Car overheats with the A/C on?

Tiny
CHARLIE SANDOVAL
  • MEMBER
  • 2008 SATURN VUE
  • 3.6L
  • V6
  • 4WD
  • AUTOMATIC
  • 243,000 MILES
I checked cooling fan with Battery 12v ok, checked temperature sensor with Multimeter reading 2000 ohms cold and around 500 ohms hot assume this is okay. Would my problem be my thermostat?
Sunday, April 20th, 2025 AT 11:36 AM

13 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 51,853 POSTS
When the A/C is on and the engine is running does the cooling fan operate? If not, this will be the problem. The fan must run while the AC is on. If it does run then I would make sure the coolant level is full, (engine cold only) and if so, check for blockage at the radiator, either internally or externally.

Here is a guide that can help:

https://www.2carpros.com/articles/engine-overheating-or-running-hot

If the engine overheats in the first 15 minutes of driving, then I would suspect the thermostat. Here is the location so you can check it out. Check out the images (below). Please let us know what happens.

Image (Click to make bigger)
Thumb
Was this
answer
helpful?
Yes
No
Monday, April 21st, 2025 AT 11:23 AM
Tiny
CHARLIE SANDOVAL
  • MEMBER
  • 8 POSTS
Nether cooling fan was operating whether the A/C is on or off. Drove car this morning for 30-minute ride check the fans while car was idling nether one was on and not overheating had aircon fuse pulled during this test ride. Why are the cooling fans off?
Was this
answer
helpful?
Yes
No
Tuesday, April 22nd, 2025 AT 3:13 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 51,853 POSTS
Yep, that will do it. The cooling fans must run with the A/C on. There are three relays and 2 fuses that run the system. Let's see if the FAN MAIN fuse and the FAN AUX fuse are good and have power to them, (key on). The fuses are in the fuse panel under the hood.

This guide can help:

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

Please go over this guide and get back to us.
Was this
answer
helpful?
Yes
No
Wednesday, April 23rd, 2025 AT 9:14 AM
Tiny
CHARLIE SANDOVAL
  • MEMBER
  • 8 POSTS
Checked both MAIN and AUX fuses under the hood both have power. Did test with A/C disconnected.
Was this
answer
helpful?
Yes
No
Wednesday, April 23rd, 2025 AT 2:11 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 51,853 POSTS
You could have two fan motors that are bad, let try checking the ltblu and gray wires for power when the engine is running and the A/C on.

Here is a guide to help:

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

Please go over this guide and get back to us.
Was this
answer
helpful?
Yes
No
Thursday, April 24th, 2025 AT 8:34 AM
Tiny
CHARLIE SANDOVAL
  • MEMBER
  • 8 POSTS
Checked LTBLU and Gray wire no power. Found 15amp ENG-3 fuse blown, replace it and blew again right away? What does this fuse control? Fans were tested with 12V Battery and both work just fine.
Was this
answer
helpful?
Yes
No
Friday, April 25th, 2025 AT 1:48 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 51,853 POSTS
Did you check the fan circuit grounds? Here is what the ENG 3 fuse powers, nothing to do with the fans so please start a new thread for this problem.

Evaporative Emissions (EVAP) Canister Purge Solenoid Valve, Heated Oxygen Sensors (HO2S), Mass Air Flow (MAF) Intake Air Temperature (IAT) Sensor

Here is the wiring diagrams for the radiator cooling fans, I would swap the relays out one at a time to see if that is the problem. Check out the images (below). Please let us know what happens.
Image (Click to make bigger)
Thumb
Was this
answer
helpful?
Yes
No
Sunday, April 27th, 2025 AT 11:47 AM
Tiny
CHARLIE SANDOVAL
  • MEMBER
  • 8 POSTS
How do you check the fan circuit ground with a test light?
Was this
answer
helpful?
Yes
No
Tuesday, April 29th, 2025 AT 2:44 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 51,853 POSTS
Did you go over the guide? You put the ground lead of the test light on power.
Was this
answer
helpful?
Yes
No
Wednesday, April 30th, 2025 AT 10:36 AM
Tiny
CHARLIE SANDOVAL
  • MEMBER
  • 8 POSTS
Yes, I went over the guide. Thank you, what I don't know is where to check the fan circuit with the tester? That's where I need help.
Was this
answer
helpful?
Yes
No
Wednesday, April 30th, 2025 AT 11:01 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 51,853 POSTS
Gotcha, Remove the electrical connector from the right fan motor and check the black wire. Let me know.
Was this
answer
helpful?
Yes
No
Wednesday, April 30th, 2025 AT 11:04 AM
Tiny
CHARLIE SANDOVAL
  • MEMBER
  • 8 POSTS
No ground to the Right fan connector, had ground to the left fan connector.
Was this
answer
helpful?
Yes
No
Wednesday, April 30th, 2025 AT 1:44 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 51,853 POSTS
Okay, it sounds like you tested everything, so the PCM might be bad, let's run the codes to see which ones are stored.

Here is a guide to help:

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Please go over this guide and get back to us.
Was this
answer
helpful?
Yes
No
Thursday, May 1st, 2025 AT 9:47 AM

Please login or register to post a reply.

Related Engine Overheat Content

Is Your Engine Cool Enough to Check?
VIDEO
Is Your Engine Cool Enough to Check?
In­struc­tional re­pair video
Overheating Symptoms
GUIDE
Overheating Symptoms
An over­heat­ing en­gine is never a good thing to have hap­pen. If the prob­lem is caught quickly you can save the headache of a ma­jor en­gine re­pair. Know­ing the in­for­ma­tion from...
VIEW MORE