WhiteOut Posted February 19, 2005 Report Share Posted February 19, 2005 Okay, so I was reading another post and I came across this: what where you mesuring with, ur stock gauge, thats not accurate I don't understand where this myth comes from. Why is it that no one thinks the stock temperature readouts are accurate? They're based off a thermistor placed in the coolant stream which means the temperature is based directly off the amount of electrical resistance due to temperature fluctuations. Now those fluctuations in resistance are EXTREMELY small so the system has to be sensitive, and even if it uses a mere two significant figures to calculate the resulting temp thats going to give you accuracy to plus or minus 10 degrees which seems pretty accurate to me since we're not exactly talking about a homogenous system. I can see where you could argue that the gauges aren't that accurate since they don't have many demarcations, but I still have to believe that the temperature readout given to the ECM by the computer is a pretty good estimate of the average system temp. Begin the pummeling!!! Quote Link to comment Share on other sites More sharing options...
loominaz34 Posted February 19, 2005 Report Share Posted February 19, 2005 Sounds credible to my uneducated ears. But I've never temp-gunned my coolant when hot because I like my skin. Quote Link to comment Share on other sites More sharing options...
99RegalGS Posted February 19, 2005 Report Share Posted February 19, 2005 Like you said the ECT sensors are preety sensivitve. I pretty sure the temp the ECM sees is within a couple degrees. When I turn to the temp function on the DIS in my Cutlass it goes by single degrees, and The running temp is right above the thermostat opening. Now The gauge in your car probably has a different temp sensor (usually a one wire sensor vs the ECM's 2 wire sensor). I can see that a small problem in the wiring would mess up the gauge quite a bit. Overall I think what the ECM sees is pretty accurate, but I wouldn't trust the gauge as much. Quote Link to comment Share on other sites More sharing options...
1990lumina Posted February 19, 2005 Report Share Posted February 19, 2005 Yeah the system sounds like it is accurate, but I have to say the temp guage itself isn't to accurate. My guage only says 40C at the left left and 125C at the very right and I hate estimating. I'd like if they (GM) had put a few more numbers on the guage in the center and maybe at the quarters also..but that's just me. - Jeff L. Quote Link to comment Share on other sites More sharing options...
WhiteOut Posted February 19, 2005 Author Report Share Posted February 19, 2005 Now The gauge in your car probably has a different temp sensor (usually a one wire sensor vs the ECM's 2 wire sensor). I can see that a small problem in the wiring would mess up the gauge quite a bit. Are you sure? I can't see any reason why there would be two sensors. I mean the cluster gets its information from the ECM anyways so what advantage would having a seperate sensor specifically for the cluster do? And where is this second sensor located at? I think the main problem with cluster readouts is electronic damping not, their inaccuracy. Quote Link to comment Share on other sites More sharing options...
terryk2003 Posted February 19, 2005 Report Share Posted February 19, 2005 i've noticed myself that the temp gauges in the cars are not very accurate...it seems they are off by a percentage or something...because @ a certain temp, like 210* for instance, it'll be right on...but, if it goes over or under that its a few degreees off...i actually thought my car was overheating when i first got it, but i hooked it up to my autoxray scanner, and the fans were coming on @ around 220* like they are supposed to...when the fans come on my guage was on the last mark before the HOT...i've also worked on a mid 90's GP @ work that someone thought was overheating, and i found the same thing, the gauge in the car was just inacurate...the computer temp was a few degrees different from what it reads in teh car... Quote Link to comment Share on other sites More sharing options...
Sherman The Buick Posted February 20, 2005 Report Share Posted February 20, 2005 That's interesting. My gauge goes all over the place..did the same in my 89 and nothing was wrong. Thanks GM! Quote Link to comment Share on other sites More sharing options...
