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coolant fans problem

10K views 71 replies 5 participants last post by  PONY MAN 
#1 ·
I’m unable to get my coolant fans to come on. I checked all related fuses and did relay swaps. I checked and topped off coolant. I can’t seem to pinpoint my issue. I’ve tried turning on my ac (which isn’t blowing cold either) but still no coolant fan action. I’ve went to engineer mode and let the car sit and idle (twice) to try and get the temp up but it’ll get up to 105 then gradually go back down. I tried one thing I remember doing in my other car and disconnected the coolant temp sensor then both fans automatically came on. I got a “SEE DEALER” warning but that assured me that the actual motor in the fans weren’t out. Could it be my thermostat even though I’m not overheating?? Any help, tips or suggestions would be greatly appreciated.
 
#2 ·
Grab a volt meter, looking for 12v starting at fan connector
 
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#3 ·
Let’s rule out the thermostat as part of the problem. Start the car cold and check to see if the coolant is moving in the rad. If it does the thermostat is stuck open and needs to be replaced. Now the engine can reach operating temp and see if the fans come on.
 
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#4 ·
Start the car. Let it run for a few minutes. Turn the heater to the highest temperature setting. Turn on the blower motor and see if the air is hot. By the way, one radiator fan should start soon after the air conditioner compressor is commanded on whether the air is cold or not. Presuming the power-train relay (R13) is functional, then check the emission 2 fuse (F32).

Pontiac G8 (2009) - fuse box diagram - Auto Genius
 

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#8 ·
The heater being hot indicates coolant is flowing throughout the system. Went back and read disconnecting the coolant temperature sensor wiring harness caused both fans to activate. As a result, can disregard the second half of post #4. Could be a faulty/erratic coolant temperature sensor since the temperature goes up to 105 and then falls. When the air conditioner is activated does the snowflake emblem's light remain lit (manual climate)? Remain lit or flicker on the screen (automatic climate)? Verified the refrigerant level?
 
#9 ·
I forgot to mention that after I got the coolant fans to turn on by unplugging the coolant temp sensor I immediately went to my parts store and picked one (CTS) m up and installed it in hopes of that being my problem. This morning I have replaced the thermostat and refilled with antifreeze and nothing has changed. It’ll get up to 105 then drop again from the engineer screen. I’ve checked the refrigerant with the parts store can/gauge (2 different ones) they both read that the system was “in the red” and I’m afraid to add any and mess something up further. The car isn’t over heating via the gauge but I’m unsure where else to check
 
#10 ·
Probably a moot point, but which brand of coolant temperature sensor was used? Thermostat? Have you inspected the coolant sensor's wiring harness? Be sure to properly bleed the system of air, Bleeding my cooling system of air. Per my understanding, those refill kits aren't very accurate and was thinking along the lines of checking the level (charge) with a professional set of gauges.
 
#11 ·
Probably a moot point, but which brand of coolant temperature sensor was used? Thermostat? Have you inspected the coolant sensor's wiring harness? Be sure to properly bleed the system of air, Bleeding my cooling system of air. Per my understanding, those refill kits aren't very accurate and was thinking along the lines of checking the level (charge) with a professional set of gauges.
Duralast on both parts. Inspected wires, they seem to be in good shape. I’ve bled/burped the coolant system real good. I’m just lost at this point. I’ll have to wait until tomorrow to have some professional gauges popped on the ac system. The most recent things done to the vehicle other than an oil change last month was 3.27 diff upgrade (Jan. 9th 2021) & headers plus full exhaust (April 30th 2020). I don’t drive it much because I want to keep it in as nice of condition as possible while continuing to mod it. I vaguely remember before winter having my ac blow warm on start up and then either after I toggled with it for awhile or after driving a little while it would begin to blow cool. I still don’t understand why my temp wouldn’t rise and fans kick on regardless of the ac... I really appreciate your help PONY MAN
 
#12 · (Edited)
Hears the deal >>>> There are 2 speeds for the engine cooling fans. Both fans run at low speed, or both run at high speed. To get those fans to even run at low speed, your engine coolant has to exceed 219 F and or the A/C has been commanded to run, an the high side pressure exceeds 220psi. The car will switch the fans over to high speed if the engine coolant temp were to continue to rise above 228 F , and or A/C high side pressure were to rise above 290 psi.
If your engines coolant system is so efficient that the temp never reaches that 219 F threshold or the A/C high side pressure never reaches 220 psi, those fans will not turn on unless you had some type of tuning done that would allow you to override those preset values. Since it reads like you cannot make cold air, an your engine coolant temp gauge apparently does not move up near the red zone, I can see why your fans never turn on.
If your positive your compressor belt is still spinning the compressor, my take is that you've lost most if not all of your refrigerant, or the electronic control valve in the compressor is not moving as it should to change the cold air demand requested (or worst case), the compressor took a dive on you. I ended up slowly loosing my refrigerant due to a leak from the high side pressure quick connect Shreader valve. An unless your staring at it (with the dust cap off) an see it bubbling, you would never know it was happening.
 
