Fan clutch problems
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Fleet Mechanic
Joined: Feb 2018
Posts: 1,592
Likes: 204
Fan clutch problems
Anyone have problems with their fan clutch? There is a speed sensor in the clutch that sends the fan speed back to the PCM. The PCM sets a desired (setpoint) rpm, and a % load (or is it called duty?) is calculated on feedback from the difference between actual and desired. Anyway, I can see all this stuff in FORScan. Intermittently, the speed signal is lost and reads zero, forcing the % duty to 100%, which basically locks up the clutch and makes the truck sound like a prop plane. I’m under warranty and plan to take it in, just wanted to see if anyone else had any issues. It does not throw a code, or hasn’t yet. Thanks.
Posting Guru
Joined: Mar 2006
Posts: 1,275
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From: Long Island, NY
Yes I had a problem with my fan clutch with less than 500 miles on it. The entire assembly was replaced by the dealer for doing exactly what you were saying. The clutch was locked up and sounded ridiculous. We won't get into the fact that I actually had to go back to the dealer while my truck was there because they said there was nothing wrong.
Hotshot
Joined: Oct 2015
Posts: 19,698
Likes: 12,825
From: Wyoming
At least on my half ton truck the OEM clutch fan pulled a lot more air than the dual e-fans that I replaced it with.
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Laughing Gas
Joined: Dec 2005
Posts: 906
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From: Seattle area
It's a CFM capacity issue. While many vehicles use electric fans, they don't have quite the heat load that heavy duty trucks towing at low speed up long inclines produce. When the clutch engages and that thing speeds up to full speed, it is pushing a metric butt-ton (technical measurement) of air. The way to do that much work is to drive it directly off the motor, or install a much larger, heavier, and higher current draw electric motor. The highest flow dual-fan flex-a-lite fan I found pulls 6,200 cfm at 36 amps. The mechanical fan pulls around 14,000CFM (though I found varying reports from 10,000 to 20,000 - maybe someone will chime in with an actual Ford approved number).
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Elder User
Joined: Jun 2017
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General Messup tried electric fans on some D'maxes, I believe, those trucks had a history of overheating issues. I'm not trying to bash them so please someone correct me if I'm wrong, I thought we had one or two of them around here with electric fans. Overall, electric fans just can't pull the volumes of air needed to keep cool. Have yet to see one on a semi. That tells the story.
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Fleet Mechanic
Joined: Feb 2018
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It was basically locked up, so fan speed went up with engine speed. Get up to 2500 rpm and it's really humming. By intermittent, I mean that there were a few times when it acted totally normal, but mostly it stayed locked up.
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Fleet Mechanic
Joined: Feb 2018
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Back when I worked on Mustangs a lot, a common swap was to add a Lincoln electric fan to a Fox body mustang and eliminate the belt driven fan. It worked really well but it was loud. It also pulled a lot of amperage and was on/off. Plus, that engine didn't require the cooling a 6.7 does. I imagine you could do it with an electric fan, but it would be loud, draw a ton of current, and a variable speed drive that delivers that much current might get pretty expensive.
Tuned
Joined: Jul 2010
Posts: 408
Likes: 2
From: Canada
This is exactly what I've got happening with my 2018 - going into dealer beginning of April. Forscan gives me the exact same readings. At engine idle of 600 RPM, the fan speed is 825 RPM. But as soon as I step on it, the fan maxes at 3700 RPM and sounds like a jet engine. Pretty annoying.
