Coolant fan temperature sensor. I know, I know
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Racer
Joined: Aug 2014
Posts: 478
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From: Elizabethtown, NC
Coolant fan temperature sensor. I know, I know
I have a 1985 Z51 that I bought recently and was hearing the main puller fan run constantly.I woke up this morning and started looking into it. I started the engine and let it warm up and when the temp gauge got to 176 degrees the main puller fan came on. I then watched the temp gauge keep rising up and up. I kept feeling the upper radiator hose to feel when the thermostat opened and it did at 190 degrees. So I started saying to myself that the fan came on all the while trying to cool the engine even though the thermostat didn't open till 190 degrees. I then turned the engine off to let it cool down. I then pulled the wire on the temp sensor between cylinder 6 and 8. Started it up again to see what would happen. The main fan came on again at 179 with the wire off. I then pulled the wire of the temp switch between cylinder 1 and 3 and found the dash temp gauge went blank so I plugged it back in.
So what all of this tells me is that someone programed the ecu to run the fan at 176 . Also put a 190 degree thermostat in. None of this makes sense. I could understand changing the ecu to come on at 176 if you had a 160 thermostat or none at all maybe.
So what all of this tells me is that someone programed the ecu to run the fan at 176 . Also put a 190 degree thermostat in. None of this makes sense. I could understand changing the ecu to come on at 176 if you had a 160 thermostat or none at all maybe.
Last edited by dentalfloss; Dec 13, 2020 at 08:31 PM.
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My cars PO had replaced the coolant temp sending unit with the wrong part. Or it was wearing out but the ohms weren't correct for the temperature. My fan was showing to kick on at 170 but my oil temp was like 220. I changed out the sensor and the fan now shows to kick on at 220 or whatever. The temperature display on my dash was wrong.
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From: Overland Park Kansas
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Thread Starter
Racer
Joined: Aug 2014
Posts: 478
Likes: 66
From: Elizabethtown, NC
To follow up, I went out today to try and figure out what is making my cooling fan come on at such a low temp before my thermostat opens. I disconnected all three cooling sensor. The one in the intake manifold, the one on left cylinder head and the one on right cylinder head. I started the engine and let it warm up. The main puller fan came on as stated in my post above. This did not make any sense with all 3 sensors unpluged. The only thing I can think of is something is sending information to the fan relay to run the fan. Everything looks original with no wire tampering anywhere.
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From: Overland Park Kansas
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Originally Posted by GREGGPENN
If I were you, I'd follow the power/ground wires for the main fan to see where they lead. You might have an aftermarket fan controller.
Last edited by GREGGPENN; Dec 16, 2020 at 10:28 PM.
Thread Starter
Racer
Joined: Aug 2014
Posts: 478
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From: Elizabethtown, NC
Thank you all for responding with your suggestions. This is the temp sensor that goes to the ecm that I unplugged along with the other 2 as I mentioned. I am going to pull the ecm and check it out and see what prom is in there and go from there. It also could be a bad ecm. I may take your advise and buy a hypertech chip or order one from TPI chip programming if they still make them. I am still confused and think I honestly did the testing the way I explained twice. The second time the main fan came on at 160. How I tested with the 3 sensors unplugged was wait for the fan to come on and then plug in the sensor by # 1 plug and then checked the dash gauge. I deffinetly believe the dash gauge is reading correct because when the top radiator hose gets hot the temp gauge reads 190 and when I drive around it reads 190 give or take with a 190 stat. I do not want to install a 160-170 thermostat but will go with a 180 and I could always consider a sensor kit for that but first things first.
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Joined: Nov 2003
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From: Overland Park Kansas
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Well....summabeach. Thought I clicked "Quote" to bring my prior post forward. I removed all but the statement shown above. It was supposed to be THIS post!
Probably looked at the your post...which has the "Quote" button furthest to the left...popped up to mine and clicked the same button without reading! Sorry...but hopefully, you'd already read/absorbed what I said...before I accidentally removed most of it.
Anyway...trace your wiring and look for a fan controller. That's easier than dropping the ECM -- as a first step.
I have to add being curious how the ECM controls the fan -- if the CTS signal is broken. Reporting that you see turn-on at different temps is odd...no matter how it bypasses fan operation for another method. Guessing that 190 is your actual coolant temp isn't good diagnostics. They have a relatively cheap point and shoot thermometers these days. Plus, people have been known to find incorrect stats in a new installation. Plus, if you read that other thread I linked, you'll see more than one of us reported a discrepancy between ECM and dash temps....based on variances between the two sensors.
Maybe you could drop by your local auto mechanic and ask if he can point a temp guage at your hoses.
Probably looked at the your post...which has the "Quote" button furthest to the left...popped up to mine and clicked the same button without reading! Sorry...but hopefully, you'd already read/absorbed what I said...before I accidentally removed most of it.
Anyway...trace your wiring and look for a fan controller. That's easier than dropping the ECM -- as a first step.
I have to add being curious how the ECM controls the fan -- if the CTS signal is broken. Reporting that you see turn-on at different temps is odd...no matter how it bypasses fan operation for another method. Guessing that 190 is your actual coolant temp isn't good diagnostics. They have a relatively cheap point and shoot thermometers these days. Plus, people have been known to find incorrect stats in a new installation. Plus, if you read that other thread I linked, you'll see more than one of us reported a discrepancy between ECM and dash temps....based on variances between the two sensors.
Maybe you could drop by your local auto mechanic and ask if he can point a temp guage at your hoses.
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Thread Starter
Racer
Joined: Aug 2014
Posts: 478
Likes: 66
From: Elizabethtown, NC
Well....summabeach. Thought I clicked "Quote" to bring my prior post forward. I removed all but the statement shown above. It was supposed to be THIS post!
Probably looked at the your post...which has the "Quote" button furthest to the left...popped up to mine and clicked the same button without reading! Sorry...but hopefully, you'd already read/absorbed what I said...before I accidentally removed most of it.
Anyway...trace your wiring and look for a fan controller. That's easier than dropping the ECM -- as a first step.
I have to add being curious how the ECM controls the fan -- if the CTS signal is broken. Reporting that you see turn-on at different temps is odd...no matter how it bypasses fan operation for another method. Guessing that 190 is your actual coolant temp isn't good diagnostics. They have a relatively cheap point and shoot thermometers these days. Plus, people have been known to find incorrect stats in a new installation. Plus, if you read that other thread I linked, you'll see more than one of us reported a discrepancy between ECM and dash temps....based on variances between the two sensors.
Maybe you could drop by your local auto mechanic and ask if he can point a temp guage at your hoses.
Probably looked at the your post...which has the "Quote" button furthest to the left...popped up to mine and clicked the same button without reading! Sorry...but hopefully, you'd already read/absorbed what I said...before I accidentally removed most of it.
Anyway...trace your wiring and look for a fan controller. That's easier than dropping the ECM -- as a first step.
I have to add being curious how the ECM controls the fan -- if the CTS signal is broken. Reporting that you see turn-on at different temps is odd...no matter how it bypasses fan operation for another method. Guessing that 190 is your actual coolant temp isn't good diagnostics. They have a relatively cheap point and shoot thermometers these days. Plus, people have been known to find incorrect stats in a new installation. Plus, if you read that other thread I linked, you'll see more than one of us reported a discrepancy between ECM and dash temps....based on variances between the two sensors.
Maybe you could drop by your local auto mechanic and ask if he can point a temp guage at your hoses.