I'm sure this will have been discussed, but I can't find a thread on it. Our fuel gauge is great when the van is stationary. Seems to fairly accurately estimate the amount of petrol in the tank (as long as the lights aren't on, if they are we get another quarter tank). However, as soon as we're driving the needle is wildly waving back and forth regardless of how much fuel we have. Not too much of a problem as I can check the gauge when we stop, but it is annoying. Is there any physical dampening of the fuel gauge needle, that might have failed, fallen off, etc.? Or is it more likely to be an electrical issue? Maybe something up with the sender unit? Its been like this for at least the last five years. Thanks
Yes, they are damped. Has it got a grey face (early) or black face (late)? Earlies are damped by the plunger type sender, lates by the gauge itself.
The gauge damping effect comes from two sources. First the hot wire in the meter which stops the needle moving too fast, and then the voltage regulator. This ensures you get a constant 5.2volts or thereabouts so damps out the effect of the alternator running at different speeds.
If its post 1973 . Most likely you have a birds nest of broken resistance wire in the sender and it's about to give up forever. Pre 1973 loose connection in the tube type sender..
Could be the sender. The damping on the later gauges comes from the bi-metallic strip that moves the needle. They are very heavily damped. If the gauge moves rapidly back and forth, implies it's an early, moving coil job.
Thanks all. It is a 73, but the whole dashboard is from an early. According to some hand written notes that came with it, a PO replaced the sender at some point, maybe ten years back, no idea to which type. From recollection, I don't think there is a voltage regulator on the back of the dial cluster. So really could be anything, or a combination of them all... Seems like a good excuse to fit a sender inspection hatch, I've got the kit to do it, but haven't got around to it yet.
Ha! Exactly. Connect an early gauge to a late sender, and it'll be all over the place, as there's no damping as the fuel slops around. Symptoms as described above.
Thanks again. Only one way to find out, I'll fit the little inspection hatch, and see what we find. Knowing our garage, most likely mice...
@Mr Apollo, I've seen one of these on an early style guage where the 6mm tab on the back of the gauge had come loose from the gauge's internals, causing an intermittent connection, it was probably due to the weight of the wire over the years pulling on the tab and could have been exacerbated by road vibration. The result on the needle was something like you describe. Check the back of the gauge before you go cutting an inspection hatch.
Now that I've established that I have a late sender, and an early fuel gauge, I need to figure out the best way of ending up with a relatively stable gauge needle. Looking at the early senders online, I suspect they wouldn't fit the current tank, do they twist in like the later senders, or do they somehow bolt in place? Alternatively, would a late fuel gauge be a direct swap for the early one I have? Or, best case scenario, would fitting a voltage stabiliser to the gauge sort it? Having seen how much fuel is in the tank, when completely stationary, the fuel gauge seems pretty accurate.
Unfortunately, there's no ideal solution. I would go with trying to fit an early sender in the tank (they seem to be the only ones available). I suspect they're bolted in - sure someone will correct me if I'm wrong. Fitting a late gauge is a bit of a non-starter - will it fit, can you find one? They're like hen's teeth. The voltage stabiliser won't do anything: it's the gauge itself that provides the damping. Fit an early sender? Or, find a used late bay instrument pod, or fit an aftermarket VDO gauge under the dash? From memory, the aftermarket VDOs will match the late sender if you pick the right one.
A PO must have replaced the whole dashboard cluster, I've got the lighter grey inner circle, actually prefer the look, if that isn't heresy. Even have miles, plus trip miles, and a clock that runs at twice the speed it should (it is a 12v clock). I've put a km stick-on dial to meet Swiss rules. The dash is held in place by two bits of some sort of plastic that look like they once were part of a kitchen unit. I need to get some proper clips.
I had the same when I got my van, it’s a case of swapping the tank or the instrument cluster I swapped the cluster, you will have to swap the whole lot as the backing plate is different although the black plastic bit can be kept.
Umm, thanks, looks like I'll be keeping the crazy dial for a while longer then. If I figure out which direction the arm of the fuel sender is facing, I could use the fuel gauge to indicate in which direction I was turning. So the fuel sloshes to the right when I turn left, so the voltage will either go up, or down, making the gauge indicate more or less petrol. Once I've figure out which is which, it would be useful in a peasouper; if I can't see the road, at least I'll know which way I'm turning. With one of those floating compasses you used to be able to get, I'd be able to figure out exactly where I was, although I might need a sextant as well.
Good idea, it points left. I don't think one would be able to safely seal an early sender into a tank made for a late sender. I'm surprised Mike James hasn't contributed a damping circuit, perhaps he's thinking about it.
You may joke, but on a working setup the gauge will show more fuel when you're going uphill, and less going downhill (or possibly the other way round). A classic design! Keep your eye out for a late dash pod on eBay (with a working gauge). They do pop up from time to time.