Robby1870 Posted February 20, 2005 Report Share Posted February 20, 2005 My gauge is pretty accurate, I think. Always at ~ 190-195, I can see when the T-stat opens. Ive never had a problem with GP temp gauge not reading correctly unless the sender was messed up Quote Link to comment Share on other sites More sharing options...
pitzel Posted February 20, 2005 Report Share Posted February 20, 2005 I have a DIS. When I start the car at in -20C weather, the DIS reads a -18C coolant temp and it warms up degree by degree all the way to 90-95deg/195-208degF (the hysteresis range of my thermostat). The underlying instrumentation I believe is very accurate which allows for effective operation of the ECU insofar as the fuel maps are concerned. The cluster gauges leave quite a bit to be desired though which is why I am so glad I hooked myself up with a DIS. Quote Link to comment Share on other sites More sharing options...
mfewtrail Posted February 20, 2005 Report Share Posted February 20, 2005 Going by the ECT and comparing to actual temperature readings on an infrared pyrometer(aimed right at/near the ECT), they're close, if not dead on in most cases(from what I've personally witnessed). Quote Link to comment Share on other sites More sharing options...
99RegalGS Posted February 20, 2005 Report Share Posted February 20, 2005 Are you sure? I can't see any reason why there would be two sensors. I mean the cluster gets its information from the ECM anyways so what advantage would having a seperate sensor specifically for the cluster do? And where is this second sensor located at? I think the main problem with cluster readouts is electronic damping not, their inaccuracy. Yes, I'm sure. The LQ1 has the gauge coolant sensor in one of the heads. and the ECM ECT sensor is in the intake manifold. The 3800 in my Regal is the same way. The ECM coolant temp sensor it right under the TB and the gauge sensor is on the intake manifold. Now the DIS in my cutlass displays the ECM's ECT information becuase it pulls this right from the ALDL serial data. Quote Link to comment Share on other sites More sharing options...
WhiteOut Posted February 20, 2005 Author Report Share Posted February 20, 2005 The LQ1 has the gauge coolant sensor in one of the heads What year LQ1 do you have, because I don't ever recall seeing said sensor on my engine!?! Quote Link to comment Share on other sites More sharing options...
mfewtrail Posted February 20, 2005 Report Share Posted February 20, 2005 The LQ1 has the gauge coolant sensor in one of the heads What year LQ1 do you have, because I don't ever recall seeing said sensor on my engine!?! My 1994 engine has the sensor in the head(I believe it's located on the front head a few inches away from the oil cap). Quote Link to comment Share on other sites More sharing options...
Brian P Posted February 20, 2005 Report Share Posted February 20, 2005 Not all sensors give the right readout for the gage. I've messed around with three different sensors (I'm now using the 3-prong single sensor that OBD2 GM uses) all 3 won't give the same reading to the gage when the engine is at 195*. Right now I have a borg warner unit in, and it shows about 180 when I'm at 200. Other sensors would do the opposite, particularly the original "separate" sensor that goes into the head. When I was at 200* the gage would read about 220. However the ECM reading is always pretty good. Quote Link to comment Share on other sites More sharing options...
Prospeeder Posted February 20, 2005 Report Share Posted February 20, 2005 what where you mesuring with, ur stock gauge, thats not accurate i know who MR.X is....LOL and really, none of ur gauges are 100% accurate, ur speedo, tach, all that is inacurate by some degree Quote Link to comment Share on other sites More sharing options...
TeeJay3800 Posted February 20, 2005 Report Share Posted February 20, 2005 When I turn to the temp function on the DIS in my Cutlass it goes by single degrees, and The running temp is right above the thermostat opening. Same here. I have a 180º t-stat and my DIS shows 179-180 degrees consistently while I'm driving. Quote Link to comment Share on other sites More sharing options...
94CutlassSLCoupe Posted February 20, 2005 Report Share Posted February 20, 2005 I know on my CS the Temp in the Guage Cluster reads about 215 or so degrees all the time...while the DIS is reading about 203. Quote Link to comment Share on other sites More sharing options...
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