So we’re back trying to figure out why my parents CTS A/C system is blowing intermittently warm air. Now, if this was the only issue, you’d probably try to diagnose the A/C system first. However, given the initial issue with the auxiliary water pump and the SES light, I’m going to maintain my focus on the cooling system.

Parts for this DIY:

  • New Radiator Fan Motor
  • New Coolant Temperature Sensor (Optional)
  • Radiator Fluid (Optional)

 Tools You’ll Need:

  • A Ratchet Set
  • A Screwdriver Set
  • A Wrench Set

As you know the problem started a few weeks back when my parents were driving over to visit. They saw an SES light, warm A/C and slight operating temperature spike. Since we already fixed the root cause of the SES light, I started with a quick visual inspection (an ocular pat-down if you will). Immediately I noticed that with the A/C on, the radiator fan was not spinning. As a reminder, the radiator fan will turn on once the car reaches operating temperature. It will then cycle on and off as needed based on the thermostat. If your A/C system is on though, the fan should be at full speed all the time. If not you’re just going to get a blast of warm air.

With the radiator fan the CTS is directly behind the passenger headlight. In order to access the fuse/relay panel, you’ll have to remove the plastic engine shrouds. At this point if you take one off you should just take them all off from the engine, just to make life easier.

Once you’ve located the relay, you first need to check and see if it’s receiving an “on” signal. Remember that a relay is basically a bridge for the current flowing to the device in question. If the bridge is open, then the device won’t turn on. When the bridge receives the “on” signal, it closes to let the current flow through. This “on” signal is sent through the “86” terminal. The terminals are not marked on the panel, but they are on the actual relay. Just flip it over and see which one is which. To check if the signal is coming through you want to use your voltmeter and place the positive in the “86” terminal and the negative to a ground in the car. If the car is sending the signal to turn on the fan, you’ll see a positive voltage reading here. For the CTS, I saw about 14 volts, so that good.

Next we can test to see if the fan motor is actually working. We can do this by forcing the relay bridge to close. You’ll want to connect the “30” terminal and the “87” terminal with either a piece of electrical wire, or as I did, using the unfused connection on your voltmeter. By forcing the bridge closed the fan should turn on, regardless if the relay is damaged or if it is not receiving a signal from the car. In my case, the fan did not turn on, confirming the initial diagnosis of a burnt out fan motor.

Searching around a bit online I found the fan motor in question on Luckily you can purchase just the motor making it more affordable. I had checked Amazon too, but hadn’t found anything using the “2009 CTS fan motor” search criteria. Just in case though I checked using the part number on Rockauto (ACDelco 15-81137 GM Original Equipment Engine Cooling Fan Motor), and ding, ding, ding! $10 cheaper and free shipping. If you haven’t noticed, I love Amazon… Two days later the fan had arrived so it was time to get to work.

Much like the auxiliary pump, you’ll want to start off with all the engine shrouds removed. At this point I noticed that the air intake would be in the way. This is removed by loosening the coupling at the throttle body (flat-head screwdriver), and removing the air filter lid (three allen screws). Don’t ask me why they use allen type screws; I swear they do it just to intimidate shade tree mechanics. You can then unplug the MAF sensor, which is attached to the lid, and the smaller air inlet on the intake pipe. After pulling the assembly out, the radiator area really opens up.

There’re a couple more items you’ll need to remove before pulling out the fan. You’ll need to:
1. Unplug the radiator fan (top plug)
2. Disconnect the auxiliary water pump from the radiator fan housing (pop it off with a screwdriver)
3. Pop off the transmission fluid line from the supplemental bracket on the radiator fan shroud

That last one is a little tricky as you want to pop it loose, but you won’t really remove it as it is a hard line. With those items out of the way, we can loosen up the actual fan shroud.

The shroud is held in place with four (4) 10mm bolts, two on each side. The top driver side bolt and both passenger side bolts should be easily accessible with a small extension and a pair of small hands. My hands, while not huge, are nowhere close to being slender, as such I struggle a bit. But the bolts are very doable. The lower driver side bolt is the trickiest. It is located just below the supplemental bracket for the transmission coolant line that we popped off earlier. As such, there is no line of sight, so you’ll have to feel around a bit. There’s just enough space to squeeze in the drive socket, so worst case is you’ll drop the screw after loosening it and you’ll have to fish around for it. No biggie…

With the fan shroud loose you can just slide it out by the top. Now, it’s not going to be a smooth process, you’ll have to jiggle and squeeze left and right to get it to pop out. Pay particular attention to the coolant lines on the driver’s side, as they can get stuck. If you crack one of the tabs by the coolant lines it’s not the end of the world. They’re not really super necessary; they just need to make sure the lines stay in place. Ultimately though, there’s nothing else to remove and the radiator fan shroud should come out if you work carefully.

With the fan shroud on the ground, we can get to work on replacing the actual motor. First, disconnect the electrical connector going directly to the fan. This is a simple push tab connector.

Next you need to loosen up the actual fan blade, as it is bolted with a hex nut to the motor. This came off easily with a drive socket. Lastly, there are three phillips head screws that hold the fan in place. In my case the screws were really, really hard to get off… So much so that I stripped one of the screws. So, out came the drill and off came the screw head. With any luck you won’t have to go through this, but crap happens.

From here on out, just reverse the steps. Install the motor using the provided new screws. Install the blade and reconnect the plug. Drop the shroud back into place, carefully… Install the four bolts that hold it in place (finger tight first while you get them all in, then tighten). I’m sure there’s a torque setting for these somewhere, but I just used common sense. Reinstall the air intake assembly. Plug in the fan harness and auxiliary pump. And lastly, install the shrouds. You’ll put it together in a fraction of the time it took to remove.

There’s nothing left now but to test it. So I cranked the CTS over and turned on the A/C. I was greeted with a constant and steady stream of frigid air; so far so good… For confirmation I visually double checked that the fan was working and sure enough it was spinning away. Btw, always be careful with fans. Nobody wants to lose the tip of a finger by being careless. Success all around!

Hopefully, this will be the last we see of the CTS for some time.

Useful Parts & Tools to Help you with this DIY Project: