Cooling Fan Does NOT Turn ON! - Chevy Malibu Forum: Chevrolet Malibu Forums

ignaciodiego · 01-25-2009, 10:21 PM

i am working on a 2000 malibu V6. the cooling fans do not turn on and is causing the car to overheat. all relays and fuses have been checked for the fans, as well as checking the fans directly and still getting no response. I had someone tell me that the fans were wired into the a/c system, and that i should try checking out all of the a/c fuses and relays. i wanted to know if this was true or not. and also looking for any suggestions or if anyone has had this problem how did you resolve it??

BillD64 · 01-26-2009, 09:30 AM

Here is the schematic for the fans:

The PCM does the fan control. The PCM takes inputs from the AC system and the coolant temp sensor and determines when to turn on the fan.

Bill

ignaciodiego · 01-26-2009, 04:43 PM

Wow i really have to thank you for taking the time to put that diagram up!! i appreciate the help. couldnt have asked for better!

triplex-08 · 01-31-2009, 08:17 AM

you can jumper the relay to force the fan to turn on, supply it with ground, and you can test the fan. this will bypass the pcm, and on the other fan you can just jumper the terminals on the relay block and you should have fan operation, which will verify if your fans are good.

other than that, check your wiring from your pcm to the fan and from the fan to the relay and throughout the circuit, you can test all of this with a digital multimeter and a test light. easy to make a jumper wire, get a fuse holder from autozone or whatever, stick a 10 amp fuse in it or whatever the circuit has, then crimp some terminals on it, relay terminals are the same size as those terminals you get in a pack at the auto stores. just a simple blade terminal will work.

Malibu Glow · 01-31-2009, 08:36 AM

I think you should look at the coolant sensor first, always start at the easiest parts first before you dive head first into a nitemare! That's why service technicians check the obvious first, it's all a process of elimination when diagnosing a problem.

Oh and an EASIER WAY to check out between the PCM and the cooling fans would be to find someone with a laptop and a tuner that can hook into the cars OBD2 port then can run a diagnostic on the whole car. This alone will tell you continuity of the circuits if the PCM is receiving and sending signals.

triplex-08 · 01-31-2009, 10:56 PM

scan tool is only going to tell you so much, diagnosing why the fan isnt working is what we are trying to figure out. you can use a scan tool to figure out if it has a code, and a tech 2 to command the fan on, then if it doesnt work, then you take a test light to the connector for the fan, and if it lights between power and ground, you need a new fan.

sorry, i assumed he didnt have access to a tech 2.

Malibu Glow · 02-01-2009, 07:07 AM

I didn't say a damn scan tool. I said a LAPTOP and a TUNER, either DHP or HP tuner used with a laptop will do way more than a scan tool.

ignaciodiego · 02-01-2009, 10:22 AM

OK so far this is my update....the fans work with direct power. we have a scanner but no check engine light. We have changed the temp sensor which may or may not have helped but its changed. We found a leak in the intake manifold and are working on that repair. I will update as soon as we get that big job done. thanks for all of the suggestions you guys are a great help! I have to say this is one of the best forums for techincal/professional help and expertise.

ccarsten · 10-18-2009, 04:50 PM

Quote:

Originally Posted by BillD64

Here is the schematic for the fans:

The PCM does the fan control. The PCM takes inputs from the AC system and the coolant temp sensor and determines when to turn on the fan.

Bill

I have a similar issue with my '97. fan motors and relays are all goog and I just installed a new temp sensor. If the PCM is bad, where do I find it?

mike225 · 06-13-2011, 11:02 AM

Quote:

Originally Posted by BillD64

Here is the schematic for the fans:

The PCM does the fan control. The PCM takes inputs from the AC system and the coolant temp sensor and determines when to turn on the fan.

Bill

One step further in this path. My fans do not come on until it reaches about 230 DegF, then both come on as you would expect. If I turn on the AC the fans will come on. The fans primary fan will not come on by itself any earlier than that.

Another issue I'm having seems to be intermittent electrical issues, like the Theft System light coming on while I drive (it doesn't effect any operations it just lights up to be annoying), the Cruise Control will not engage at any speed, I have some black smoke when accelerating mild-to-hard.

I've had the injectors brought out and flow-checked and they are fine, now.

How would you go about testing the PCM directly? Or determine what parameters it's using to turn on.

Thanks,
Mike