#13 ·
Hears the deal >>>> There are 2 speeds for the engine cooling fans. Both fans run at low speed, or both run at high speed. To get those fans to even run at low speed, your engine coolant has to exceed 219 F and or the A/C has been commanded to run, an the high side pressure exceeds 220psi. The car will switch the fans over to high speed if the engine coolant temp were to continue to rise above 228 F , and or A/C high side pressure were to rise above 290 psi.
If your engines coolant system is so efficient that the temp never reaches that 219 F threshold or the A/C high side pressure never reaches 220 psi, those fans will not turn on unless you had some type of tuning done that would allow you to override those preset values. Since it reads like you cannot make cold air, an your engine coolant temp gauge apparently does not move up near the red zone, I can see why your fans never turn on.
If your positive your compressor belt is still spinning the compressor, my take is that you've lost most if not all of your refridgerent (or worst case), the compressor took a dive on you. I ended up slowly loosing my refridgerent due to a leak from the high side pressure quick connect Shreader valve. An unless your staring at it (with the dust cap off) an see it bubbling, you would never know it was happening.
I’ve seen slight bubbling there before I believe. Is it on the driver side close to the radiator? It even has some black sutt around the valve as if it may have collected dust from leaking fluid. What was your the fix for the leak?
 
#14 · (Edited)
I bought a replacement Shreader valve for that high side pipe from O'reilys auto parts. I know they say it requires a special socket (8 sided or something like that ?) to remove an replace. But NO, you can easily replace it with a pair of vice-grips an a knuckle buster wrench. Then added about 15 oz of refrigerant an good to go. Not the right way to do it, but OK for know. Since I've had to bypass the steering cooling function of the condenser (due to leaking). I'll do it right when I change out the condenser. Can't bring myself to do it at this time since the A/C still works quite well. From memory, the part I bought was the Dorman valve # 800-955 for about $ 9
 
#15 ·
I bought a replacement Shreader valve for that high side pipe from O'reilys auto parts. I know they say it requires a special socket (8 sided or something like that ?) to remove an replace. But NO, you can easily replace it with a pair of vice-grips an monkey wrench. Then added about 15 oz of refrigerant an good to go. Not the right way to do it, but OK for know. Since I've had to bypass the steering cooling function of the condenser (due to leaking). I'll do it right when I change out the condenser. Can't bring myself to do it at this time since the A/C still works quite well. From memory, the part I bought was the Dorman valve # 800-955 for about $ 9
After replacing the valve did your low pressure side still read high? I’m trying to figure out how to recharge the system. I just add it to the low pressure side? At the moment it reads high
 
#16 ·
I'm not an expert with the A/C system, but these are the things I've read about an have seen with what little time I've messed with this stuff. If you have the A/C set that reads low an high psi at the same time, I can tell you that both sides should/will read the same based on ambient temp, an everything is at the same overall temp (as in the morning before the engine an A/C are fired up). With ambient temp of about 70 F the low side would be around 30 to 35 psi. A can of refrigerant will/can be drawn into the system, but works a lot better if the A/C is running If your static (or with A/C running) low side psi reading is a lot higher than above, I think that is an indication of some internal problem within the system.
 
#17 ·
Approximate air temperature? Does the temperature gauge start at cold and gradually increase before dropping? Was the car tuned after the headers installation? When the air conditioner is activated does the snowflake emblem's light remain lit (manual climate)? Remain lit or flicker on the screen (automatic climate)? By the way, correct operation of the coolant temperature sensor requires a good ground connection perchance to its mating surface. If so, the surface should be free of corrosion. Starting to wonder if there could be a shortage somewhere. :unsure:
 
#18 ·
Air temperature has been between 55-65 while working on it. Yes the temperature gauge starts low via needle and engineer mode then gradually rises up to only 105 then gradually drops back as low as 95 after running for approximately 15-20 mins. The car had rear O2s deleted and dod turned off but no performance “tune”. I’ve recently been getting an intermittent P0131& P0171 code as well. There’s no flickering of the snowflake after turning on ac I can’t remember if it was in manual or automatic. I’m still curious to know what my issue is but I dropped it off at the shop this morning feeling defeated because I haven’t been able to figure it out...😤 should know something in the next couple of days.
 
#20 ·
I’ve ordered some but initially I thought maybe it was an exhaust leak. Took it to a different exhaust shop than who did the header and we found a couple of spots that were slightly leaking. Patched em up and went about my business. Went about 3 days without the code again then it popped up this morning.
 
