Cooling fans wont come on automatically
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3 Posts
2006 LT 3.5
202,982 original miles ?
Hi Jon,
I don't know if you got your fans going or not, hopefully you have. But since no one has answered you I thought Id share what I have done with my same problem.
Mine are caused by wiring issues for the relays at the pcm. For now, this is a temporary fix, but I just direct wired my fans to kick on. There's lots of different ways you can do this. You can research on you tube.
I would suggest before that route check your relays and fuses.
There are some really good you tube videos on how to check for a bad relay/fuse/circuit also on you tube. The tools for checking are very inexpensive.
Digital multi meter and a test light. Both these you can get for under 5.00.
If you need any links or anything let me know.
Im not a mechanic but I do ALL my own work on my Malibu since day one. There may be better suggestions but something is better then nothing.
Bre
202,982 original miles ?
Hi Jon,
I don't know if you got your fans going or not, hopefully you have. But since no one has answered you I thought Id share what I have done with my same problem.
Mine are caused by wiring issues for the relays at the pcm. For now, this is a temporary fix, but I just direct wired my fans to kick on. There's lots of different ways you can do this. You can research on you tube.
I would suggest before that route check your relays and fuses.
There are some really good you tube videos on how to check for a bad relay/fuse/circuit also on you tube. The tools for checking are very inexpensive.
Digital multi meter and a test light. Both these you can get for under 5.00.
If you need any links or anything let me know.
Im not a mechanic but I do ALL my own work on my Malibu since day one. There may be better suggestions but something is better then nothing.
Bre
Joined
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3 Posts
Sorry, I need to let you know the wiring problem to relays isn't at pcm. It is the housing where the fuses and relays are under the hood by the pcm.
I thought about my wording and figured I should correct it. Sorry about that.
Bre
Joined
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3 Posts
I just discovered this issue with mine....noticed the temp gauge creeping past it's usual resting spot so I activated the a/c and heard the fan(s) come on and the gauges needle returned to it's usual place...I will be "swapping" relays around to see if that's the issue then moving on to Bre's suggestions...
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6 Posts
Has anyone come to a more conclusive resolution on this issue?? I am having the exact same issue with my 2006 Chevy Malibu LTZ v6 3.5L.
My cooling fans DO work; If I turn my a/c on, the fans will come on. I've already checked all of the relays & fuses, replaced the thermostat, replaced the temperature sensor, flushed & bled the system repeatedly.. I am at my wits end on this.
I've had it to a mechanic shop twice now & they were unable to turn up any useful conclusions. My radiator cooling fans simply do not come on at any point even when the temperature gauge surpasses the mid-line operating temperature.
Any assistance on this would be profoundly appreciated.
My cooling fans DO work; If I turn my a/c on, the fans will come on. I've already checked all of the relays & fuses, replaced the thermostat, replaced the temperature sensor, flushed & bled the system repeatedly.. I am at my wits end on this.
I've had it to a mechanic shop twice now & they were unable to turn up any useful conclusions. My radiator cooling fans simply do not come on at any point even when the temperature gauge surpasses the mid-line operating temperature.
Any assistance on this would be profoundly appreciated.
Get a scanner that lets you view live data, such as the BlueDriver, and watch your temps in real time. Compare that to the dash gauge, then determine if there's an issue with the fans turning on or not. It's possible that there really is no issue with the coolant.
The t-stat needs to be removed and checked in a pan of boiling water with a thermometer to see when it starts to open and when it's fully open. If it opens too late or doesn't open, then it needs to be replaced.
Also, check reference manuals so you know when the fans are supposed to turn on. They usually aren't needed when you're moving above a certain speed because there's already enough air passing over the radiator.
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6 Posts
Thank you very much for your responses, wasn't sure I'd be getting any being that these posts are quite old.
I took your advice &ordered an OBDII scanner. (Long overdue purchase anyhow, especially considering their affordability now.) I ran the vehicle in park, at idle for approximately 20 mins.(ambient air is quite cool today) in which it reached a coolant temp of 222.8°F with the gauge reading just below red. I turned my A/C on (as this still permits the cooling fans to activate) before allowing it to get any worse.
I haven't been able to locate an exact answer on what temperature the cooling fans are supposed to kick on at what speeds, but I've seen varying answers from 200-230°. I've always understood mid-line on the temperature gauge on the dash to be "operating temperature" which registered as 190° F on the scanner; so I'd imagine the answer for when the fans should kick on would be about 200-210°F tops if 230°F has the gauge almost in the red.
So with electrical continuity throughout the system (the fans both work with A/C on) a new temperature sensor, all fuses and relays checked- would this just come down to a BCM/signal issue? There is also a relay calling "Cooling Fan Ser/Par" (series/parallel) that I did test, and it did appear to function when placing 12v across it; but I am also unsure how exactly it's supposed to function or if it could still be the culprit. I haven't been able to find much info on it though.
The only code I got was a "P1258" code which is defined as an "Engine Coolant OverTemperature Protection Mode" that does something with fuel injection to mitigate heat in an overheating event (probably from when it overheated) but obviously wouldn't prohibit cooling fan activation.
So I'm really kind of at a loss for what to do other than replace that relay that as far as I could tell, is functioning properly.. otherwise it's a computing issue?
