Club 80-90 Forums

Dear Friends,
I've read many posts about this subject, and there seem to be two schools..
1. Replace the sensors..
2. Redo the Headup display's circuitry

Let me explain..
1990 Westie.. BUT with a 1900cc diesel Golf lump (Mark 2 I think - it has D/DT stamped on the casing..)

The red light started blinking, I had no option but to go on, fearing the worst, which never came..
The needle stayed stuck in the middle of the gage, maybe occasionally a shade to the right of centre, but never to the top..
I discovered that my mechanic didn't bother to replace the pipe between the two water tanks at the back..
Have done this, but no change..
Checked the temp after a long while revving - Block still only in the 90's, water pipes in the 80's, rad in the 60's - nothing seems to be over heating.. Think I've done about 1000km since this came up..

Suddenly my Indicators stopped working (the green light is solid on, but very pale..) -Changed the flasher relay - no difference 
My dipped light disappeared for a few days, then suddenly came back..
The instrument lights are VERY iffy, and very dim or off..

I've check there's no air in the system, on a steep slope, hot water pumping out of the Rad..
After running for about 40 mins, the fan kicked in, and went off by itself after a while..
As I said, no signs of overheating..

Where would you start, and why!?
Could my blinking red light just be all about the dash wiring? Maybe it's two problems,. and both need doing?
Is there another sensor in the back to be changed too?

Thanks for the help T25 brains!
Jezzer

 

Ok, first thing is to establish the low coolant sender is working , 
disconnect the plug from it and bridge the two pins on the plug , turn ignition on, it self tests for a few seconds and then will go out if the wiring and module and dash are ok….. 

if this results in the light staying on, check the module 42/ 43 connections are not dirty or corroded and that the holder has a good clean earth 

with the sender still bridged out , re test 

next check engine bay earths , diesels are known to have a earthing issue on the sender loom 

also check the 14 pin dash plug is seated correctly and clean 


as for the other issues , they all could be results of dirty or corroded earths and connections 

My red light flashes still if I charge my phone from the lighter socket, even though I've cleaned the earths a dozen times.

sounds like the earth crowns need cleaning and a general check of the wiring under the dash as it is exhibiting myriad symptoms of electrical gremlins
only then can you do reliable diagnostics on the engine to dash signals

Mocki wrote: ↑09 Aug 2024, 21:12 Ok, first thing is to establish the low coolant sender is working , 
disconnect the plug from it and bridge the two pins on the plug , turn ignition on, it self tests for a few seconds and then will go out if the wiring and module and dash are ok….. 

if this results in the light staying on, check the module 42/ 43 connections are not dirty or corroded and that the holder has a good clean earth 

with the sender still bridged out , re test 

next check engine bay earths , diesels are known to have a earthing issue on the sender loom 

also check the 14 pin dash plug is seated correctly and clean 


as for the other issues , they all could be results of dirty or corroded earths and connections 

Fantastic to have a starting point!
Thanks so much, will do and report back..
My issue is that the guy I bought it from was an "electrician" (Or so he claimed..)
"The Fridge was working all the time I had it" - my first night camping in France, I blew the main fuses for the area I was camping in, putting out the lights for about a dozen other campers"
I can't plug the van in, as the fuse board he installed in the back immediately trips! 
No fridge, no sockets.. its a nightmare..
I couldn't open the fusebox, because he seems to have installed a headphone socket there, wires mean I can get to the fuses!!
All this custom wiring (six new touch LED lights.. very nice, but it represents a total debugging nightmare..
I'll start with the sender, and see where that goes..
Then have a look at the Earth crowns..
(Not sure what to look for, but I'm sure I'll know if I see it!)
Then I'll have a look at the earthing points in the engine bay..

Thanks so much everybody!
 

Blinking Red Light - Stopped blinking!!
As suggested I shorted the terminals, not light!" Great..
I decided to check the main coolant tank - EMTPY!!
So the top up tank is FULL, and the faithful Red Light was reporting the fact...
Why isn't the coolant moving from the top up tank to the main tank..
I've filled the main tank directly from the Blue cap (Which hissed when I unscrewed it, but NOT when I first took off the connecting pipe between the two, if that's relevant?) and the coolant light stopped blinking..
Does the main tank need a new blue cap? Do I need a new water pump somewhere?

Thanks so much people..
Electrical debugging next..

Any suggestions where to watch a vid about how to test the Earthing etc..?

jezzer

Almost certainly a faulty blue cap.

Its worth knowing that the capacitor in the temp gauge can fail, leading to erratic blinking even when all is well.

Ok, maybe I should have posted this sooner……
 The system is very simple....
 The headertank ( the one in the engine bay ) should always be full to the brim, and the top up tank ( behind the number plate flap) should be full to the max mark when cold. When the engine is up to normal running temp the coolant expands and is pushed into the top up tank, when the engine cools down the coolant is sucked back into the header tank
blue cap on later vans should be obvious enough if you blow through the spout it will “quack”  
  
 The flashing red light in the temp gauge has two functions ....
 1. If the gauge is above 3/4 and it's flashing it means over heating 
 2. If the gauge is below 3/4 and it's flashing , it means low coolant in the header tank. 

I think it would be worth getting a sniff test done on the main header tank to check for combustion products. The fact that the blue dalek cap hissed when you took it off the empty header tank suggests that the coolant system is being pressurised and that this is pushing all the coolant into the overflow tank. Unfortunately that is a classic sign of a leaking head gasket so this is something that you should try to rule out.

Not to start any alarm bells etc,but a hot and warmed up to temp system will always hiss if you undo the blue cap (I dont recommend it! Keep face well away) , since a hot system is under pressure by nature. That's how the cooling system works.

A compromised head seal will chuff much more pressure into the coolant system than it can handle though, cue bursting pipes and lots of steam etc. So that's when it's a bad thing



E D I T oh... Taking the cap off an empty tank and it hissing, I've not seen that..

silverbullet wrote: ↑11 Aug 2024, 07:28 Its worth knowing that the capacitor in the temp gauge can fail, leading to erratic blinking even when all is well.

This.
 

slowcoach wrote: ↑11 Aug 2024, 21:20 Not to start any alarm bells etc,but a hot and warmed up to temp system will always hiss if you undo the blue cap (I dont recommend it! Keep face well away) , since a hot system is under pressure by nature. That's how the cooling system works.

A compromised head seal will chuff much more pressure into the coolant system than it can handle though, cue bursting pipes and lots of steam etc. So that's when it's a bad thing



E D I T oh... Taking the cap off an empty tank and it hissing, I've not seen that..

If the dalek caps working it will just shunt all the coolant into the topup tank an out the top of it too if it was a gasket failure

Thanks,
Manually filled the tank with the Dalek cap, light gone..
All working well.
Will replace the cap. and see what happens next!
Thanks for all the help..