Engine Temp sender

Hey

The Engine temp on the instrument cluster no longer moves, although when i start the car the light comes on flashing for few seconds.

I have gone previous threads, and i understand that it could be the panel behind the cluster that needs a good cleaning, and i have seen Brians post about repairing the actual guage. However, i feel it is the sensor in the engine. Before i conclude this i understand i can earth the plug and start the gauge to see if it goes to full…..this is a basic question but how do i earth it? Connect a wire to the earth and put it to the body of the car?

Secondly, does anyone know what the part number is for thr sender? Its a two pin (ive attached a picture)

If it is the sender how do i replace? Wasnt too sure via the threads- does it just screw off? Thanks

Take a 9V DC battery.
Make a extension for the + and - side of the battery.
Remove the Sender connector.
Connect the -9v lead to the brown wire.
Connect the +9v lead to the yellow red.

Go in to your car and see if the temp gauge goes between the 3/4 mark and the full hot.  If it does, then leave it on for about 2 minutes.  If the Gauge goes and stays there for 3 minutes, you have just tested the Gauge and the wires to it.  

This leave your sender as the issue.

If your fuel gauge doesn't work as well then the issue is your 10V stabilizer on the back of the cluster.

If your Water gauge is the only thing effected, then if the gauge registers, your issue is the sender, if it doesn't then it's the gauge.

Oh, and you don't need the ignition on to test the gauge with the 9v battery.

I unplugged and pluged the wires onnthe sender, twisted the sender abit and i seem to have some movement on the temp gauge lol. Normally when id start the car it would go halfway instantly…..was that correct?

Briano1234 i came across your comprehensive guide in one of the threads….i will get hold of a 9v batt to rule out other things.

The engine temp sender is located below the flange…i have noticed on theother threads some engines have theirs located on the top?

Senders come in many sizes and locations over the years.

The Cabriolets moved from the Side flange to the Front flange (single pin), and then with the 90's they went to plastic fargin flanges and 2 lead senders.

The Diesels went from a side mounted sender to a front mounted sender.  They also on a single pin can either be white or black.

The Cabriolets have a black or white, I have seen blue single pin that is either on top of the flange or under it, I suspect it all depends on where it was installed.

The 90's cabbies have 2 senders named the same thing Coolant Temp Sender, and each is different.  The Blue one is for engine management (Digifant controller) whereas the Black one is for the water temp gauge, and I have seen folks get the connectors on wrong.

The black/green wire is for the CTS (blue) sender on the 90ish digi,  where the yellow/red brown is for the coolant temp sender to the gauge…

Now then all gauges must have good grounds, so you need to clean your grounds or replace them from Battery to Frame and Frame to engine.  The digifant controller is screwed to a metal frame that is Screwed in to nylon fasteners and clipped at the back with a Nylon covered slot.  So you have to be sure that your controllers ground strap is good to the frame.

Conversely you need to insure that you have a good frame ground to your cluster, as the single pin senders, and such need a good ground point to reference the changing resistance of the sender.  The Digi-ish needs a good ground on the Frame as well as they are in plastic, and grounded to another point.

The Clusters #2pin (brown wire) really needs to have an additional ground spliced in to maintain relativity to the frame for aging connectors and wires so that is why I mentioned it in the how to improve cluster grounds and connections how-to in the link on my signature.

Installing a single piece of electrical tape under the mylar tongue of the mylar connector on the instrument cluster (clocks) insures that you have better connectivity to the pins that have probably lost tension from 25-over 30 years of use.

Yep I am death on proper grounding.  Military drummed it in to me.  Computer repair since late 70's Hammered it in even more.  Not that I didn't learn Grounds from Lucas wired cars in my youth…  

Fixed many a things over the years because of Ground Faults…..

Twisting the sender isn't really doing anything, but twisting the wires on the sender to "clean" them.  From your picture they look soldered.

Now I am a Big fan of Solder and Heat Shrink, but I too know from years of use that Solder joints and weaken and get "Cold Soldered".

One of the biggies that I have seen on the Cabriolets is that the Water Temp Gauge is a Electric heater, and there is alot of heat on the stud from Current flow and iffy grounds so much so that the Stud becomes Cold Soldered to the nicachrome wire that the gauge uses.

So cleaning the nicachrome wire with a knife Removing the old solder and renewing it usually repairs the gauge to years of proper workage.

The 89 and under CIS systems use a fuel pump relay that is prone to these cold solder joints so you are running down the road and the car dies, you try to restart and no fuel pump.  The Pins on the relay over heated melted the solder and you loose connection to the relay and Fuel pumps die… Wait 20 minutes or 10, and the solder cools and makes a "cold" soldered connection and you can run down the road again for a while till it repeats….  

