rich_e777 Posted May 31, 2015 Report Posted May 31, 2015 Yeah one more cooling fan thread, but I couldn't find the answers by reading through the old ones. A few weeks ago I noticed the Cutlass would get hot while stuck in traffic and I had assumed it was the design of the water pump impeller being inferior, but its actually my fans that are not activating at the right temperature. I have confirmed power at the relay and also purchased a new one just in case. I have jumped the fans off the battery and they also activate when full AC is on I have changed the coolant temperature sensor on the thermostat housing. They still do not come on normally, Is there something I`m missing or forgot to check and can anyone point me in the direction of what to try next? This is on the 1994 Cutlass 3100 Quote
55trucker Posted May 31, 2015 Report Posted May 31, 2015 (edited) Backprobe the CTS sensor with a digital voltmeter to see what the ohms value is that the CTS is allowing when the fans DO engage, you'll need the GM chart to compare what resistance actually is supposed to pass when the ECM commands the fans to come on at the appropriate temp. a handheld infrared temp gun is useful to see what the rad hose temps are at the thermostat. chart example..... http://www.google.com/imgres?imgurl=http://ww2.justanswer.com/uploads/working4ev/2010-08-23_195643_1.gif&imgrefurl=http://www.justanswer.com/car/3wxdb-1990-pontiac-sunbird-2-0-non-turbo-just-recently.html&h=300&w=300&tbnid=59RxgamoIncciM:&zoom=1&docid=cnIW-1eZL-Ud9M&ei=AZNrVYX3G8SjyATEwoOYCw&tbm=isch&client=palemoon&ved=0CCsQMygPMA8 http://www.autozone.com/repairguides/GM-Lumina-Grand-Prix-Cutlass-Supreme-Regal-1988-1996/ELECTRONIC-ENGINE-CONTROLS/Coolant-Temperature-Sensor-CTS/_/P-0900c15280067e10 Edited May 31, 2015 by 55trucker Quote
RobertISaar Posted June 1, 2015 Report Posted June 1, 2015 you have an ALDL cable, right? maybe i'll do some digging tomorrow to see if I've added in the mode 4 command to force the fans on/off for the P66 V6 definition. otherwise, I would be curious to know what the PCM is seeing for coolant temps. stock settings are kinda nuts, something like 226 for fan 1 and 230ish for fan 2, but I'm going off of memory. Quote
rich_e777 Posted June 1, 2015 Author Report Posted June 1, 2015 Backprobe the CTS sensor with a digital voltmeter to see what the ohms value is that the CTS is allowing when the fans DO engage, you'll need the GM chart to compare what resistance actually is supposed to pass when the ECM commands the fans to come on at the appropriate temp. a handheld infrared temp gun is useful to see what the rad hose temps are at the thermostat. chart example..... http://www.google.com/imgres?imgurl=http://ww2.justanswer.com/uploads/working4ev/2010-08-23_195643_1.gif&imgrefurl=http://www.justanswer.com/car/3wxdb-1990-pontiac-sunbird-2-0-non-turbo-just-recently.html&h=300&w=300&tbnid=59RxgamoIncciM:&zoom=1&docid=cnIW-1eZL-Ud9M&ei=AZNrVYX3G8SjyATEwoOYCw&tbm=isch&client=palemoon&ved=0CCsQMygPMA8 http://www.autozone.com/repairguides/GM-Lumina-Grand-Prix-Cutlass-Supreme-Regal-1988-1996/ELECTRONIC-ENGINE-CONTROLS/Coolant-Temperature-Sensor-CTS/_/P-0900c15280067e10 I think I understand but the fans do not come on automatically, just when I turn the AC on. You are saying to use a temp gun and measure the ohms when the coolant gets hot enough to normally kick the fans on? I can use tunerpro to monitor the temp and get those ohm readings. how hot is it getting to? The needle can get as far as halfway across the gauge, it usually site at the second notch under normal conditions. you have an ALDL cable, right? maybe i'll do some digging tomorrow to see if I've added in the mode 4 command to force the fans on/off for the P66 V6 definition. otherwise, I would be curious to know what the PCM is seeing for coolant temps. stock settings are kinda nuts, something like 226 for fan 1 and 230ish for fan 2, but I'm going off of memory. I do have a tunerpro session recorded but that was a few weeks ago, on it the temp got to about 207F and kept climbing at idle. I`ll try to upload it but its about 15 mins long. My temp gauge in the cluster is working I know and it gets its info from the CTS IIRC. From my readings there is also a resistor in the ECM that can go bad and might cause this. My fsm says the first fan is to come on at about 103-106F and then the second is supposed to come on at 113F(I may be wrong I don't have it in front of me ATM), its seems to me the fans work but do not get the signal to come on at the temps. they are suppose to. As a temporary fix I just cut the AC on full blast for a few minutes until im moving again, Im sure my head gaskets love that. Quote
55trucker Posted June 1, 2015 Report Posted June 1, 2015 When the ECM commands the fans to engage with the A/C the CTS is bypassed, my first thought would be that the CTS is faulty seeing as you state that the fans do NOT? engage at all without the A/C, are you certain you replaced the CTS for the ECM and not the cluster gauge? another possibility is that the reference circuit in the ECM is bad, the wiring for that path has an open somewhere in it. Quote
