Temperature Gauge Reads Maximum??

I have recently purchase a Mk1 Golf GTI cabby 1.8 1984, and have a few niggly things that need sorting, firstly the temperature gauge was working fine until i noticed the connector on the sender unit (on the spark plug side of the engine) was only connected by about one strand of wire and while pulling it, broke it, so i soldered it back and now it instantly reads max and the red light flashes?? I have just replaced the sender unit and it is the same, when disconnected it falls to cold…..
Any ideas??????, the engine warms up okay and fan cuts in okay, etc, etc…
Cheers.

Just been fiddling under the lid again and whilst wiggling a few wires, i am reckoning the two wires at the lower n/s of the rad the gauge seems to work okay now, what are these two wires please? I will take it for a spin and see how it all looks.......

That sounds like the switch for the electric cooling fan. but i could be wrong.

Cheers
Steve

…. yes i think your right, cheers Steve -  it has packed up again though, so it wasn't that, i am guessing a loose wire somewhere??? Will delve deeper, any suggestions?
Cheers,
Steve

symptoms you describe sound liek a short to earth fault, think you'll have to delve deeper into your wiring loom to trace where the red/yel wire is shorted.  also check behind the dash, the red/yel wire runs to relay 42 or 43 above the fusebox if you have a level warning sensor in the header tank, perhaps the fault is here.

Cheers John, it turns out the number 43 relay is indeed completely corroded see here - http://www.flickr.com/photos/steviobee/4026458994
and i am guessing this is the problem? I do indeed have a level sensor, i am guessing again this is the VDO thing and two wire plug on the header tank.
Now to find a number 43 relay……
The relay plugs in next to number 33 at the top see here - http://www.flickr.com/photos/steviobee/4026463000

you can pull the relay out completly if you want, this will disable the level sense circuit but the coolant temp should still work as normal

Could that level sensor circuit be added to mine? Just out of interest

Is it wired in the fusebox already or would it have to be altered? Sounds like a useful thing to have.

The relay is completely out and the gauge still reads max with the red LED flashing? If i disconnect the sensor the gauge goes to cold - maybe i have the wrong or faulty temp sender, just got it from Euro Car Parts??

the wiring isnt at the fusebox end for it, so you need to add the relay holder and all the wiring.  it could well be a duff sensor, is it a small single pin one with a black collar?

yes John it is the small one with single round pin and black collar, is there a way to test them?

you can with a multimeter yes, 1 pin on the top and another to the earth lead on battery/block/head/wherever is earth.  Should get resistance readings like so:
At 20?C - approximately 1000 ohms
At 60?C - approximately 250 ohms
At 100?C - approximately 75 ohms

I took my dash fasia off the other day and sorted out a few of the boggles and since then mine does the same.  It flashes everytime I hit a slight bump in the road.  Any ideas lads?

Cheers John, have taken measurements and all seems okay, i think maybe i need the relay to get the gauge working properly, its in the post from ebay……
Lee - thats what mine used to do sometimes, i had a loose wire of about one strand left, so have soldered the cable back onto the connector at the sender unit in the engine bay, i guess you might want to check the relay too (if you got one) and maybe give the connector a wiggle at the back of the gauges, mine needs it sometimes to get the dials working properly.
Cheers,
Steve

It's most likely to be that White plug that goes on the bottom of the clocks, can't imagine it could be owt else!

Right this is getting frustrating now,   new relay arrived this morning and has made bugger all difference, i guess there must be a earth fault but weirdly enough the gauge goes down when i disconnect the wire to the sensor? Surely if there was a short to earth it would always read hot even when wire disconnected??
Any ideas??

Did you have the ignition in the on position? (sorry for stating the obvious)

Could it be in moving the wire you inadvertantly stopping the short? In which case it'll be shorting on the bodywork somewhere.

Seems to be all sorted, the wire was shorting on the fuel injection line braiding!!! Doh!! Good luck with your white plug Lee, cheers guys.