Fuel gauge and voltmeter packed up. Any clues

[Dave2000]

Dave the low level light is triggered inside the rheostat I believe. Once the float drops to reserve it closes a circuit for the warning light.

Another change, Toyota going backwards there IMO.

It does sound like a PC failure now the other parts have checked out, does your fuel gauge drop to empty when the ignition is switched off? If no then at least that still has the stepper motor system, so still needs power to go up or down, given the volt meter stopped working at the same time, your back to an earth issue, electrics p*ss me off!

Regards

Dave

 

[Chris]

The fuel gauge shows content even when ignition is off. So yes it needs current to push it up and down. I moved it with my finger to see if it would push back up even though it wasn't dropping. Nope. No movement at all.

Different earths and different plugs. Everything else that shares those earths is working perfectly so I have to suspect the power feeds via the PCB tracks. The fuel gauge, I think, gets the same voltage as the voltmeter, but the tank sender is a variable resistor so it affects the impedance in that circuit. Effectively the fuel gauge is really an ammeter? Well something like that. If neither are getting power in then there's no activity. Looks like I'll have to take the damn dash out AGAIN. Still, easier than the 12 valve.

 

[Chris]

Whooo Hoooo! Get in. Back of the net. Get the beers in.



Had dash out again and couldn't see any breaks. But looking at the little machine screws that protrude from the tracks I noticed that there was one hole with no screw in it. Now I know that sometimes there are gaps, but this one looked like something had been there originally. So I scrounged up a small screw and popped it in. Yes. That was it. Now where the little blighter had gone in the first place I can't say. But it's all working again now. You just can't kill these machines.

 

[StarCruiser]

Nice one Chris.

 

[frank rabbets]

I feel your joy Chris.

Was that screw just for an electrical connection or was it holding parts together as well ? Interested but can't quite picture it.

 

[Chris]

Well I'm not sure Frank. I noticed the copper 'polo' in the track and it looked slightly scuffed and I thought, hmm, that's not 20+ years old right there. I looked in the hole and could see a threaded brass insert down at the bottom. Now clearly this is part of the circuit but I don't know if it was also a securing stud as it were. I was so overjoyed at fixing it that I didn't honestly look any further. But the innards of the unit weren't loose at all.

 

[Dave2000]

Good find, possibly loose and the disturbance allowed it to fall out, only to be found on the floor in a few days time?

Regards

Dave

 

[frank rabbets]

Ha Ha Ha. It might cause a short circuit if loose disabling the fuel and volt gauges.

 

[StarCruiser]

The speedo occasionally went full scale so I’m guessing it dropped out the back of the speedo. There are 4 screws IIRC which both hold and make contact.

 

[clivehorridge]

Great find Chris, I hate things not working that should.

My good-for-nothing oil pressure “indicator” zero’d and still is, so I installed a proper gauge and coupled sender so I don’t miss that one.

But years ago, my fuel gauge set itself at just under half full and stayed there irrespective. So I took a flyer and got a replacement sender unit from Karl.

It worked fine (in fact more accurately than before) for about 3 weeks and then died. It reads just over half full irrespective, now.... but the low fuel light works as it should, so some comfort there.

I’ll live with it I suppose, but maybe another s/h replacement sender will happen at some stage, its more annoying than an inconvenience.... I’m guessing a new sender unit will be a small mortgage...

 

[frank rabbets]

Just use a dip stick under the rear seat Clive. lol.