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Discussion Starter · #1 · (Edited)
I know this is one of those topics that has been beat to death with a stick (I read through every fan related post).

But anyway, my radiator fan seems to only operate at the highest speed. 10-20 seconds jet engine mode --> off --> repeat when it's hot outside. When I leave my car idling for awhile (I have to at one of my jobs), it will run on high speed until I'm back underway with some moving airflow, and that's with the AC off (I turn the AC off when it's parked, and don't even use it much in city driving).

Thing is, I have never observed my fan operating at a low speed. It's my understanding that it should be operating at low speed when the AC is on at least. From what I've read it could be:

-Faulty radiator fan unit (whole thing has to be replaced)
-Faulty thermostat
-Faulty coolant temperature gauge
-Faulty fan relay, if there is a replaceable one on the Cruze

Is there any way for me to troubleshoot this myself, or do I have to go to the dealer for diagnostics? Obviously my warranty is over, and I'm kinda worried they will just have me throw money at it, or tell me it's normal.

My coolant is topped off for sure, and I know the fluid is less than 3 years old, because the PO had a water pump replaced in 2014 at like 80K miles.
 

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This thing uses a bunch of relays (5 IIRC). What you might do is pull the resistor block off the fan and measure it. It's located in the upper right corner as you're bent over the radiator. I don't believe it's sold as a separate item. I think what happens is the fan becomes defective, draws too much current, and opens a fuse in that resistor block. End result, you lose low and medium speeds.

Since it's not sold separately, you have to replace the whole fan. (Which fixes the case of a bad fan.)

Off the top of my head, I think it's a 3 terminal device - you should have some resistance (less than a few hundred ohms) between any two terminals. If one is open, that's probably your problem.
 
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Discussion Starter · #3 ·
This thing uses a bunch of relays (5 IIRC). What you might do is pull the resistor block off the fan and measure it. It's located in the upper right corner as you're bent over the radiator. I don't believe it's sold as a separate item. I think what happens is the fan becomes defective, draws too much current, and opens a fuse in that resistor block. End result, you lose low and medium speeds.
Thanks, that kinda what I was thinking based on a couple other owners experience. I checked the block with a multimeter, and of course, it's labeled DO NOT REPAIR.

Guess I'll try this guy, and see what happens. Looks like replacing the fan assembly is straightforward enough.
 

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Guess I'll try this guy, and see what happens. Looks like replacing the fan assembly is straightforward enough.
Now that I see the backside, I know why it's not sold separately. It really is part of the fan assembly. I thought that was just a holder for it and the resistor pack comes out.
 

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My 2015 Cruze did the same thing for a short time. All I did was unhook both battery cables and then hold them together for 10 to 30 seconds, it should reset the system. Put the cables back on, roll the window up and down, and the problem was fixed for me. Could be a long shot for your situation, but a lot cheaper than replacing parts.

Sent from my SAMSUNG-SM-G890A using Tapatalk
 

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Off the top of my head, I think it's a 3 terminal device - you should have some resistance (less than a few hundred ohms) between any two terminals. If one is open, that's probably your problem.
Ok, the connector for the fan is 3-terminal - one for each speed. There's a separate ground connection somewhere. At least one fan terminal will have a low resistance to ground (or the fan wouldn't run at all). But if one of the other terminals are missing resistance to ground within a few hundred ohms or so, that speed is bad.

If you just measure between the terminals, you should show resistance between each one - but if they're bad, you won't have any.
 

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Considering all of the technology, it is interesting that they stayed old school on this fan. My 09 Vibe was PWM controlled with about 5 distinct speeds.
 

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Considering all of the technology, it is interesting that they stayed old school on this fan. My 09 Vibe was PWM controlled with about 5 distinct speeds.
I'm wondering who designed the fan relay system. 5 relays for a 3 speed fan. Part of that is because the BCM output is binary number - both outputs are high for "high speed", so they built a "and" gate in relay logic.