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6 Posts
Found a little more info on the ser/par relay. Essentially just switches the fan circuits from series to parallel for low and high speeds respectively. When I turn on my A/C to force the fans on in "high speed" mode (essentially parallel'ing cool fan 1/cool fan 2 relays) I am able to remove& reinsert the ser/par relay& physically ensure that it is functioning; thus it is not the culprit, either.
As I've said, my coolant sensor is also brand new. If it weren't functioning at all or was incorrectly replaced I would A) not be getting a dashboard reading on the temperature gauge & B) my fans would (and do) activate in "high speed mode" as a failsafe if the coolant sensor is not being detected. So the coolant sensor is brand new and is functioning properly as far as I am able to tell given these parameters to go off of.
I am not receiving a "low coolant" code or message on the DIC (driver info console). The system has been repeatedly bled for air blockage. The thermostat is brand new. The heater core is bypassed currently (just to rule out blockage in the core)
So again, is the only possible variable that remains a computer/BCM/signal issue that would likely require a tuner to diagnose or repair/correct? If there's anything else I can do that you can think of please let me know, as I do not have much confidence in any shop mechanics that I've been to in my area.. They've done nothing but take my money with no results already.
Thanks again!!
As I've said, my coolant sensor is also brand new. If it weren't functioning at all or was incorrectly replaced I would A) not be getting a dashboard reading on the temperature gauge & B) my fans would (and do) activate in "high speed mode" as a failsafe if the coolant sensor is not being detected. So the coolant sensor is brand new and is functioning properly as far as I am able to tell given these parameters to go off of.
I am not receiving a "low coolant" code or message on the DIC (driver info console). The system has been repeatedly bled for air blockage. The thermostat is brand new. The heater core is bypassed currently (just to rule out blockage in the core)
So again, is the only possible variable that remains a computer/BCM/signal issue that would likely require a tuner to diagnose or repair/correct? If there's anything else I can do that you can think of please let me know, as I do not have much confidence in any shop mechanics that I've been to in my area.. They've done nothing but take my money with no results already.
Thanks again!!
What would be good to know, like you said, is the temp at which the BCM / ECM commands the fans to turn on in series (slow speed) and when in parallel (high speed). You already know that parallel works, but there is a 5th contact when in series. If it's not able to make contact (burnt, bent, etc.) then they won't turn on for slow speed at all. Find another 5-pin relay elsewhere in the fuse box and swap it in for a test. Make sure it's not from a more critical circuit, though!
All of the 4-pin relays can be rotated 180° and work just fine, but the 5-pin cannot.
All of the 4-pin relays can be rotated 180° and work just fine, but the 5-pin cannot.
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Yeah I haven't been able to locate that information specifically, one forum post I saw claimed it was 223°F low speed/230° high speed; which I can't say for sure is incorrect.. but I'd imagine it isn't very accurate being that my gauge is just below red when at 230°.. & when my car was functioning correctly, it certainly never rose to that high of a temperature on the gauge before cooling off - is why I find that answer to be incorrect.
When at mid-line on the temperature gauge, my temperature is about 200° even, every so often it would rise just above that point before immediately coming back down (prior to these cooling issues) which leads me to believe from experience driving the car + what makes sense that 210° is probably the setpoint for high-speed fan signal.
At any rate, from a broad picture perspective: the vehicle is pinging damn near the red zone on the temperature gauge when just idling, and will (has) overheat(ed) only a couple of minutes into driving it. At no point do the fans come on when approaching overheat or even the times after it had, and I shut the engine off as soon as I could pull over safely, the fans still weren't on.
It took a while to realize this due to other symptomatic issues that have since been addressed, but now it seems the only issue (and possibly the original cause for the other issues that have been addressed) is the cooling fans not coming on at any point other than being commanded on by the A/C control circuit.
I will certainly be looking more into the 5 pin see/par relay for functionality- but again it did appear to have been functioning when I pulled it in& out while being commanded on by the A/C being turned on; as I pulled it in/out the relay would engage/disengage and the fans would also turn on/off as I did so.
I thank you again tremendously for your time and responsiveness on this!! I'll update with any further progress or information as I am able to (if I am able to..😜 that has been an ongoing issue for a couple of months now..)
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6 Posts
Hey there again, sorry for the lengthy posts I'm quite a long-winded individual 😆
Anyway, for the purpose of getting my car back on the road& until I am able to afford any further shop maintenance beyond my capacity, I figured I'd give an auxiliary fan control unit a shot (as discussed in the other thread I originally posted in). As far as I am able to tell this is a PCM/BCM signal issue that I lack the knowledge on how to rectify at this time. Everything I have been able to mechanically/electrically access& troubleshoot appears to be in good working condition: relays, fuses, coolant sensor, thermostat, pump, leaks, and coolant level have all been assessed. The system has been flushed/bled for air.. I'm at my wit's end.
I've never used or installed one before though, so if you have any recommendations or tips on the install or things to be aware of when going this route I'd be very appreciative.
Thanks again for your help with this, people such as yourself willing to take the time with people like me on forums truly are heroes. 😁
I have a 2004 SUV that I modified. The clutch fan is now history and it has 2 electric fans. There is an adapter that I added to the upper radiator hose that has a threaded hole for a temp sensor. That sensor goes to 2 switches (for me) and then to 2 fused relays to operate the fans. You'll need to get the size of your rad hose if you want to get one of these.
AmazonSmile: Black Aluminum Water Temp Meter Temperature Gauge Joint Pipe Radiator Sensor Adaptor Attachment Hose Clamps 36mm : Automotive
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