Car advice

[fireheart]

OK, my car is a 95 Ford Laser Station wagon. Automatic transmission. Works perfectly fine barring two things:

1) the aircon switch is broken (which we're fixing)

2) the problem which I'm about to put up here.

Because my car has a cassette player and not a CD player, my boyfriend gave me his old iPod transmitter so I could play my iPod in the car. Said transmitter plugs into the cigarette lighter, then has the unit which is set to a radio frequency and then plugs into my iPod. If I have it set up, but it's NOT running, it charges the iPod.

When I had it charging the other way on my way from my house to out near Nyoibo's way, the fuel gauge went REALLY funny. It dropped from F to E pretty damn quick, even though I KNEW I had a semi-full tank of petrol in there. Whenever I braked or was climbing up a hill, it would climb up a bit, sitting somewhere around the 1/3 mark (my tank was 2/3 full and the fuel economy on my car is 9L/100km) but afterwards would drop back down to E. I spoke to dad, who said it was normal for the gauge to swing a little bit, but not from nearly F to E pretty damn quick.

We filled it up on the weekend to eliminate a fuel leak and my boyfriend and I also learned about how the fuel sensor works. Driving it BACK home and doing a short trip today, the fuel gauge read fine (this was without said transmitter plugged in)

My question is: What could have caused the fuel gauge to go funny like that? What needs to be fixed?

[teh_blumchenkinder]

if it has a floater for the gauge reading in the tank, it might be the floater sticking. I've asked my Dad about other cars that did that, and he suggested that. I'd keep gas numbers from here on in if I were you. Just in case.

[Mikkel]

Something wrong in the electric system. I had an old car once where both the temperature and fuel gauge would suddenly swing down to zero and then back again. No one ever found out what was wrong.

[fireheart]

if it has a floater for the gauge reading in the tank, it might be the floater sticking. I've asked my Dad about other cars that did that, and he suggested that. I'd keep gas numbers from here on in if I were you. Just in case.

Yeah I'm going to test that at some point to eliminate that out. But we worked out that where it started swinging down to zero, I had about 30L left.

Mikkel, one of my exes suggested just that, so I'm going to be contacting some auto electricians.

[wolfie]

Temperature AND fuel level going wonky at the same time sounds like a voltage regulator.

As for the OP's fuel gauge, is it a "vampire" gauge (stays put when the car is shut off), or does it drop to "E" when the car is shut off? I can see 3 possible problems if it's a "fall to E", with a 4th for "vampire" gauges:

1. Voltage regulator. Would affect temperature gauge at the same time, more likely to affect the "fall to E" gauges. This is (usually) a plug-in component (fairly cheap to replace).

2. Fuel sending unit float is sticking. Unless there's access under the rear seat (check for a "mystery" panel bolted on when you've got the seat pan flipped up but not the seat back folded down), you'd need to remove and re-install the fuel tank to fix it. Expensive - and may as well get the fuel filter, (in-tank) strainer, and fuel pump replaced at the same time (since all of them require removing and re-installing the tank).

3. Variable resistor on sending unit is wonky. Same issues as #2.

4. ("vampire" gauges only) Something in the instrument cluster (either the servomotor in the gauge, or the circuit driving it) is wonky. This can be very expensive to repair (probably need a new instrument cluster).

[Seshat]

Climbing or going down a hill, or being slanted on a particularly funky road, can tilt the fuel in the tank away from (or towards) the floater, thus causing it to rise or lower. Your only totally accurate reading from the fuel tank floater is on flat ground.

Sudden acceleration or deceleration can also temporarily cause the fuel to be towards/away from the floater.

This is what explains the hill climbing/braking changes in your gauge reading.

If (other than these sensor glitches) it only goes wrong when you're charging the iPod, I'd say that the iPod is draining more charge from the instrument panel circuit than the panel is designed for.

Check with an autoelectrician.

[fireheart]

Temperature AND fuel level going wonky at the same time sounds like a voltage regulator.

As for the OP's fuel gauge, is it a "vampire" gauge (stays put when the car is shut off), or does it drop to "E" when the car is shut off? I can see 3 possible problems if it's a "fall to E", with a 4th for "vampire" gauges:

1. Voltage regulator. Would affect temperature gauge at the same time, more likely to affect the "fall to E" gauges. This is (usually) a plug-in component (fairly cheap to replace).

2. Fuel sending unit float is sticking. Unless there's access under the rear seat (check for a "mystery" panel bolted on when you've got the seat pan flipped up but not the seat back folded down), you'd need to remove and re-install the fuel tank to fix it. Expensive - and may as well get the fuel filter, (in-tank) strainer, and fuel pump replaced at the same time (since all of them require removing and re-installing the tank).

3. Variable resistor on sending unit is wonky. Same issues as #2.

4. ("vampire" gauges only) Something in the instrument cluster (either the servomotor in the gauge, or the circuit driving it) is wonky. This can be very expensive to repair (probably need a new instrument cluster).

Not the temperature gauge. Just the fuel gauge. Mine is also a drop to E gauge.

I plan on testing out theories 2 and 3, to see if it's a sticky sensor. So far it's been reading normal. I'll post up my test results soon.

