ftpiercecracker1 Posted March 24, 2013 Share Posted March 24, 2013 I probably just need to replace the sensor, but i just wanted some reasurance. My electric fan is not wanting to turn on. I have let the truck warm up on two separate occasions, letting the needle just pass the last line before the orange/red zone and still no fan activity. I have tested the sensor, the one in the rad, in a pot of boiling water and it would appear to be working. Water starts to get a little bubbly and resistance drops to zero. I have also tested the circuitry, using a jumper wire i have connected the two wires that are in the sensor plug and the fan immediately kicks on and you can hear the relay click. Fan is new for all intents and purposes. T-stat is brand new, just put in a few hrs ago. Proper coolant level and bleeding have both been done. Lower radiator hose is getting very hot, so sensor is getting access to coolant flow. Since everything is working and fan still doesnt turn on my only conclusion is that the sensor is indeed bad, even though it would seem not to be. ftpiercecracker. Link to comment Share on other sites More sharing options...
Keyav8r Posted March 25, 2013 Share Posted March 25, 2013 The sensor may not be bad. Put a thermometer in the pan and see at what temperature the contacts close. I'm sure someone on here knows at what temp the electric fan is supposed to turn on and you check your sensor against that. You can pick up a cooking thermometer at WalMart or most grocery stores. Or, just let the truck get a little hotter and see if it kicks on. I think the standard thermostat is 195F. It's a closed, pressurized system so the coolant won't boil until you get well above 212F and you should be safe letting it get a little hotter. The accuracy of the temp gauge is also an unknown factor. Link to comment Share on other sites More sharing options...
ftpiercecracker1 Posted March 25, 2013 Author Share Posted March 25, 2013 Yes the OEM t-stat is a 195* and I know it and my gauge are working right on the money, because it warms up pretty quick but when it hits 200ish degrees the temp hits a brick wall and takes a good 20min for it to heat up the rest of the way. I know what the guage reads isnt acurrate to what is at the sensor, because the gauge input is coming from the very back of the head which is the very hottest part of the engine, but still i would think if the gauge says 245* then the rad would have to be over 220* If i can just get the stupid fan to work this thing would be good to go. Link to comment Share on other sites More sharing options...
cruiser54 Posted March 25, 2013 Share Posted March 25, 2013 Sensor closes at either 208* or 218*. I forget which one. Link to comment Share on other sites More sharing options...
ftpiercecracker1 Posted March 25, 2013 Author Share Posted March 25, 2013 Sensor closes at either 208* or 218*. I forget which one. Then somthin aint right, cause i know the rad is over either one of those and the fan does not turn on. But what is strange is that the sensor worked in the pot. :hmm: I have the old sensor from the donor vehicle, its located in the T-stat housing. Has anyone adapted the Renix to work off this sensor? Link to comment Share on other sites More sharing options...
jons87mj Posted March 25, 2013 Share Posted March 25, 2013 With the sensor that low the coolant will cool down befor it reaches the senser. If you move it up to the thermostat housing then it will read the hotter coolant and will turn on sooner Link to comment Share on other sites More sharing options...
ftpiercecracker1 Posted March 25, 2013 Author Share Posted March 25, 2013 With the sensor that low the coolant will cool down befor it reaches the senser. If you move it up to the thermostat housing then it will read the hotter coolant and will turn on sooner Ya, but do you have a way to adapt the Renix sensor to that location? If i knew of a way to do that I would have done it a while ago. Link to comment Share on other sites More sharing options...
cruiser54 Posted March 25, 2013 Share Posted March 25, 2013 Renix sensor is too big to put in the t-stat housing. What if the circulation through the radiator wasn't good and hot coolant wasn't getting to the sensor? Link to comment Share on other sites More sharing options...
87manche1 Posted March 25, 2013 Share Posted March 25, 2013 Summit racing sells a sensor for the thermostat housing wire in a relay and good to go. Link to comment Share on other sites More sharing options...
cruiser54 Posted March 25, 2013 Share Posted March 25, 2013 Summit racing sells a sensor for the thermostat housing wire in a relay and good to go. Why not use that sensor and the existing relay? Link to comment Share on other sites More sharing options...
87manche1 Posted March 25, 2013 Share Posted March 25, 2013 Kinda like this http://m.summitracing.com/parts/prf-30102 Link to comment Share on other sites More sharing options...
87manche1 Posted March 25, 2013 Share Posted March 25, 2013 U could but i like the direct approach i don't know conditions of his wiring. I like to take ignition voltage from the fuse box run it threw the coolant sensor to the realy then to ground. For power for fan + to relay then relay to + fan then fan-, to ground. Had this set up on 2 diff jeeps worked great. Link to comment Share on other sites More sharing options...