#23 ·
It says that IF the A/C pressure switch becomes faulty, it would display some info in the DIC an the HVAC/Radio face plate. I doubt that it is faulty. On your post stating 2 gauges showed low side pressure in the red, it tells me you have to much refridgerent in the system. I think you should bleed off some of it into a rag. See if you can get it to read in the 25 to 45 psi range (based on the current ambient temp). Until you post up the high an low pressures your getting from your A/C system when tested in the morning, as well as what those pressures are when its trying to make cold air, I see no way to assist on that system. If your engine coolant temp is ramping up to 220 deg F an an cycling back an forth, my mind says you have some air trapped in the system.
 
#25 ·
Very interesting. Does the coolant temperature gauge readout still fluctuate? Presume the radiator fan is engaging without the air conditioner compressor running, correct?
 
#26 ·
There’s no fix. They didn’t charge me anything and just allowed me to come pick it up. When I talked to them they just said they let the car run for awhile and they finally came on. It was only high speed. Ac still doesn’t blow cold. Nothing was done. It literally sat at the shop almost 2 weeks
Very interesting. Does the coolant temperature gauge readout still fluctuate? Presume the radiator fan is engaging without the air conditioner compressor running, correct?
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#27 ·
Since you.ve been told that your fans run at high speed (but only high speed) I want to say that your Fan 1 R17 cooling relay has a problem energizing. BUT IF that were true, you would also NOT be able to get that passenger side fan to run at high speed either. IF you think you can do a little T/S (with the ignition off), remove the R17 relay (located in the underhood fuse panel). Then correctly locate the 30 an 87 relay pin sockets in the base of that R17 relay, an jump those 2 positions with a wire or paperclip etc. That setup will/would command both fans to run at the low speed. If both fans now run at low speed, it must have been only the drivers side fan running at high speed (when it did come on for them). I think its more important to verify that both fans will run at the low an high speeds first, before zeroing in the the cause of the failed A/C.
 
#30 ·
Back to square one so to speak. May have been on to something in post #4. Be that as it may, swap relay R17 with another known to be working relay.
 
#32 ·
Do the fans operate normally while the vehicle is idling? Is the temperature hand stable? Can't believe the shop didn't verify the refrigerant charge. By the way, some aftermarket/generic relays are pretty finicky. Don't ask me how I know.
 
#33 ·
I didn’t let it get up to temp this evening given that it’s a colder evening tonight I didn’t even attempt it. Temp hand is steady and stable. I got a lifetime warranty on the relay I may try and swap for another if possible.
 
#36 ·
Great news for me!! This morning got the O2 sensor replaced so that code is gone (for now). Got the car up to temp and boom the low speed fans kicked in. I’m excited and THANK YOU all who chimed in and helped me with my process. I’m now going to make an appointment for the ac to be put on professional gauges.
 
#37 ·
Excellent. Truthfully, should have stuck with inital thought of going through the cooling schematic diagram two weeks or so ago. Suggest replacing the other upstream oxygen sensor as well. Are you going to another shop for the air conditioner or the same shop?
 
#40 ·
I now am all of a sudden as of yesterday hearing a rattle/tumble/ticking type of noise and it’s seemingly coming from the ac compressor. I drove it yesterday throughout the day since I’d been without the car and it’s still fairly cool outside. On average I only drive the car once every week and a half or so. I plan to enjoy it this summer though so I really need to figure out this ac issue
 
#41 ·
Yeah, summer temperatures can be brutal. Hopefully, the noise isn't coming from the air conditioner compressor which could certainly signify an issue(s). If the compressor was running, would turn off the air conditioner altogether until the system can be properly troubleshooted.
 
#42 ·
Welp I thought I had it figured out but a busted top radiator snout and overheating told me that I had not. Replaced the radiator and coolant and burped the system yet once again. Then took it for a test drive only for my temp to creep up past 105 with no more fan action. It got up to about 108 before I just shut it off in fear of another radiator accident. I’m really not sure where to turn from here
 
#43 ·
The upper radiator house outlet is a relatively "common" issue on the G8. Oftentimes, it simply blows right off the radiator likely due to a compromised snout. May be a good time to change the radiator cap with a genuine AcDelco unit. As a precautionary measure, will typically replace it along with the radiator. To help rule out a stuck thermostat, is the heater working properly? Can try post #27 again to rule out a defective relay. By the way, engine temp question..
 
#44 ·
The upper radiator house outlet is a relatively "common" issue on the G8. Oftentimes, it simply blows right off the radiator likely due to a compromised snout. May be a good time to change the radiator cap with a genuine AcDelco unit. As a precautionary measure, will typically replace it along with the radiator. To help rule out a stuck thermostat, is the heater working properly? Can try post #27 again to rule out a defective relay. By the way, engine temp question..
I tried the R17 pin swap this morning and sadly low speed did not come on like it did before
 
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