Newbie temp guage problem

Hello all
im a newbie with my newly purchased 90' clipper, the temp guage didn't seem to be working so my mechanic put in a new sender but now the guage rockets up to maximum within 10 mins! It doesn't seem to be over heating, there's water in the expansion tank/bottle and the heater blows very hot air! Any ideas? I'm sure this has been asked many times but I'm new to the forum.
Im taking it back to my mechanic tomorrow, any hints/help for him?
many thanks

rog

Hi and welcome to the club :-)
Sounds like the wrong sender has been fitted. The sender is a simple device that alters its electrical resistance as it heats up. I lifted this from a Rubjonny response off Club GTI - he posts on here a lot as well :-)

From the haynes manual, resistance values for 049 919 501 A, 027 919 501 and 049 919 501:
20°C - approximately 1000 ohms
60°C - approximately 250 ohms
100°C - approximately 75 ohms

Thanks for your welcome and reply, how do I make sure he's ordering the correct one? Is that the Haynes info in your msg?
Rog

No worries.
Yea, it should have a black top and allow a temp reading  of 0 to 125 degrees.
Get a genuine VW one as the after market ones are usually crap :-)

Thanks again Ade
I'll check and get a new one sorted, I guess that means the reading I'm getting is incorrect then and I'm ok to drive for the moment?

Rog

It does sound like it is ok to continue to use. You could always take it to a garage as get them to use an infra red heat gun to check the actual temperature.


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Just so you know these critters get up to temp quick.
The normal is at half deflection to 3/4 deflection.

When running it will usually be about 1/2 and on stop climb a bit.  Normal.

Thanks Ade, new sender 1st I think, will I be able to establish if the part he's put in is the wrong one? Other than a black top?
Rog

If it is genuine VW then it will have the part number stamped on it.

If you have a multimeter you could always check its resistance in cold water and then boiling water against the resistance measurements given earlier.


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Thanks briano but the guage virtually rockets straight up off the scale and doesn't move at all

Rockets straight up when you turn the car on or running?  
Is the fuel gauge doing the same?

The fuel gauge and the Water gauge both need a good 10V stabilized voltage in the cluster.

If the Sending unit is bad, that is cheap and easy to replace.  First thing I think of.  Using a DVOM (digital volt ohm meter) you can test it very quickly.

Mis-matching a t-stat to the radiator switch is quite a common thing to do by accident.

Not having a upper radiator card as well as obstruction on the fan shrouds flapper valves is another.

These critters do tend to get up to temp rather quickly.
But they should run mid deflection to slight to the right, and then again at 3/4 to almost the red line the Fan should kick on.

With the advent of parts stores getting more and more parts from "Made in China" I have seen more than one Failure of items either right out of the box, or a couple of weeks later.  

Change the sender, and then we can see if you still have to investigate or repair.

Dodger said

Thanks briano but the guage virtually rockets straight up off the scale and doesn't move at all

I had a few issues previously with the temp gauge on my GTI. It started sitting very low even when up to temp. I was told to check the gauge by earthing the wire that goes to the sender on the head. This as it did put the temp needle to full which meant the gauge was ok. Purchased a new sender, febi one and had a similar issue as you are having that the temp gauge would go up to 3/4 nearly all the way when up to temp. Mine always before the old sensor failed sat half way. Requested a replacement, swapped over and it was all back to normal so from experience I suspect it could just be a faulty new sender. Like briano suggested, just as it a new part, don't always assume it works or works correctly. 

Hello again, new sender (from VW heritage) and the guage hovvers nicely in the 'low zone'  (what seems to be an accurate reading)
Thanks Ade/all

Dodger