87manche1 Posted March 25, 2013 Share Posted March 25, 2013 Here is the one i like cause i have wire and relays y spend more. http://m.summitracing.com/parts/prf-30110 Link to comment Share on other sites More sharing options...
ComancheKid45 Posted March 25, 2013 Share Posted March 25, 2013 Are we sure you don't have a burnt out fan motor? I mean if everything in the sensor circuit seems to be working hook the fan up to 12v and make sure it kicks on ;) Link to comment Share on other sites More sharing options...
ftpiercecracker1 Posted March 25, 2013 Author Share Posted March 25, 2013 Are we sure you don't have a burnt out fan motor? I mean if everything in the sensor circuit seems to be working hook the fan up to 12v and make sure it kicks on ;) I probably just need to replace the sensor, but i just wanted some reasurance. My electric fan is not wanting to turn on. I have let the truck warm up on two separate occasions, letting the needle just pass the last line before the orange/red zone and still no fan activity. I have tested the sensor, the one in the rad, in a pot of boiling water and it would appear to be working. Water starts to get a little bubbly and resistance drops to zero. I have also tested the circuitry, using a jumper wire i have connected the two wires that are in the sensor plug and the fan immediately kicks on and you can hear the relay click. Fan is new for all intents and purposes. T-stat is brand new, just put in a few hrs ago. Proper coolant level and bleeding have both been done. Lower radiator hose is getting very hot, so sensor is getting access to coolant flow. Since everything is working and fan still doesnt turn on my only conclusion is that the sensor is indeed bad, even though it would seem not to be. ftpiercecracker. fan is 100% fully fuctional. Question: Do all temp sensors used for electric fans work off the same priciples? Sensor is submerged in hot coolant, when temp gets hot enough sensor makes contact and allows current to flow. If so all I need to do is find a sensor that will fit in either the rad/t-stat and then make/buy a compatiable plug. Link to comment Share on other sites More sharing options...
Akula69 Posted March 25, 2013 Share Posted March 25, 2013 If you have A/C, does the fan come on when you turn the A/C on? The A/C bypasses the sensor and provides direct power to the fan. If it does not come on then there is a wiring/fan problem, if it does then the sensor is the culprit (or the wiring to the sensor). If it is the sensor, then generally they all work the same - the heat from the coolant closes the relay, allowing the current to run the fan. Some of the XJ/MJ have it mounted in a special fitting inline with the radiator hose (mostly the 86-87-88 years when present) the rest mount the sensor into a bung on the radiator tank. A good way to check the temps across the system is to use a infared thermometer, it can tell you the true temps at the tank (and by default, the sensor) to indicate if it should be activating. Link to comment Share on other sites More sharing options...
ftpiercecracker1 Posted March 25, 2013 Author Share Posted March 25, 2013 Yes the electric fan works with the a/c, but that is kind of irrelevant seeing that the fan works perfectly when a jumper wire is used to connect the two wires that are normally plugged into the sensor pig tail. I agree that a infared thermometer would help determine exactly what temp the rad is at. And i also agree that the sensor probably is FUBAR. I have a feeling that even though the sensor worked in the pot of boiling water it probably is not reading the coolant temp right. And i also had a brilliant idea for those that want to do dual eletric fans, but don't want a hard wired switch. Using the newer model T-stat housing with the sensor in it, you could cut the coniciding plug out of a JY vehicle and splice that into a secondary relay system to run your "first stage" E fan. Then when the temp of the coolant coming out of the engine reaches a certain point the first fan would kick on and the second fan would kick on when the coolant entering the engine reaches a certain temp. I will be doing this BTW. Link to comment Share on other sites More sharing options...
Akula69 Posted March 25, 2013 Share Posted March 25, 2013 Yes the electric fan works with the a/c, but that is kind of irrelevant seeing that the fan works perfectly when a jumper wire is used to connect the two wires that are normally plugged into the sensor pig tail. I agree that a infared thermometer would help determine exactly what temp the rad is at. And i also agree that the sensor probably is FUBAR. A jumper bypasses the wiring from the switch to the fan. Checking it with the A/C switch proves the wiring is good in that circuit. Pretty much narrows it to the sensor or the relay. Infared thermometers are cheap at HF (29.99 last I checked). Link to comment Share on other sites More sharing options...
