temperature needle moved to right, LED permanently flashing

[Tropical Pete]

1984 watercooled T25
The needle on the temperature gauge has all of a sudden decided to shift totally over to the right and the LED is permanently flashing. The engine has been off now for around 2 hours but it's still doing it as soon as I start it up.

[nesty]

Probably as your coolant in the header is low. On the early models when header tank gets low, red light flashes & needles swings to max right.

I changed my relay to the modern version, where red light will flash (if header low), but won't swing the needle.

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[Stesaw]

Check the connector on your header tank make sure it isn't loose, possibly (unlikey) might need a new sensor.
Have you checked to make sure you have enough coolant in the system as well?

[nesty]

The header tank (one in engine bay) must be full to the brim, it doesn't take a lot for level to drop & set off the sensor. So check the levels first.
My levels were dropping due to faulty darlek cap, tho replaced that & upgraded the relay & all good.

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[Tropical Pete]

when you refer to coolant in the header and have you checked you've got enough cooler etc. do you mean in the water/coolant bottle behind the number plate? there's plenty there.

[jrt]

Top up tank behind the flap in between min/max. Pressurised tank left hand side of engine bay should be full to the brim. I had the same problem on my '83 DG and it was a loose connection on the sensor.
David.

[Tropical Pete]

not checked the 'expansion tank' yet if it's not full to the brim can i top it up with plain water for now?

[937carrera]

Yep,there's about 16 litres of coolant in the system

[Mocki]

not checked the 'expansion tank' yet if it's not full to the brim can i top it up with plain water for now?

Yes.water is fine , the system hold 17l so a litre of just water will make no odds

Red flashing coolant light


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.

If it's say low coolant , and you can see the header tank is full to the brim ( not the number plate flap top up tank) then it's an electrical issue , and simple fault diagnostics will need to be employed !

Red flashing coolant light self tests when you switch the ignition on and then goes off ......

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
If it's a late system you join the two connections of the temp sender plug together
This should result in the gauge going to the hot end and the light flashing

[Tropical Pete]

Thanks chaps, most helpful. I wish there were a way of clicking a 'like' button on here etc. I'm a complete quim when it comes to engine jiggery pokery but I suspect that with your help and persistance I'm going to get the hang of things.

[Stesaw]

The system is very simple....

I was told by one of my local garages that the coolant system is very complex. I had them swap out the coolant pipe between the pump and thermostat as the old was had cracked and was leaking.

I mean it was so complex they didn't even fill or bleed the system, I only found that out when I was down in Devon the next day overheating due to low coolant a good start to that holiday hah.

[Mocki]

The system is very simple....

I was told by one of my local garages that the coolant system is very complex. I had them swap out the coolant pipe between the pump and thermostat as the old was had cracked and was leaking.

I mean it was so complex they didn't even fill or bleed the system, I only found that out when I was down in Devon the next day overheating due to low coolant a good start to that holiday hah.

Yes, you won’t be the first or the last to fall foul of numpty garages ....

I have a rule, no one works on or supplies parts for my van who is younger than my van
Right pissed the europants school kid off when I told him that after he had failed to find the right part three times in succession.

[Stesaw]

The system is very simple....

I was told by one of my local garages that the coolant system is very complex. I had them swap out the coolant pipe between the pump and thermostat as the old was had cracked and was leaking.

I mean it was so complex they didn't even fill or bleed the system, I only found that out when I was down in Devon the next day overheating due to low coolant a good start to that holiday hah.

Yes, you won’t be the first or the last to fall foul of numpty garages ....

I have a rule, no one works on or supplies parts for my van who is younger than my van
Right pissed the europants school kid off when I told him that after he had failed to find the right part three times in succession.

Ha, I had to find the correct pipe myself! The part they found was out of stock and they couldn't get for two weeks.. when I asked for the part number they had for it and looked myself it was the wrong one! Apparently they only deal with VW Heritage for parts..seems odd as I can think of at least 3 others suppliers, but OK. I got the right pipe ordered and delivered to me within 24 hours, easy enough right? or am I meant to make it as difficult as possible?

I'm glad I don't have that rule, otherwise I'd be in a pickle as I'm a year younger than my van!

[Mocki]

its common for folk that frequent this place to buy and supply the parts they want fitting to their vans if they cant do the job themselves, its safer, and often much cheaper !!
anyhow if you are younger than your van, you ought to be the one laying under it !!

[Stesaw]

its common for folk that frequent this place to buy and supply the parts they want fitting to their vans if they cant do the job themselves, its safer, and often much cheaper !!
anyhow if you are younger than your van, you ought to be the one laying under it !!

I've spent more time lying under it than in It! haha

but it's all good I'm enjoying it so far