The downsize of a PWM is that it would have to be robust enough to handle defective fans and not cause any radio interference. I'm not saying it can't be done, but it does pose a bit of a design challenge - and gets expensive for the user if they get it wrong.
 

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Given that it's PWM, unless you've got a high quality RMS meter, it may not be doing a good job reading the effective voltage. However, it might be good enough to get an idea of what's happening.

Secondly, there's no guarantee that the voltage you're seeing is from the module - you might be seeing voltage generated by the fan as it windmills. You might want to consider a current probe instead.
 

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It was a simple DC average voltage measurement across motor supply. 0 volts when off, no voltage detected as a result of auto rotation. I was more concerned about temperatures and general speed steps comparison.

I would adjust the grill block throughout the season for momentary operation of the first or second fan speeds on level ground and to ensure that the highest speed was only on for a few second.

I have not seen any diagrams, but I have a feeling that Cruze uses two fields with a common ground IOT generate the three speeds. So your idea to measure current will be the way to evaluate the cut in and cut out temperatures, if they are actually consistent.

The Cruze also has a radiator return temperature sensor to the ECU, which is likely one of the many variables that the ECU used to manage the fan and the ECO shutter.
 

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I have not seen any diagrams, but I have a feeling that Cruze uses two fields with a common ground IOT generate the three speeds.
Coming out of the BCM, there are two lines. One for low speed, one for medium speed, and both for high.

The 5 fan relays change that into 3 wires going to the fan module: low, medium and high. (There's another wire somewhere for the ground return.) In the fan, the low and medium run though resistors and a thermal fuse. High is direct and bypasses the thermal fuse. I'm not quite sure where you'd monitor, but I'd give some thought to monitoring the current though the fan fuse. Otherwise, I think you're having to partially disassemble the fan to get to what really being fed to the fan motor (after the dropping resistors).
 

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Discussion Starter · #13 ·
Anyone replaced one of these fans + shroud without draining the coolant and removing the hoses? It looks to me like there's only two push tabs on the bottom brackets, then you just pull it out, but I figured I'd ask before trying to shortcut it, and breaking something.
 

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Anyone replaced one of these fans + shroud without draining the coolant and removing the hoses?
The manual doesn't call for opening the cooling system, but does call for removing the "front end upper tie bar". And the first step in that is to remove the front bumper fascia.

It does say that once you have everything ready, you should be able to slide the fan sideways, tilt it, and then take it out at an angle (as opposed to lifting straight up).
 

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This thing uses a bunch of relays (5 IIRC). What you might do is pull the resistor block off the fan and measure it. It's located in the upper right corner as you're bent over the radiator. I don't believe it's sold as a separate item. I think what happens is the fan becomes defective, draws too much current, and opens a fuse in that resistor block. End result, you lose low and medium speeds.

Since it's not sold separately, you have to replace the whole fan. (Which fixes the case of a bad fan.)

Off the top of my head, I think it's a 3 terminal device - you should have some resistance (less than a few hundred ohms) between any two terminals. If one is open, that's probably your problem.
would you happen to know the part numbers for the relays that control the cooling fan? I'm looking for the cooling fans relays here::

282996

282997


282998


282999

Text Font Line
Text Font Line Number Parallel
Text Font Line Number Parallel
Text Font Line Number Parallel
 

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Anyone replaced one of these fans + shroud without draining the coolant and removing the hoses? It looks to me like there's only two push tabs on the bottom brackets, then you just pull it out, but I figured I'd ask before trying to shortcut it, and breaking something.
Hey zen did replacing the fan fix everything? My fan only turns on high and not on low or medium.
 

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How do you check and where do you check for the resistors that control the engine cooling fan? Mine is always on high speed as well. All the relays were changed with no change to the fan speed
 

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How do you check and where do you check for the resistors that control the engine cooling fan? Mine is always on high speed as well. All the relays were changed with no change to the fan speed
This post has instructions for testing the fan to see if the resistors for LOW and MED are blown.

Doug

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