Once a connection is cold soldered, you can't reuse the solder, you have to Suck it all out, then clean the connection areas with Sandy Paper, to remove the corrosion, then re-tin and Solder with fresh rosin core solder.  This "new" connection will last for a few years or more.  I have seen 40 year old solder connections on airplanes that look factory fresh the old 60/40 tin/lead can't be bested by the new stuff….

A cold solder joint if you look at it even after cleaning on a pin will let you see a circle around the item being soldered and usually a Gray non-shiney connection that has a circle around the pin.  

Once you remove the older solder clean things up a bit and flow new solder in to the connection you can see what I am talking about.

Like I said too many years of Bad grounds, and cold solder joints.  

Then there are folks that can't solder for spit, and their soldering looks like a bad welding job, splattered, globby and now free flowing…..where joined wires look Chrome plated and you can see individual strands of chromed wire….  It's an art, and you have to practice it.

I suspect that is why they made Crimp connections for folks who couldn't solder, and mass production of harnesses.

Lol thanks Briano1234 for the very useful information - really appreciate it.  

I can see now why you are passionate about soldiering as the two wires clinging on to its dear life has come off the plug ……now can i reuse the same plug or do i need to buy another one?

Mines defo a two pin black sender…

Damn it

With the correct pin remover you can re-solder the wires.

But I do think that the connector is avail at VWheritage or any generic local Breakers, it is a common connector.

Just cut the new wires off the loom with room to solder.

https://www.vwheritage.com/251919501d-coolant-temperature-sensor-blackgreen-2-pin-20mm-vw-spare

So this is the sender i require.

Unfortunately the 2 pin connector, the wires snapped inside it…..

What specific tool would i need to pull the two pins out of the connector as id like to soldier the wire to these so it remains strong to the cause….something like this for eg https://www.amazon.co.uk/dp/B07D3RCVRW/ref=asc_df_B07D3RCVRW54418832/?tag=googshopuk-21&creative=22146&creativeASIN=B07D3RCVRW&linkCode=df0&hvadid=258366679845&hvpos=1o2&hvnetw=g&hvrand=1239010420331940360&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9045937&hvtargid=pla-453195685896

or:
https://www.automotive-connectors.com/delphi-15327868-pt-full-assembled-037-906-240-2-way-black-2-8-timer-sealed-female-connector-assembly.html?___store=english&gclid=CjwKCAjwkYDbBRB6EiwAR0T_-rnlYzVOibuWk0x1E-h-TN55IqMm1N_qt_1sTWyExnTHmwYaYYxWJBoCcksQAvD_BwE

Thanks for the link Briano1234 …..i managed to repair the two pin clip albiet some cowboy soldiering 🙈🙈🙈

The Temp Gauge seems to be moving again slightly.

I have ordered a new sensor to put in, and hopefully this should solve the issue.

So although things were going fine....i noticed whilst the enging temp sender guage was half way it dropped.....ive never seen that happen?!

That is the sign of a flaky Water temp gauge, and that you need to take it out of the cluster and clean and re-solder the connections.

The Gauge internals are like a toaster.  The Brass studs can get cold solder joints.  The higher the voltage the higher the heat on the studs and the things get cold soldered loose connection and then cool off and re-connect rinse repeat.

Briano1234 hi mate just resurrecting this one as ive done the 9v battery test and my temp guage didnt move but could hear a click from i think behind the driver dash.  Guessing its a relay clicking? Is my 10v capacitor the likely culprit? Btw my odomter doesnt work (speedo does) so need to take it out to remove that anyway. So  could do both jobs at the same time if capacitor needs changing out. Thanks for any advice

there is no 10 V cap it is a 10 volt stabilizer.
If your fuel gauge is working it is fine.

Using a 9 v battery tests all the wires from the sender to the gauge, and you don't need ignition on.. gauge that doesn't move bad gauge.

with a dvom and set on ringer you can test continuity from gauge to the gauge with a length of wire.

4 cabbie i have owned 89,90,92,93…all had flakier than ever.  all were repaired by disassembly and replacing the bad solder with new,

Briano1234 thanks for the quick reply. I’m fairly confident the wire from sensor to the gauge is working as I can here a click when I connect the 9v battery.
I could change the sender but as you say as my fuel gauge is working I suspect it the temp gauge.
So guess it’s best to order one from Heritage or similar?
And the remove the gauges console and replace if you agree?

Ok so just to add to the fun I took it out for my first decent drive since I bought it a couple weeks back. And the temp gauge worked perfectly! Perhaps the connector was a bit grubby so unplugging kg and putting it back on a couple of times fixed it. A mystery. I’ll see if it stays fixed..!

If it doesn't last well you can fix the meter you have.

My 86 cab has developed the same problem… needle on temp gauge not working 
But Red light flashes when ignition turned on
Can you Tell me where the sender is ?

It is on the front of the engine water outlet, should be black single pin.