Reggit 0 Posted November 29, 2004 Ever since I got the car ('93 VR6, in December last year), my temperature gauge has read on the low side, never reaching 70 unless stuck in traffic, and then dropping to below 70 again in clear conditions. I've just changed the blue sensor, for a Vagcom error, and thought I might as well do the gauge sensor at the same time. Blue one no problem, error has cleared. I also changed the Yellow one with 4 wires, is this the correct one for gauge? and replacement one was black, is this ok? Now temp shows lower than ever, only just off the bottom stop after a several mile run. Oil temp comes up reasonable and heater also blows warm quite quickly. Does this sound like a possible stuck open thermostat? Have I changed right sender (yellow)? Why does my Bently manual show the third position blanked off for non-airconditioned cars when I've got another sender in there and what does this 3rd sender do? Sorry about the length of this ramble, but I'm confused. Quote Share this post Link to post Share on other sites
Timo. 0 Posted November 29, 2004 Sounds like your temp guage is buggered!! If the heater blows warm quite quickly then I would say your thermostat is working alright. What oil temp does it run at?? Timo. Quote Share this post Link to post Share on other sites
Heardy 0 Posted November 29, 2004 As far as i know the yellow sender opperates the gauge and the coolant run on pump,i changed the yellow sender on mine and bought one from GSF, after i fitted it the gauge was reading around 130 dergee's C !!! so i ended up fitting one from the mainsteeler and now all's well.Have you fitted a genuine sender or not? Quote Share this post Link to post Share on other sites
Reggit 0 Posted November 29, 2004 Sender is genuine, oil runs at mid-high 90's, although I took it on a 10 mile run tonight and it only reached 74 degrees, from cold with ambient air temp at +1degree. Gauge does reach 100(ish) if stuck in traffic, so I wouldn't have thought it would be buggered. Can I ground one fo the sender wires for it to read full scale? If so which one? Quote Share this post Link to post Share on other sites
Heardy 0 Posted November 29, 2004 Sender is genuine, oil runs at mid-high 90's, although I took it on a 10 mile run tonight and it only reached 74 degrees, from cold with ambient air temp at +1degree. Gauge does reach 100(ish) if stuck in traffic, so I wouldn't have thought it would be buggered. Can I ground one fo the sender wires for it to read full scale? If so which one? Sound's like mine really i don't think there's anything wrong with it though .The heater seem's to warm up okay on mine . I think you need to bridge diagonally across the multi plug to make the gauge read full ,if you bridge it one way the coolant run on pump should opperate and the other way should make the gauge read full scale :roll: ,i'm sure someone will come along to confirm this...... Quote Share this post Link to post Share on other sites
Timo. 0 Posted November 29, 2004 Sender is genuine, oil runs at mid-high 90's, although I took it on a 10 mile run tonight and it only reached 74 degrees, from cold with ambient air temp at +1degree. Gauge does reach 100(ish) if stuck in traffic, so I wouldn't have thought it would be buggered. Can I ground one fo the sender wires for it to read full scale? If so which one? Sound's like mine really i don't think there's anything wrong with it though .The heater seem's to warm up okay on mine . I think you need to bridge diagonally across the multi plug to make the gauge read full ,if you bridge it one way the coolant run on pump should opperate and the other way should make the gauge read full scale :roll: ,i'm sure someone will come along to confirm this...... sounds about right to me! Timo. Quote Share this post Link to post Share on other sites
dr_mat 0 Posted November 29, 2004 Has the thermostat ever been replaced? If not, sounds like you ought to have replaced it first, rather than the temp sender... Reason being, if the gauge *ever* reaches 100 degrees C, then it's working ok. The water being slightly warm will be enough to provide warm air to the cabin, you don't need the full 90 degrees. Quote Share this post Link to post Share on other sites
crazymarcel 0 Posted November 29, 2004 I noticed this tonight on mine, usually it takes no time to get up to 90, but after a quick run for a takeaway and home did not go above 80, maybe it was just the cold weather and taken a while to get warm. oil temp was up to 104 though at one point and cabin air was lovely and hot. Have to keep an eye on it i guess probley just me being paronoid probley, just seemed strange seein the temp gauge sittin as low as the petrol one. Quote Share this post Link to post Share on other sites
Reggit 0 Posted November 30, 2004 dr_mat, I've never done thermostat, and after a quick look through the cars history, it looks as though it hasn't been done. Any tips to change it, as it looks a pain to get the housing off. Cheers. Quote Share this post Link to post Share on other sites
dr_mat 0 Posted November 30, 2004 How to tell your 'stat is stuck: CLOSED: the temp gauge rises steadily from cold and doesn't have a "steady state" for a while at 80 degrees, just goes straight to 100 (or higher), but the RAD FANS STAY OFF. OPEN: the temp gauge rises slowly but steadily from cold, again showing no steady state at 80 degrees. Temp will typically stay on the low side during driving, but will obviously climb to 100 and the fans will come on as normal when stationary. How to tell your sender unit/gauge is faulty: You see the normal rise in temp from cold, followed by a steady temperature for a short while (even if it's not 80 degrees). If you sit in traffic stationary the gauge goes up by about 20 degrees and then increases no further. While this happens, the fans start kicking in/out as normal. Reggit I am aware the 'stat is a PITA to change, Stealth did mine when it was in for the timing chains... Perhaps some kind soul has done a write-up..? Quote Share this post Link to post Share on other sites
Timo. 0 Posted November 30, 2004 Its not too bad to change. Bit fidely to get at but not difficult! Never changed it but I've had the thermostat housing off several times when I had a leak! Timo. Quote Share this post Link to post Share on other sites
Reggit 0 Posted December 3, 2004 To attempt to narrow low temp reading fault down, I've extended wiring loom to yellow sensor so it can be heated externally to the car whilst monitoring the temp gauge. Heating the sensor in a pan to boiling point of water, car was reading only 80 degrees max, I'm assuming the gauge is duff. Can someone confirm this or do they usually read this low? Cheers. Quote Share this post Link to post Share on other sites
Timo. 0 Posted December 4, 2004 Ingenius!!! Sounds like its duff to me. Temp sender on my Dad's G60 is exactly the same. Always read 10-15 degrees under. Definitely nothing wrong anywhere else in the system so we just put up with it. T. Quote Share this post Link to post Share on other sites
Hotcorrado 0 Posted December 4, 2004 Have you check if you have air pockets in the coolant, you might be running low on coolant when you drive, check the coolant level. I hope that this is the right answer. Just trying to help since I had the same problem just recently. Peace! :D Quote Share this post Link to post Share on other sites
