Erratic temp gauge ?

Temp gauge needle starting to sort of flutter ever so slightly..sort of like slightly vibrating....had to look at it closely to make sure I was seeing what I was seeing so it was only slight
then it became more erratic after a couple of hours where it was fluctuating about 3mm each way...eventually seemed to bounce and then just stayed right down the bottom as though the needle had just come off...but it hadn't and stayed there...checked all connections at sender etc ...all seemed good...now today it is working again and sitting just above the half way mark...previously it was sitting just below the half way mark before the fluctuations....no fluctuations now

When I did the head , the one thing I didn't replace was the temp sender ...I don't know why ?..I did every thing else !

The return pipe under the radiator cap to the overflow bottle is crimped about half way as I posted in a previous thread...I will eventually be putting a dedicated temp gauge in but in the mean time..would this be electrical , ? the sender ? or a possible a conscequence of the crimped return line ?....
From start of fluctuation to it ending up at the bottom and staying there was travelling over about 300klm constant....cheers

Erratic temp gauge on what??????

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Originally Posted by threedogs

Erratic temp gauge on what??????

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On his banana

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Originally Posted by Clunk

On his banana

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Thanks , no idea now lol

4.2 efi qg

Check that the connector at the sender is OK (Yellow, red wire). If that is okay, check the wiring harness at the back of the gauge cluster.

The resistance reading for my RB30 sender with the wire off, is 500 ohms cold and around 34 ohms at about a third way up the temp scale.

With the car running and the multimeter on volts and the wire connected it should be a constant voltage signal that drops as the engine warms up.

The photo shows the Temp sender wire (Yellow red) and the sender input terminal behind the gauge. I made a 70 cm test lead by stripping the ends of the wire and inserting one end under the input terminal (make sure no copper is touching any other terminals).

I taped the wire to the positive multimeter alligator clip and connected the negative to earth. With the meter set on volts, get an assistant to drive and see if the signal is erratic as the car bounces around. If the signal is steady, and no other gauges are flucuating it will be a faulty gauge.

The black earth wire that supplies the temp and speedo is directly under the Yellow red wire at the connector.

what is it with GQs and gauges failing all the time,
Also check the plastic fan they WILL perish and better to
replace now than later on out bush if it fails

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Originally Posted by threedogs

what is it with GQs and gauges failing all the time,

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Twenty odd years of being abused will do that to any vehicle. Has the ecm reset itself yet, TD?

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what is it with GQs and gauges failing all the time

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They aren't getting any newer mate. I didn't realise it had been diagnosed as a faulty cluster anyway?

I suppose it wouldn't hurt to check the resistance of the earth as well. I measured the current on a TB42E gauge at half temp, just out of curiosity, and it was around 100 milli amps.

Mine use to do that a lot now it works fine all on its little own.

I did fit a digital temp guage about a year ago and now I never look at the analog one.

cheers all