner hard at all, just cornering.
Yes, found the cable end dangling. Plugged it in and all is well. Popped into the garage to cover myself and just in case they remembered about something else they'd not reconnected. They blamed it on the mechanic currently on his lunch but said it should be fine now. Mistakes happen, so on with the next problem 🙂
Btw, if I'd known deactivating the speedo was just a case of unclipping a sensor I could've had a twenty year old car with about 30k on the clock... Surely everyone would be doing it if it was that easy?
Surely everyone would be doing it if it was that easy?
Well, why did you plug it back in? The answer for everyone else is probably the same!
Cos it's got about 100k on it now so not much of a selling point. A working speedo for cameras will be more useful.
So you mean to tell me when looking at buying a nice looked-after classic that "only 20k on the clock" etc means absolutely **** all? Well you live and learn.
A working speedo for cameras will be more useful.
Waze on your phone 😉