ftpiercecracker1 Posted March 25, 2013 Author Share Posted March 25, 2013 Yes the electric fan works with the a/c, but that is kind of irrelevant seeing that the fan works perfectly when a jumper wire is used to connect the two wires that are normally plugged into the sensor pig tail. I agree that a infared thermometer would help determine exactly what temp the rad is at. And i also agree that the sensor probably is FUBAR. A jumper bypasses the wiring from the switch to the fan. Checking it with the A/C switch proves the wiring is good in that circuit. Pretty much narrows it to the sensor or the relay. Infared thermometers are cheap at HF (29.99 last I checked). Ok, and if it doesnt come on with the a/c? Keep in mind i have also tested the sensor with it in place, multimeter testing for ohms, they never changed from infinite even with the dash gauge reading 250*, contacts never made connection. Link to comment Share on other sites More sharing options...
ParadiseMJ Posted March 25, 2013 Share Posted March 25, 2013 Sensor closes at either 208* or 218*. . 6 degrees over a full boil at sea level Sensor closes at either 208* or 218*. I forget which one. I have the old sensor from the donor vehicle, its located in the T-stat housing. Has anyone adapted the Renix to work off this sensor? The "sensor" in the radiator is not a sensor...it's a switch. The sensor to the ECU is in the block. The sender to the gauge is a sender.The sensor in the t-stat on later models is a sensor. There was rumored to be a switch from a GM (Corvette IIRC) that could be used in the Renix 4.0 with a 91+ t-stat housing. But the normal 91 type Jeep sensor won't work for the switch . This is why I put my fan on a manual switch when I swapped radiators. I have a feeling that even though the sensor worked in the pot of boiling water ... Boiling is still 212F at sea level. Which is not 218F I'd have to agree with Cruiser, that it's just possible that there may be a lack of circulation at the switch in the rad...or scale...or devils with little pitchforks screwing things up!! Link to comment Share on other sites More sharing options...
ftpiercecracker1 Posted March 26, 2013 Author Share Posted March 26, 2013 Sensor closes at either 208* or 218*. . 6 degrees over a full boil at sea level > Sensor closes at either 208* or 218*. I forget which one. I have the old sensor from the donor vehicle, its located in the T-stat housing. Has anyone adapted the Renix to work off this sensor? The "sensor" in the radiator is not a sensor...it's a switch. The sensor to the ECU is in the block. The sender to the gauge is a sender.The sensor in the t-stat on later models is a sensor. There was rumored to be a switch from a GM (Corvette IIRC) that could be used in the Renix 4.0 with a 91+ t-stat housing. But the normal 91 type Jeep sensor won't work for the switch . This is why I put my fan on a manual switch when I swapped radiators. I have a feeling that even though the sensor worked in the pot of boiling water ... Boiling is still 212F at sea level. Which is not 218F I'd have to agree with Cruiser, that it's just possible that there may be a lack of circulation at the switch in the rad...or scale...or devils with little pitchforks screwing things up!! You wouldnt happen to know any more about that Corvette temp switch? I appreciate the info on the difference between a sensor and a switch. That has always got me confused. Do any of you know the thread size for the T-stat located jeep temp sensor? 3/8 NPT is what i have heard a lot of people saying and is there any way to distinguish between a sensor and a switch besides the boiling water test? P.S. the way to test a temp sensor is still the boiling water test, just turn up the ohms dial to 20K and you will get a reading, if the sensor is good. When dunked in hot water the ohms will rapidly decend. Link to comment Share on other sites More sharing options...
danbyrambler Posted March 26, 2013 Share Posted March 26, 2013 Didn't use teflon tape or anything on the temp switch threads did you? :hmm: Link to comment Share on other sites More sharing options...
ftpiercecracker1 Posted March 26, 2013 Author Share Posted March 26, 2013 Didn't use teflon tape or anything on the temp switch threads did you? :hmm: Sure didnt. And early some people were questioning if coolant was even reaching the sensor, i would figure it would have to be seeing that when i took it out half my coolant poured out. Link to comment Share on other sites More sharing options...
cruiser54 Posted March 26, 2013 Share Posted March 26, 2013 Didn't use teflon tape or anything on the temp switch threads did you? :hmm: The switch doesn't ground to the radiator. It has two wires. Cracker, got an IR laser type thermometer? Link to comment Share on other sites More sharing options...
ftpiercecracker1 Posted March 26, 2013 Author Share Posted March 26, 2013 Didn't use teflon tape or anything on the temp switch threads did you? :hmm: The switch doesn't ground to the radiator. It has two wires. Cracker, got an IR laser type thermometer? I wish. :( Link to comment Share on other sites More sharing options...
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