Context - Audi TT R32 engine, MK2 Golf, CE2. Question - does the temp gauge on the dash measure oil temperature or water temperature? Which sensor on the engine feeds the gauge? Reason for asking - temp gauge doesn’t really go above quarter mark since the engine swap. It used to go to about 1/2 in normal driving. The fans switch on at about 1/4. Yesterday, sitting in traffic the coolant reservoir overflowed but gauge still showed 1/4 or thereabouts.
This ^^ Did you swap the sensors on the engines or just plugged fitting connectors to sensors? I can imagine there is a different sensor connected and therefore the read-out is also different?
OK, I went and checked on the car because I couldn't remember if there were 3 or 2 temp sensors on the head, but is is 3. There are 2 on the left side, and one on the rear side, also on the left of it. One of the sensors on the side has a Bosch-Junior style 2 pin connector. It's for watertemp to the ECU. The others are connected with spades; the one on the side (yellow/red wire) is for the coolant temperature as well according to A2resource (D29 to B07). The one on the rear of the head is then the oil sender for the MFA, it also has a mass wire which is bolted with the valve cover bolt.
OMG! I’ve just realised I’ve been thinking about the oil temp sensors in the oil cooler. The coolant temp sensors are in the thermostat housing!! Of course they are . So not mk2 at all, they are the same as the mk3. So, my question now is, is the sensor connected directly to the gauge or is it connected to the ECU which then supplies the signal to the gauge??
MK1/2/3/4 all have a separate sensor for dash, what you have depends on the loom builder. MK1/2 have a separate 1 or 2 pin sensor for dash, mk3 8v have a 4 pin sensor which does dash and ecu and the VR6 uses a blue 2 pin temp sensor for ecu and a yellow 4 pin for dash and fan control module. MK4 also has a single 4 pin sensor which does the ecu and dash, but the dash sensor isnt compatible with MK1/2/3 cluster. MK5 just has a single 2 pin for ecu which feeds dash over can-bus when doing a swap many swap the MK4/5 sensor for a 4 pin MK3 8v dash/ecu sensor. Or you could replicate VR6 setup, or leave the original ECU sensor alone and add a black 2 pin just for dash. Some leave the mk4 sensor and add a resistor which corrects the resistance curve for use with mk1/2/3 dash
Thanks John, lots of info there, very helpful. Will have to see what we have. I think just one sensor. If I want to add a black 2 pin sensor just for the dash where do the wires run to?
If your dash temp worked fine before then what I would do is replace the sensor you have, easier than messing with the wiring. If you wanted to use the 2 pin instead then you would cut the 2 dash temp wires off whatever sensor you have now and wire them to it, which wires and where depends what sensor you have now
All of the ECU sensors I mention are the same curve so no worries on that side of things. In a nutshell, take a.picture of what you have now and we can go from there
Ok so the original MK4. Do you know if the loom guy put a resistor in for dash temp? If so you can just try another one. Basically your options when converting a MK4 engine: add resistor inline with dash temp wire, keep MK4 sensor Keep MK4 sensor, add MK2 or MK3 dash temp sensor and wire dash to that. Ignore mk4 temp sensor wires Chop MK4 plug off & splice mk3 4 pin plug, use mk3 4 pin sensor (no resistor needed) With a mk5 which just has a 2 pin for ecu, you need to add another sensor regardless. any MK2/3 will do you fine and you should have 1 or 2 spare slots in the coolant flange for it. If not swap it for a mk4 one
@rubjonny or anyone else. Likely to do this tomorrow. We are going to splice in a MK3 plug and use a MK3 sensor. Does it matter which wires goes to which pin on the sensor/plug?
Sure does, pinout in here: https://www.clubgti.com/forums/inde...install-faq-now-with-added-dieselness.267196/
Right, straightforward it never is. This is what I have. 2004 Audi TT R32. I can clearly see 2 and 4 marked which appear to be 2-brown and white and 4-black. In the below (lifted from your link above) that would match with 3 and assuming black is earth that would make sense for 4 instead of the brown/blue shown? I am left with purple which seems to correspond to 1 if that is the pin opposite 2. And green which, by process of elimination, is pin 3. So! The wires I have…… Purple to pin 4 on mk3 Green to pin 3 on mk3 Brown/white to pin 2 on mk3 Black to pin 1 on mk3 ******************************************* MK3 sensor pins: 1 - brown/blue - ECU sensor earth 2 - brown - dash sensor earth 3 - blue - ECU sensor signal 4 - yellow/red or blue/white - dash sensor feed Late MK4 sensor pins: 1 - purple - dash sensor signal -> MK3 plug pin 4 2 - brown/white - dash sensor earth -> MK3 plug pin 2 3 - grey/yellow or blue - ECU sensor signal -> MK3 plug pin 3 4 - brown/blue - ECU sensor earth -> MK3 plug pin 1
