Coolant light flashing

[MattRocco]

Hi guys,

Every now and again the red light flashes on the temp gauge when I'm driving. Now I know it has a level sensor too so I don't know whether the light for level is in the gauge or with the cluster of bulbs underneath and the cars over heating?!
I can't see any leaks but usually pull over and top the fluid up and the light seems to go off but I thought the gauge one would be for overheating not level? I have no idea.
Also if it is overheating anything common?

Any ideas much appreciated.
It's a 1.8 kjet gtx on 155k (if that makes any difference)


Regards
Matt

[mark1gls]

There is no flashing light for over heating just the big gauge and worry when it gets to the red, the light is for low coolant level you could have a pretty empty expansion tank and the car would still not over heat as there is more than enough coolant in there.
The light usually flashes if you are losing coolant and have to keep topping it up you have a leak and need to find it or the sensor in the expansion bottle is rusting away as it has 2 metal prongs which live in the coolant. It could also be electrical as coolant can creep up the wires (like a wick) and rust away the wires or finally it could a dirty connectors on the relay or faulty relay (I can't remember the relay number but it lives on top of the fuse box)

edit found some more info... relay no 42
http://vwgolfmk1.org.uk/forum/index.php ... st_1246458

http://vwgolfmk1.org.uk/forum/index.php ... st_1301124

[MattRocco]

Thank you for the information! I'm glad it's not a over heating light. I know the fans kicking in as when I park up after getting home from work I can hear it going so I was thinking it was more to do with level.

I will give it all a check over at the weekend and check the wires etc.

Again thank you for the help!

Regards
Matt

[mark1gls]

Mines been flashing on and off for about 3 years in my Mk1 golf, after fitting a new sensor and cleaning the connections to the relay it's not fixed mine. Not got around to looking at the wiring etc yet as other things needs attention before the flashing light.
I've just stopped looking at it now....

As long as you keep an eye on the coolant level in the expansion tank and temperature gauge you'll be fine, the Mk1 scirocco and some Mk2's never had the flashing light fitted.

[whiteshark]

You may have a very slow leak. Like Mark said you would really need a major leak for your car to overheat, hence the expansion tank. If you loose a small amount of water it does not look like much in the expansion tank but the light will start flashing. A quick top up and it should last you for a week or two before the next small top up of coolant or water.

[MattRocco]

Hi guys, the light came on flashing as I came to work today, luckily I was close to work. On my guage at normal driving when the car is at temp the needle site almost dead centre but fractionally to the right.

When the light came on today the needle seems to be a lot higher then where it usually sits on normal driving.

Also as I got to work and parked up I couldn't hear the fan coming on which usually after that drive it does. I'm thinking I have a over heating issue caused by the fan not always coming on, maybe a electrical issue?



Any help appreciated

[mark1gls]

Yes that is a little high, was the fan running when the temperature was that high?
The fan normally kicks in when the gauge gets to 3/4 and then brings it back to 1/2.
Is there plenty of coolant in the expansion tank, above the min mark?
Have you done anything to the car just before this started to happen?

[MattRocco]

No not done anything to it just started to do it last Friday then fine over weekend and did it again yesterday and today, I can't hear if the fans on unfortunately due to a loud exhaust (previous owner not me) but I'm sure it isn't. Strange how it doesn't do it everyday on the same drive. Just had a quick check level is a fraction under max, slight white residue around cap and also on rad switch.

Just been gsf and got a coolant temp sensor, rad switch, thermostat, coolant level sensor and cap and fresh coolant all for £35 so will do all that at weekend along with checking wiring and clean any bad connections etc.

Hopefully will be sorted!

[mark1gls]

Very strange how it just starting doing this but changing the thermostat (as they do sometimes start to stick open or shut) and fresh coolant etc is a good start.
My fan does not come on very often unless sitting in traffic for a while and temperature gauge at 3/4, your fan must be working if you can hear it when leaving the car.

[MattRocco]

Yeah it's not every time, but most days/night when I get to work and home I hear the fan going as I leave the car but when the light is on it doesn't seem too. Will see how I get on this weekend, fingers crossed!
Appreciate all the help

[MattRocco]

Figured it out finally and realise I should have done this from the start but oh well some things slip the mind!!

Driving home from work today and as expected the light comes on, pull into a lay by and switch her off. Popped bonnet and the levels all good. Don't know why I haven't before but checked the hoses, top one is boiling hot and bottom one is cold as. Gave the pipes a few good squeezes to see if I could get some fluid flowing past the stat to maybe force it open atleast a little.

Waited about 15 mins so she could cool down. Drove home, and as I parked up the fan kicked in! I'm assuming the stat is sticking more often then not so will be all sorted at the weekend hopefully :)

[ThomasD]

Glad you got it sorted out!

In case anyone looks at this thread in the future, I just wanted to add what I know about about the coolant level sensing system from going through it on my Storm...

The way the coolant level controller works (its not a relay) is that if it detects the coolant level is low, it actually simulates an overheating condition as far as the gauge goes. With the earlier version of this controller, if the coolant level was low, the controller would signal the gauge would move to the hot position and the LED would flash. The bad thing about this is it is impossible to tell the difference between slightly low coolant and an overheating car by looking at the gauge.

The newer version of the control unit works differently - it pulses the signal to the instrument cluster such that the LED flashes, but the needle does not move to the hot position. With this control unit you have a better idea when the LED flashes if it is because the coolant is low or the car really is overheating.

Here are some reasons the LED will flash:

1. You just started the car - the LED should flash for a few seconds and shut off - this is normal.
2. Car is overheating (needle will move up as well). All the usual reasons - thermostat, water pump, electric fan not working, etc.
3. Coolant Level is low. Needle may or may not move towards full hot position - depends on controller version.
4. Capacitor in gauge itself has gone bad. In this case the LED might flash all the time including when the car is ice cold (had this happen)
5. Coolant Level Control unit has gone bad (had this happen too).
6. Coolant level probe in expansion tank is bad
7. Wiring problem (i.e. bad connections on coolant probe, bad earth connection, etc).

Tom