temp gauge testing

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type53b
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temp gauge testing

Postby type53b » Fri Mar 10, 2017 12:00 am

My car seems to run a bit hot at the moment. The gauge is sitting about 3/4 of the way up after about 20 minutes driving but I am not fully convinced it is overheating. I fitted a new gti rad, flushed the cooling system, filled it up with g12 and as far as I can tell I bled it correctly. It doesn't lose or leak coolant. The level never varies. There is no oil in the coolant tank. Could it be, that she is at normal temperature but the gauge is reading high? If so how do I test the gauge and sensor ?


remember, if it's got tit's or tyre's, sooner or later it's gonna give you trouble.

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scrappy1382
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Re: temp gauge testing

Postby scrappy1382 » Fri Mar 10, 2017 1:57 am

hi matey, there is a alternative to your problem if you wish for your fan to cut in earlier ?

1 you can buy a thermostat with a lower open/close temp
2 a earlier temp switch rigged into your cooling system that allows your fan/fans to kick in earlier.

my storm always had weird temp readings including the oil.

i will send over the link to the earlier fan switch system

http://www.ebay.co.uk/itm/Mishimoto-Adjustable-12V-Car-Engine-Cooling-Fan-Controller-Kit-Probe-Sensor-/311709346397?hash=item4893532a5d:g:TIQAAOSwpLNX7gUC

something like this


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mark1gls
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Re: temp gauge testing

Postby mark1gls » Fri Mar 10, 2017 11:58 pm

The sender should have writing on the side with the temperature range on it, what does it say?

The gauge should sit at 1/2, when stuck in traffic rise to 3/4 then fan kicks in and lowers it back to 1/2.

Is your bottom radiator hose getting hot?

Try starting the car with the expansion tank cap off and see if there is a flow of coolant into the tank from the thin hose, it should increase the flow if the revs are increased.

What colour expansion tank cap do you have? If it's black change it for a blue one, you can have problems with the black caps.


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ThomasD
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Re: temp gauge testing

Postby ThomasD » Sat Mar 11, 2017 1:04 am

type53b wrote:My car seems to run a bit hot at the moment. The gauge is sitting about 3/4 of the way up after about 20 minutes driving but I am not fully convinced it is overheating. I fitted a new gti rad, flushed the cooling system, filled it up with g12 and as far as I can tell I bled it correctly. It doesn't lose or leak coolant. The level never varies. There is no oil in the coolant tank. Could it be, that she is at normal temperature but the gauge is reading high? If so how do I test the gauge and sensor ?


The gauge can be tested. If you disconnect the wire at the sensor, and connect the wire to earth through a variable resistor, here is what you should see:
With a resistance of 40 ohms, you should be at the full hot side of the gauge.
With a resistance of 258 ohms you should be at the full cold side.
The service manual allows for one needle width of deviation from full hot or full code with these resistances.
These measurements are made with the engine running.

VW has a simple tester for this, but you can use also use a variable resistor or potentiometer. That being said, I'd be surprised if the gauge it bad. I think it would be more common for the gauge to not work at all. I'm not sure if the senders themselves go bad - again I would sort of think if they fail, they fail altogether. The service manual says if the gauge is good, but your reading is bad, replace the sender.


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type53b
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Re: temp gauge testing

Postby type53b » Sat Mar 11, 2017 10:17 pm

Hi all, thank you for all the advice. I have figured out that the engine is running at normal temperature but the gauge is reading high. I done this by unplugging the wire off the oil temp sender at the top of the oil filter housing and connecting it to the water Temp sender and then reading the temp off the oil temp clock above the radio. I gave the car a good blast for 20 mins and it held steady at 90 degrees on the oil temp clock but read 3/4 on the water clock. I then left it idling for half an hour and the temp climbed up to 100 degrees on the oil clock, then the fan kicked in and dropped it back to 90. I kept swopping the wires back and forward to see what each gauge was reading and it stayed the same , oil gauge said 90 , water gauge said 3/4. The oil gauge read 100 ,the water gauge was nearly all the way to the top and the fan cut in every time and cooled her down to 90. Thank god!!! So the water gauge must be bogey.


remember, if it's got tit's or tyre's, sooner or later it's gonna give you trouble.

mark1gls
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Re: temp gauge testing

Postby mark1gls » Sun Mar 12, 2017 12:52 am

Could be you have the wrong sensor fitted there is a couple of types which look the same but have different readings-operating ranges.
What's on the side of your sender?


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type53b
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Re: temp gauge testing

Postby type53b » Sun Mar 12, 2017 11:14 pm

I will have to check tomorrow when I am back in work. The car is stored in a shed there. Should there be a temp range stamped on it?


remember, if it's got tit's or tyre's, sooner or later it's gonna give you trouble.

mark1gls
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Re: temp gauge testing

Postby mark1gls » Sun Mar 12, 2017 11:53 pm

Yes there should be a stamp on it if it's a VW one, may not if aftermarket one. I think it should say 120 on it but I will check mine tomorrow to see what's stamped on mine.


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Mk1 78 Scirocco GLS 1.6 FR, weekend toy.
Mk1 88 Golf GTi cabriolet 1.8 DX. Daily drive.
Membership No. 323

type53b
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Re: temp gauge testing

Postby type53b » Mon Mar 13, 2017 1:56 am

Ok thanks mate!


remember, if it's got tit's or tyre's, sooner or later it's gonna give you trouble.

mk2daz
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Re: temp gauge testing

Postby mk2daz » Tue Mar 14, 2017 9:40 am

Take out the temp gauge sender plug, bridge the two pins on the plug together with a jumper wire then turn ignition on, if gauge goes to max then your gauge is working fine and it's most likely an incorrect sensor as has been said above :)


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type53b
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Re: temp gauge testing

Postby type53b » Wed Mar 15, 2017 5:49 pm

I don't have a 2 pin connection on the temp gauge sender. It is just the single nail head connection with one spade terminal slid onto it. I already took this off and grounded it off the engine block and the needle went straight to the top of the gauge. Is this the same thing???


remember, if it's got tit's or tyre's, sooner or later it's gonna give you trouble.

mark1gls
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Re: temp gauge testing

Postby mark1gls » Wed Mar 15, 2017 9:06 pm

My VW sensor has 12v and 125 written on it, it does have a part number but it's at the back near the head and I can't really read it!


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Mk1 78 Scirocco GLS 1.6 FR, weekend toy.
Mk1 88 Golf GTi cabriolet 1.8 DX. Daily drive.
Membership No. 323

mark1gls
Posts: 2385
Joined: Thu Apr 02, 2009 9:28 pm
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Re: temp gauge testing

Postby mark1gls » Wed Mar 15, 2017 9:12 pm



ImageImage
Mk1 78 Scirocco GLS 1.6 FR, weekend toy.
Mk1 88 Golf GTi cabriolet 1.8 DX. Daily drive.
Membership No. 323

type53b
Posts: 139
Joined: Tue Jul 07, 2009 11:12 pm
fill in the right answer: 10
Location: ireland

Re: temp gauge testing

Postby type53b » Wed Mar 15, 2017 10:09 pm

I can't decipher what is written on mine . I think I will have to remove it and clean it up to figure it out.


remember, if it's got tit's or tyre's, sooner or later it's gonna give you trouble.


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