Replacing the OEM cooling fan with an aftermarket cooling fan.

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Junior Member
Jan 29, 2024
Reaction score
North Carolina
Ram Year
Hemi 5.7
I have a 2019 5th gen Big Horn 1500 with the Hemi 5.7L. I purchased it in Oct. of 2022. I haven't had any issues with it untill recently. Of course I haven't had it but a little over a year now and here's the story with the cooling fan... A couple months ago while driving it I noticed the cooling fan running at high speed and the temp gauge was reading normal. The cooling fan was acting like the truck was overheating but, the temp guage on the cluster was reading normal so, I thought that the fan was going bad. I decided to purchase an aftermarket cooling fan and installed it. It was pretty easy to replace but, even with the new fan installed it, was still running at high speed. Then the check engine light came on. I ran a diagnostic on the truck with my OBD2 tool and it gave me a Evaporative Systems code. I don't remember the exact code but, it was around the 408 code I think.. So I was thinking about bringing it in when I decided to check the antifreeze level and condition of it. It was dirty and the reservoir tank was really low so, I checked the radiator by removing the cap and it was full but, dirty. So I decided myself that it needed a radiator flush so, I proceeded to do just that. I bought 8 gallons of distilled water and the best antifreeze I could find and started to flush the system. After the first flushing of 4 flushings the check engine light went out. Go figure. After the first flushing the check engine light went out and the aftermarket fan was running like an OEM fan should be. It was coming on only after the engine came up to temp and went off when the system went cool telling me that the thermostat was doing its job and the computer was telling it to shut off when at its cool point, or what ever you call it.
I ran the truck 2 times after this and the second time I smelled coolant while I was driving it.. once I got home I then lifted the truck to see if the coolant was leaking and it was. It was leaking from the water pump so, I decided to take make an appointment with the dealership to get the water pump replaced. The morning I was going to bring it in the temperature was around 20 degrees F. and when I cranked the truck up the check engine light was on again.... Go Figure! I took it in anyway without putting the diagnostic tool in it to see exactly why the check engine light was on again because of time constraints. Anyways... The service dept. told me that yes the water pump was leaking because of the seals and, that the aftermarket coolant fan I replaced the original with was why the check engine light came on but, it was working like it should be when I brought the truck in for servicing. I heard it working normally when I was driving it to the shop and I heard it working normally working when I shut the truck down when I got to the shop.
I want to know why the shop said that the aftermarket coolant fan was why the check engine light came on even though the aftermarket fan was doing its job.