vipmiller803 Posted June 1, 2015 Report Posted June 1, 2015 The needle can get as far as halfway across the gauge, it usually site at the second notch under normal conditions. I do have a tunerpro session recorded but that was a few weeks ago, on it the temp got to about 207F and kept climbing at idle. Sounds like you are simply not being patient enough. Like Robert said, the kick-on temps are pretty extreme stock, so if you are stock then you have not let the temps get that high. 207 is not bad at all just idling for a long time. I would only worry when I get in the 230's. My fsm says the first fan is to come on at about 103-106F and then the second is supposed to come on at 113F(I may be wrong I don't have it in front of me ATM), its seems to me the fans work but do not get the signal to come on at the temps. they are suppose to.As a temporary fix I just cut the AC on full blast for a few minutes until im moving again, Im sure my head gaskets love that. I am guessing your FSM said those numbers but was in Celsius. Those numbers sound consistent with what Robert said. 106C=222F. 113C=235F. More or less consistent I guess. Your claim was that they are not coming on at the right temp... It seems GM's definition of the right temp and yours differ. I would confirm that the fans do eventually kick on, at the "right" temp (by 226F one should be on). If you are not comfortable doing that, or you want a non-tuning, more crude, solution, you can splice in a resistor between the CTS signal wire and ground. You could also just put a manual switch for the relay(s) like I did. I would not recommend the resistor answer because it would mess with how the car runs a little, especially on cold starts. Quote
vipmiller803 Posted June 1, 2015 Report Posted June 1, 2015 (edited) Just got bored at work so I decided to find out just how impractical it would be to add a simple resistor in parallel going to ground. I used the image 55trucker supplied as an example for my data, then extrapolated for higher temps. Probably would be a little more accurate to just get real data, but the theory still stands. Edit: Ahhh it is barely legible. No excel uploads . MS Word to the rescue! Findings attached. CTS Range.doc Edited June 1, 2015 by vipmiller803 Quote
rich_e777 Posted June 2, 2015 Author Report Posted June 2, 2015 When the ECM commands the fans to engage with the A/C the CTS is bypassed, my first thought would be that the CTS is faulty seeing as you state that the fans do NOT? engage at all without the A/C, are you certain you replaced the CTS for the ECM and not the cluster gauge? another possibility is that the reference circuit in the ECM is bad, the wiring for that path has an open somewhere in it. How many CTS are there? IIRC its just the one on the thermostat housing, and correct the fans do NOT come on unless jumped off the battery or with the AC on max. I have replaced the CTS on the thermo housing but no change. Sounds like you are simply not being patient enough. Like Robert said, the kick-on temps are pretty extreme stock, so if you are stock then you have not let the temps get that high. 207 is not bad at all just idling for a long time. I would only worry when I get in the 230's. I am guessing your FSM said those numbers but was in Celsius. Those numbers sound consistent with what Robert said. 106C=222F. 113C=235F. More or less consistent I guess. Your claim was that they are not coming on at the right temp... It seems GM's definition of the right temp and yours differ. I would confirm that the fans do eventually kick on, at the "right" temp (by 226F one should be on). If you are not comfortable doing that, or you want a non-tuning, more crude, solution, you can splice in a resistor between the CTS signal wire and ground. You could also just put a manual switch for the relay(s) like I did. I would not recommend the resistor answer because it would mess with how the car runs a little, especially on cold starts. I will reconfirm everything tomorrow but I know for a fact it overheats, I`ve had my car long enough to know when its not acting right. I do like he idea of a toggle switch that would allow me to turn the fans on and off without using the AC. I did just drive home in rush hour traffic with the AC on and fans going and the needle stayed at its usual spot, turned the AC off and watched the needle start slowly climbing and then dropped when I turned the AC back on. Quote
vipmiller803 Posted June 2, 2015 Report Posted June 2, 2015 How many CTS are there? IIRC its just the one on the thermostat housing, and correct the fans do NOT come on unless jumped off the battery or with the AC on max. I have replaced the CTS on the thermo housing but no change. One for the ECM (two wire) and one for the gauge (one wire). I have one under the throttle body and one closer to the firewall, both on the LIM, but I do not have a 3100. Looking at pics, it seems like the one you changed is the right one. I will reconfirm everything tomorrow but I know for a fact it overheats, I`ve had my car long enough to know when its not acting right. I do like he idea of a toggle switch that would allow me to turn the fans on and off without using the AC. I did just drive home in rush hour traffic with the AC on and fans going and the needle stayed at its usual spot, turned the AC off and watched the needle start slowly climbing and then dropped when I turned the AC back on. How far up does it climb? You have tunerpro already ready to go so it might be worth checking your "usual" spot and the corresponding ECM temp reading. 55trucker was mentioning the sensor wiring. Tunerpro should reveal any issues there. A high resistance kink in that wiring may be enough to not engage the fans and still not throw any codes. The toggle switch idea for me was mostly because I put a trans cooler in front of that fan, but it works well for the engine too. I wired it with just a diode without separating the ECM from it, but if I were to do it again, I would definitely wire in a relay to keep the ECM's ability to control that fan. Quote
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