[Chromatix]

The cigarette lighter socket is designed to power a cigarette lighter - basically a small heater. There is no reason why an iPod should exceed that power drain. I suspect that the iPod is a red herring here.

There's an easy test: next time it happens, unplug the iPod. If the gauge doesn't immediately recover, the iPod isn't the problem.

Old Volvos have a common problem where the fuel gauge in particular would read intermittently or not at all after about a decade or two of driving. This is because the wiring loom which carries these signals was routed past a hot corner of the engine, and this slowly degraded the insulation. Replacing the wiring loom (fairly expensive) and then protecting it from the engine is the cure.

[fireheart]

OK, a few updates on that.

1) I've been running the car sans iPod for about a week now. No problems at all, barring the fact that it sometimes takes a while for the fuel gauge to read correctly when I start the car.
2) We've worked out that it's DEFINITELY something to do with one of the electric parts.

Also, one more thing to add: even without the iPod plugged in, the gauge wouldn't reset until AFTER I filled my car up.

[fireheart]

Bumping for an update.

So I took it out today because I needed to go bra shopping (and I swear that every woman within my area must be an E cup because there were very few 16E bras) and it did it again when I was heading down a hill.

Went and filled up-only needed 13L before it clicked off. Tested to see if it was a gravity issue on the way home by driving along some VERY steep hills, even more steep than the one I went down on today. It's not, the fuel gauge didn't budge from full after I filled it up.

My theory right now is that the fuel sensor is stuck-once it drops below that point, then it thinks that there's nothing there. In short, looks like another loan to pay for the costs to fix it >_<

[Imprl59]

Most likely the sending unit in the gas tank as others have already suggested I just wanted to add that it isn't likely to cause any other issues. If you don't want to have it fixed right away just use the trip odometer to keep track of how many miles you have on a tank and fill up well before it "should" be empty.

I don't know that model car but many of that era and later have the fuel pump and sending unit all built together as one piece so it can be a bit pricey to swap out.

[fireheart]

Most likely the sending unit in the gas tank as others have already suggested I just wanted to add that it isn't likely to cause any other issues. If you don't want to have it fixed right away just use the trip odometer to keep track of how many miles you have on a tank and fill up well before it "should" be empty.

I don't know that model car but many of that era and later have the fuel pump and sending unit all built together as one piece so it can be a bit pricey to swap out.

Yeah I'm starting to think that's it. I'm going to get our neighbour friend of mine who works in roadside assistance to check it out fully and recommend a good mechanic.

as for cost, I'm going to see what dad says. Hopefully we might be able to go halves on the cost.

[fireheart]

Bumping for update!

So dad managed to track down a sender unit AND the workshop manual for my car (not to be confused with the manual that you get when you buy your car). The former from a wreckers, the latter from your friendly neighbourhood library. And I learned a fun little factoid: my car is actually 94, not 95 despite what it says on the certificate. Furthermore, the model that they made is unique. My sister's car is the same, hers is a KE, while mine's a KE2.
And to make things even more interesting, they stopped making the KE models in 1990, but continued to make the wagon (which I have) up until 95. So my dad just used the KE book.

We're going to test it out this week.

[Jester]

I actually have a unique perspective on this situation, having lived with it for a few years now.

When I bought the current Jestermobile 5 years ago, everything seemed fine. Drove it off the lot with a full tank of gas. Yet 3 weeks and about 120 miles later, the gauge still read full.

So I gassed up, and sure enough, ended up pumping quite a few gallons into the tank. I called the dealership, but they claimed not to have known about the gauge not working when they had it, saying that the previous owner had, to their knowledge, left it with a full tank of gas. Since the gauge was reading full, I can understand their oversight. Sadly, since I bought the truck "as is," it was now my problem, not theirs.

I consulted with my mechanic, a guy I trust. After looking at it, he determined something was wrong with the gauge itself, rather than the floater, and that I would probably have to replace the entire instrument panel to fix the problem, a replacement that would cost over $600. Fuck that!

I had one advantage, though. This Jestermobile was the same make and model as the previous Jestermobile, albeit 11 years newer. I figured they probably got similar gas mileage. So I started using the trip odometer as my gas gauge, gassing up at X miles when in town, and Y miles when driving highway. And I was pretty spot on. The downside to this system is that it only works if you fill up every time--otherwise you won't have a good idea how much gas you have. The upside to filling up all the time is I stop far less often at the gas station!

Over the last five years, I have noticed the gauge occasionally bouncing around, sometimes reading F, sometimes dropping to E, never being in the middle. But I haven't needed it, as the trip odometer has worked just fine. And honestly, I have run out of gas far less in this truck than in previous vehicles, as I have not been doing what we all do, trying to get as much past E as we can before stopping for more gas.

Other than the gauge, and a couple of other minor problems, I couldn't be happier with my truck, and don't know that I'll ever really trust a gas gauge as much as the trip odo. It seems to work better for me!

[fireheart]

Yeah, I've used the tripmeter so I can keep track, especially if I'm doing extra travel during the week.

Although I have a new conundrum for everyone....my air conditioner on my car will only work if I put it onto the full blast switch. It will not work on lower settings AT ALL. Any ideas?