Radiator Fans Not Running at Idle Overheating
01-28-2023, 10:21 AM
#1
Radiator Fans Not Running at Idle Overheating
Hello all,
My 2005 S2K started overheating at idle yesterday. I read some threads in the forum and learned that in some cases the fans will come on if the a/c is turned on. That is the case for me. What I wasn't able to determine clearly from the other threads is how to diagnosis the cause of the issue when this is the case. Any guidance would be greatly appreciated.
Also, coincidentally, this happened as I picked up my car from a repair shop that had just completed some body work on the trunk pan. During this work they diagnosed where a leak was coming from. I did not think any of this work would have required disconnecting the batter, but based on the clock on the dash, they appear to have disconnected the battery for some reason. Do you see anything here that would cause you to believe the two happenings are related?
Thanks!
My 2005 S2K started overheating at idle yesterday. I read some threads in the forum and learned that in some cases the fans will come on if the a/c is turned on. That is the case for me. What I wasn't able to determine clearly from the other threads is how to diagnosis the cause of the issue when this is the case. Any guidance would be greatly appreciated.
Also, coincidentally, this happened as I picked up my car from a repair shop that had just completed some body work on the trunk pan. During this work they diagnosed where a leak was coming from. I did not think any of this work would have required disconnecting the batter, but based on the clock on the dash, they appear to have disconnected the battery for some reason. Do you see anything here that would cause you to believe the two happenings are related?
Thanks!
01-28-2023, 12:04 PM
#2
Fans should turn on with the AC all cases. That they do in your case rules out the fans themselves.
Otherwise the fans are controlled by a thermal switch in the bottom section of the radiator next to where the lower hose connects. If the connectors are loose the fans won't run. Fairly easy to check. The switch actually trips a relay so if the switch is good check the relay. Jumpering the wires going into the thermal switch will confirm the wiring there is good. The switch is available. (Note 2006 and later cars have a sensor there as the fans are controlled by the ECU not a thermal switch.)
Chapter 10 in the Service Manual has details.
-- Chuck
Otherwise the fans are controlled by a thermal switch in the bottom section of the radiator next to where the lower hose connects. If the connectors are loose the fans won't run. Fairly easy to check. The switch actually trips a relay so if the switch is good check the relay. Jumpering the wires going into the thermal switch will confirm the wiring there is good. The switch is available. (Note 2006 and later cars have a sensor there as the fans are controlled by the ECU not a thermal switch.)
Chapter 10 in the Service Manual has details.
-- Chuck
Last edited by Chuck S; 01-28-2023 at 12:21 PM.
01-29-2023, 11:42 AM
#3
Chuck,
Thank you for the awesome reply. The Service Manual link is also fantastic. I am a bit limited on my understanding of electrical and how to test some of the things they are saying should be tested. I have checked all fuses and they appear to be good. I jumped the relay and the passenger side fan immediately turns on when up to temp, but both fans run when A/C is on. I then noticed that the other relays next to it appear to be the same exact part. So I switched the clutch relay into the radiator fan relay spot, but it did not work. I put the jumper back in the spot and it worked.
First question, why does only the passenger side fan come on? Is that to be expected?
Second question, why didn't the fan work when I substituted the other relay for it? Does that point to a problem other than the relay?
Thanks very much for the help you have given me and so many other people you respond to on the forum!
Mark
Thank you for the awesome reply. The Service Manual link is also fantastic. I am a bit limited on my understanding of electrical and how to test some of the things they are saying should be tested. I have checked all fuses and they appear to be good. I jumped the relay and the passenger side fan immediately turns on when up to temp, but both fans run when A/C is on. I then noticed that the other relays next to it appear to be the same exact part. So I switched the clutch relay into the radiator fan relay spot, but it did not work. I put the jumper back in the spot and it worked.
First question, why does only the passenger side fan come on? Is that to be expected?
Second question, why didn't the fan work when I substituted the other relay for it? Does that point to a problem other than the relay?
Thanks very much for the help you have given me and so many other people you respond to on the forum!
Mark
Last edited by Slowgoing; 01-29-2023 at 12:08 PM.
01-30-2023, 05:36 AM
#4
To my recollection there is a difference in fan operation between the pre- and post-2006 cars. On my 2006 (DBW) car where the fans are controlled by the ECU it's either both or no fans. Earlier cars like your 2005 may only run a single fan unless the AC is on. Note there are separate 00-05 and 06-08 trouble shooting procedures for the fans.
Hopefully someone can confirm my recollection that a single fan does not run in the '06 and later -- both or none is my recollection.
-- Chuck
Hopefully someone can confirm my recollection that a single fan does not run in the '06 and later -- both or none is my recollection.
-- Chuck
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