Wobbly Gauges

[Geoff Johnson]

About 6 months ago my fuel gauge started to wobble. It's ok when it is above 3/4 full, but after that any hard acceleration or bumps make the needle oscillate wildly, which is a pain when it's early on a Sunday morning, your wallet is at home & you are wondering if you have to return or can do another 20 mile loop.

Now my temperature gauge started to do the same thing, under hard acceleration it changes from its' normal just about to overheat to showing about 40 degrees. I have checked the water in the rad, just in case I was accelerating so hard that the coolant was forced away from the thermostat (I know I am probably dreaming) but that's fine.

 

The query is, am I likely to have one problem ie earthing or voltage drop, or do the coils or springs in the gauges tend to break down?

 

Is there a quick fix, or does anybody have any good idea's?

 

 

Geoff

[Alex Wong1697456877]

It's possibly the sender in the tank. These can lose their damping causing it to bounce up and down. I'm not sure if it's a mechanical or electrical failing but I've had this problem before. Replacing it is easy enough. The sight of that rheostat sitting in the petrol tank always makes me nervous though!

 

Alex

 

Edited by - Alex Wong on 4 Sep 2000 14:41:09

[Peter Mears]

Turn on the heated front screen and the oil pressure drops and the temp rises. Solution: Don't turn it on. Anyway could be earth problems.

[Julian Thrussell]

If it were just the fuel gauge I would say check the sender in the tank, try removing the sender (float and all) and putting it back perhaps in a different position. You can often turn the unit in the in the tank by using the location screws. The fuel slosh may be putting pressure on the resistor in the sender unit.

 

Because you now have two doing the same thing.....check the wiring connectors are all clicked home, put your hand behind the dash and move the wires around looking at the instruments.

 

If it carries on, get some spare instruments and plug them in, just dangling under the dash is ok. If they do the same, connect them directly to the relevant senders and see what happens. Work back to the source.

 

[Simos]

 

Most electrical problems are the earth points, on my 91 there are two chassis earthstraps connected to the top left bellhousing bolt, one under the dashboard left side and one at the left rear of the car inside the wheel arch. Taking all these apart, bit of emery cloth and put back together will solve all manner of gremlins.

 

I've also had a not dissimilar problem when my alternator died. The rectifiers got toasted and would charge (red charge light went out) between 2.5 - 3.5k revs or anytime under fierce acceleration. Failure of either would reset my instrumentation. Another thing to check is the alternator cabling which gets toasted if it's under the headers as normal. Give them a wiggle to make sure they're ok.

 

Cheers, Simon.

[Asklepios]

Almost certainly an earth.Similar problem suffered close to wiper motor common earth,which on first inspection was"clean",but had an aluminium washer fitted which needed burnishing then replacing.

[Geoff Johnson]

Thanks for your assistance. Looks like I have a painful afternoon contorted under the dash in the near future. Might as well but the footwell mats back in at the same time.

 

I will let you know what I find

 

Geoff

[Steve W]

I had a similar problem. Temp guage would go up until you flicked the heated screen on and off a couple of time. Problem as suggested was the earth on the wiper motor. Make sure you rub back some of the power coating to get a good earth.

 

 

[CHRIS CLARK]

I have a fuel gauge that doubles as a suspension/road bumpiness gauge! It is a VDO unit that has lost its damping. I have spoken to VDO direct and they can rebuild the gauge for 20 UK pounds to reinstate the damping.