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Fuel and Temperature guages stopped working!

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It's happened before when driving along, both guages will simultaneously drop to zero but seconds later spring back to normal.

Last Sunday they dropped but didn't return. Just gone for a drive to see if they would decide to work again but nothing.

Both the warning light for low fuel and the radiator fans come on as normal so that's a relief. So where can I look to see if I have a loose wire or earthing problem.

Thanks in anticipation of some guidance

Cheers

Peter

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I'd say you need to look in the binnacle, from memory those gauges (and others) are fed from a voltage regulator that is in effect just a flasher unit, staying on long enough to average out to 10v (it delivers 12v, 12v, 12v, 12v, 12v, 0v 12v, 12v, 12v etc). the connection to those gauges may have come away from it;s connectors. I'd guess at the binnacle as that's the point where they're common together but further away (binnacle supply) other gauges would be common as well.

Andy

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Check you have power going to the fuel sender unit and the temperature probe first before you start on the binnacle. If you have power then you know the fault is somewhere between the sender / probe and the gauges in the binnacle. If you don't have power then you know the fault is pre sender / probe.

It maybe something as simple as a bad ground connection in the binnacle.

Good Luck.

Gavin

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mine does exactly the same, both gauges go down and up in sync, it is a voltage regulator wire problem, probably a bad earth, its somthing else that is going on my list of things to do tomorrow (friday)


Лотос - для тех которые знают разницу

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I think it's the regulator too Peter. I remember a topic when someone opened one up and was astonished at its agricultural design. Maybe a search will find it.

I am keen to see the regulator, so Dave - progress report will be required mate, with pictures. Feel free to accidentally include great shots of your car. :(

Iain

p.s I can't find a picture of your car Peter - how did you slip that past??

Edited by iainskea

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Voltage regulator. If you look right below the binnacle on the right you will see it. Pretty easy fix on my 83.

jeff


www.espritturbo.com

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Thanks guys for the advice

So once I find the voltage regulator what do I do with it? I know it may seem a daft question but DIY isn't my strong point.

I have in the past got into the binnacle so Ill happily have a feel around in their tomorrow weather permitting.

I update you all

Thanks

Peter

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Order up a replacement. Might not look exactly like the one in your car but should include instructions on how to connect. Many british cars used them and there isn't a one size fits all in terms of connections but function is the same. I believe I removed the right panel that houses the fuel gauge for better access (left-hand drive car).

Jeff


www.espritturbo.com

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Here is the topic, on an S3 by Mark:

Iain

While trying to find out why my temp gauge was not working properly, I decided to focus on the voltage stabilizer. It is located in the binnacle, and stabilizes the voltage going to the fuel and temperature gauge. It is important to know that this is NOT a regulator. I was expecting to see a nice solid state regulator. When I opened it up, I was kind of horrified! The design is quite rudimentary! The way it works is that voltage runs through a plate to an internal contact point, where it then jumps through the contact, and goes to the 2nd plate connected to the output. The second plate is a bimetalic strip that has a coil of wire on it, which the other end of the coil goes to the stabilizers outside case. (make sure your case is properly grounded, or it wont work.

When the voltage is normal, the plate will not heat up enough to bend the strip and open the contacts. When the alternator is running strong, and your voltage rises a bit, then the coil generates sufficient heat for the strip to open the contacts, and briefly remove voltage from your fuel and temperature gauge. There is a 1 uF (250 v) capacitor across the contacts to suppress arcing and contact wear. When the strip cools sufficiently, the contacts close, then the cycle repeats. A couple of things can go wrong here. If the coil burns, then it wont work. If the capacitor is old, then it is probably dried up, and the capacitance diminishes, which could cause the contacts not to open or close properly. You can get a new capacitor from most any electronic source such as Radio Shack. Contacts also wear out. I do not know if the part is available. I would gues it is. Cant be too expensive to replace. Also, it is important to note that your gauges use the same type of bimetalic strip and coil to make the needle move. Very inaccurate IMHO. This stabilizer merely removes voltage for a period of time to your "heaters" in the gauges.

A mechanical gauge is the best option, but the sender wont fit into the water pump casting. I do not want to drill and retap. I want to keep it stock. I am putting in a new electronic gauge. Cool thing about these is that most already have an internal regulator (zener diode). Make sure that you use normal 12 vDC to power the new gauge. Do not use the stabilized voltage regulator output that the Smiths gauges utilize-it is not compatible. They dont use the bimetalic strip, and are much better! You can test an recalibrate these gauges yourself if needed with a small jewelers screwdriver and a thermometer. There is a potentiometer inside the gauge that you can get to from the back. I put my sender in a foam cup with hot water and a very accurate digital thermometer. Then I turned the potentiometer to line up the gauge with the thermometer. I tested, tested, and retested, at varying temperatures. It works perfectly!!!!!!

Also, the heat generated by the bulb while driving at night wont interfere with the reading! B)

here is a photo-sorry....it is blurry

P1010028.jpg

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I'VE FIXED IT

Removed 10 screws in order to slide the board holding the dials out and looked to the right where the temp' guage sits. There I found a loose wire with a spad clip on the end. Looked to me that it had come off something so felt around and there was a male connector pointing out of what I presume was the voltage regulator fixed right behind the temp' guage.

Put it back on, turned the ignition and the petrol guage sprang back into life. The connection was very poor (no firm click) so I added some sellotape to keep it in place. Job done!

I know it's only a tiny matter, but I'm so chuffed to have fixed it. I've had the car almost 20 years and it never lets me down. This is probably due to the golden touch Norman in Dartford has when he has replaced the two cracked manifolds I've had over the years and tinkered with other bits and bobs whlist the engine is out.

Thanks again for pointing me in the right direction.

Cheers

Peter

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Nice fix, Peter.

On a somewhat related note, many years ago I retrieved my car from my mechanic and started to leave. Noticing that the fuel gauge was reading surprisingly full, I asked whether they'd put gas in it. No. That was strange, but I drove off anyway. Minutes later, I noticed the temp gauge reading high. After getting scared, shutting the car off, checking things, and then restarting, both gauges read normal. Then, on a later date, after about 30 minutes of driving I noticed the same phenomenon: I look at the temp gauge, get scared because it's reading high, then also notice it tells me I've got a full tank when I know I've got much less.

My "regulator" has since been fixed, but it's good to know there is this electrical interaction. If you're ever in doubt about your temp gauge, you can always stop, pop the hatch, and listen whether the coolant tank is sizzling or whether coolant is coming out the overflow hose.

-Dave


All Cows Eat Grass

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