Guest sam1990rhodes Posted May 15, 2014 Morning, Ive recently had my 20vt off the road for a while due to some much needed repairs, finally started her up again last night to find that the coolant light on the dash flashes permanently, i have checked the coolant levels and they are fine, checked engine temp with a thermometer and it is all fine. a side note, i also replaced the original coolant reservoir (as it was looking dirty/old) with a non OEM reservoir during its time off the road, i suspected that this may be the issue however i bunged up the hole on the old reservoir, filled it with water to between max and min, and plugged it in, the light still flashes!!. does anyone know if anything else causes the coolant light to flash? or does anyone know a way that i can defeat this sensor (i.e. resistor into the end of the connector) to check it is the sensor? as always, all help appreciated :) sam. Quote Share this post Link to post Share on other sites
Sean_Jaymo 0 Posted May 15, 2014 (edited) The coolant light is only a level light, it's nothing to do with temperature. The circuit is straight forward, the 2 pins that go into the coolant reservoir itself sit in a plastic bowl to reduce the effects of surge on the 2 pins. If the level is correct, this bowl is full and the coolant will allow an electrical current to flow between the 2 pins. One pin will get power to it from the fusebox, the other pin will return straight to the coolant bulb in the instruments via the fuse box and if the instruments don't see a current return, it will flash the small LED. There isn't anything else in that particular system. My guess is 1 of 2 things. 1, There is an electrical problem but there are only 2 wires so should be easy or 2, the pins inside the coolant reservoir are corroded over and wont allow a flow of current between them. Either way, buy a new GENUINE bottle man! They are not expensive and the MK4 can be made to fit as long as you have the electrical plug for it. If you want to defeat it and I would definitely recommend that you don't, then just bridging the 2 pins on the cap will cure it. If it doesn't cure it, you have an electrical problem. That light is important, if it flashes, turn of the engine! Hope that helps. Edited May 15, 2014 by Sean_Jaymo Quote Share this post Link to post Share on other sites
Supercharged 2 Posted May 15, 2014 Yeah it will be the bottle - aftermarket ones are pretty awful and can leak too New Corrado ones are very cheap from VW! Quote Share this post Link to post Share on other sites
Guest sam1990rhodes Posted May 15, 2014 cheers guys. in my defence i thought the bottle i was buying was genuine, turned up and wasnt, thought id give it a go.. never again!. so if I was to just unplug the connector and run a piece of wire between the 2 terminals on the connector it should stop the light from flashing, if it doesn't stop it the fault is elsewhere? if the above does prove the bottle is naff ill pop and get a genuine VW reservoir tomorrow. Quote Share this post Link to post Share on other sites
Guest sam1990rhodes Posted May 15, 2014 http://www.ebay.co.uk/itm/VW-MK2-Golf-GTI-Genuine-OEM-Later-Round-Coolant-Bottle-BRAND-NEW-STOCK-/271412344292?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item3f316fb5e4 argh £65! Quote Share this post Link to post Share on other sites
Sean_Jaymo 0 Posted May 15, 2014 VW Heritage £14.40 and in stock. eBay isn't the cheapest anymore and is full of con men like this! Quote Share this post Link to post Share on other sites
mic_VR 3 Posted May 15, 2014 eBay isn't the cheapest anymore and is full of con men like this! Amen to that! Quote Share this post Link to post Share on other sites
Guest sam1990rhodes Posted May 15, 2014 cheers Sean, to check though, that £14.40 is genuine vw, right? Quote Share this post Link to post Share on other sites
Supercharged 2 Posted May 15, 2014 Just phone VW and buy a Corrado one - last one I bought was £12 + vat Quote Share this post Link to post Share on other sites
Guest sam1990rhodes Posted May 15, 2014 Rang local VW... £54.42 inct VAT! argh! Quote Share this post Link to post Share on other sites
diarmaid16 1 Posted May 15, 2014 http://www.vwspares.co.uk/corrado_cooling.php Expansion tank is down the page a bit. Any use? Quote Share this post Link to post Share on other sites
Supercharged 2 Posted May 15, 2014 Rang local VW... £54.42 inct VAT! argh! Is that this part number - 5X0121407A ?? Quote Share this post Link to post Share on other sites
carrots 1 Posted May 15, 2014 i had a prob with temp light flashing,put a aftermarket tank and a genuine on.sure is was something to do with a connection on a relay or fuse in the end Quote Share this post Link to post Share on other sites
VW_OwneR_85 2 Posted May 15, 2014 got this problem with my audi a4 1.8t , weirdly enough the light doesn't flash with the sensor unplugged so its staying that way. Quote Share this post Link to post Share on other sites
Guest sam1990rhodes Posted May 18, 2014 hiya, an update, tried cleaning and attaching old resevoir, still flashes... i got a little miffed with this so cut the connector off and spliced the two wires together and it still flashes!! (reconnected connector now). anymore ideas? as this is a 1.8t loom spliced in to a rado loom is there anything else that could be setting this off? Quote Share this post Link to post Share on other sites
Sean_Jaymo 0 Posted May 18, 2014 Has the light ever operated properly? Quote Share this post Link to post Share on other sites
Supercharged 2 Posted May 18, 2014 It will also flash if it thinks the car is overheating - look at the other water sensors! Quote Share this post Link to post Share on other sites
Guest sam1990rhodes Posted May 19, 2014 It worked correctly before. coolant temp sensor on the engine block works i assume as it picks up the temp of the engine in vag com, the only other thing i can think is that i replaced the rad, rad temp sensor and fan.... fan was replaced with a slim line after market 12v fan that involved me splicing the two wires from the rad sensor in to one to turn the fan on and off, although the problem with the flashing light starts straight away, the fan only kicks in at around 70-90 degrees? Quote Share this post Link to post Share on other sites
Sean_Jaymo 0 Posted May 19, 2014 The light is only a level sensor. It has nothing to do with anything else. The fans come on at 96 or so normally. You can change the sensor in the radiator so that it comes on at 70 or so. Quote Share this post Link to post Share on other sites
Guest sam1990rhodes Posted May 19, 2014 so the fan is engaging correctly which is good, the temp sensor on the engine block displays on the dash temp level gauge as slightly lower as the sensor is the black and yellow one due to the old sensor not reading at all on the dash gauge (http://www.autohausaz.com/secure/PartImages/357919501A.jpg)but Vag-Com reads the correct temperature. The coolant level is fine, smack bang between min and max. What else could be causing this if everything is reading fine! note: I have counted it and it takes the coolant level light to come on exactly 18 secs after the engine starts no matter if its cold start or off then back on after running. The loom is half AGU and half corrado, Could the chap that made the loom have wired anything to make the light flash for anything else? (Andy Outhwaite and ACR made the loom) Quote Share this post Link to post Share on other sites
Dox 23 Posted May 20, 2014 What voltage reading do you get at the plug? Quote Share this post Link to post Share on other sites
Guest sam1990rhodes Posted May 21, 2014 ill check later and let you know. Quote Share this post Link to post Share on other sites
davidwort 0 Posted May 21, 2014 It may be the temp module in the dash itself, is it an original Corrado gauge? Quote Share this post Link to post Share on other sites
Guest sam1990rhodes Posted May 21, 2014 the gauge is original, it worked before i worked on he engine bay so i suspect its something ive inadvertently done. Quote Share this post Link to post Share on other sites
