Fan speed
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Fleet Mechanic
Joined: Jul 2018
Posts: 1,629
Likes: 103
From: Jacksonville Florida
Fan speed
Here's what I run into today chasing a well pump. Running on the interstate ECT 192 Eot 201-2.
80 85 mph. Fan speed 650 +/-
All of a sudden I get off interstate and start the stop and go. Fan speed drops to 345+/- ECT 195. Eot 202 . and my a.c. got warm till took off again. Just caught my attention. I know I was cruseing???? What do y'all think.
80 85 mph. Fan speed 650 +/-
All of a sudden I get off interstate and start the stop and go. Fan speed drops to 345+/- ECT 195. Eot 202 . and my a.c. got warm till took off again. Just caught my attention. I know I was cruseing???? What do y'all think.
Tuned
Joined: Dec 2013
Posts: 399
Likes: 38
From: Rockport, TX
Mine does too. Drives me crazy.
I'll add that recently, my oil temp sender went out on me and immediately, my fan would lock up at 100% all the time no matter what speed or coolant temp. I'd be going 60 and the fan roaring, going 25 and the fan roaring. Best coolant temps my truck ever saw! I'm guessing that the PCM commanded the fan on since it had no reading from the oil temp sender. As soon as I replaced the temp sender, it went back to 'normal'. All this to say that I'm pretty sure my fan works when told to do so. But it does take a long time to kick on at low rpms after a running at higher speeds.
I'll add that recently, my oil temp sender went out on me and immediately, my fan would lock up at 100% all the time no matter what speed or coolant temp. I'd be going 60 and the fan roaring, going 25 and the fan roaring. Best coolant temps my truck ever saw! I'm guessing that the PCM commanded the fan on since it had no reading from the oil temp sender. As soon as I replaced the temp sender, it went back to 'normal'. All this to say that I'm pretty sure my fan works when told to do so. But it does take a long time to kick on at low rpms after a running at higher speeds.
Thread Starter
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Fleet Mechanic
Joined: Jul 2018
Posts: 1,629
Likes: 103
From: Jacksonville Florida
I think i read in a past post about your a.c. cutting of when motor hits certain temps. Also think it was upwards of 220° I'm trying to find that post but can't remember who started it. Does that sound Wright to y'all? I'm going to check my sensers today by swapping them. Nothing else to do. 
Fleet Mechanic
Joined: Sep 2006
Posts: 1,491
Likes: 295
From: Fresno, CA
Those numbers sound about right. My fan will lock up the clutch at idle during the summer with the AC going, fan speed gets up over 850rpm at idle. It will unlock once I get moving, sometimes if you hit the accelerator hard you can hear the fan for a brief second. I don't know the logic for that. I believe it is based off the AC high-side pressure. Pressure will generally go up once you stop moving due to lack of airflow.
Lead Driver
Joined: Dec 2006
Posts: 6,496
Likes: 94
From: So. Jersey
Sounds like the high pressure cutoff switch kicked in. With less airflow the temp will increase causing the pressure to also go up and if it hits that cutoff the compressor clutch is off until the pressure comes back down.
Postmaster
Joined: Sep 2016
Posts: 3,941
Likes: 240
From: Texas
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Cross-Country
Joined: Feb 2019
Posts: 56
Likes: 7
Here's a dumb, but somewhat related question- should I be seeing any fan speed during cranking?
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Thread Starter
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Fleet Mechanic
Joined: Jul 2018
Posts: 1,629
Likes: 103
From: Jacksonville Florida
I really don't pay attention on cranking, so me myself can't answer that. I will check it out here in about an hour. I'll let you know what mine does. Not to say that it is regular protocol.
Maybe one of the other guys knows the answer.
Maybe one of the other guys knows the answer.
Thread Starter
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Fleet Mechanic
Joined: Jul 2018
Posts: 1,629
Likes: 103
From: Jacksonville Florida
Well went to lunch.
I started torque Pro before cranking. Fan didn't register till after motor started. Then it shot to 800 and settled at 650 for about a minute then settled finally at 350. Don't know if that helps. That's just what my truck does, again not sure if that's the norm?
I started torque Pro before cranking. Fan didn't register till after motor started. Then it shot to 800 and settled at 650 for about a minute then settled finally at 350. Don't know if that helps. That's just what my truck does, again not sure if that's the norm?
Cross-Country
Joined: Feb 2019
Posts: 56
Likes: 7
Hmm, mine registers fan speed with engine cranking. I wonder if that's contributing to my harder starts in the mornings. The fan strategies seem to be more complicated than first glance. Don't want to go off tangent, but I do appreciate the double check.
Cargo Master
Joined: Oct 2018
Posts: 2,811
Likes: 1,911
From: unfortunately Germany
I was also happy with the 7.3 fan clutch, but at high outside temps in summer in traffic jams or when engine idled for a long time, the AC shut off. I have now switched to a snow plow clutch and installed the blue wire solution.
Fleet Mechanic
Joined: Sep 2006
Posts: 1,491
Likes: 295
From: Fresno, CA
I was also happy with the 7.3 fan clutch, but at high outside temps in summer in traffic jams or when engine idled for a long time, the AC shut off. I have now switched to a snow plow clutch and installed the blue wire solution.
https://youtu.be/dPZ5vQov0EI
https://youtu.be/dPZ5vQov0EI
Thread Starter
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Fleet Mechanic
Joined: Jul 2018
Posts: 1,629
Likes: 103
From: Jacksonville Florida
Do you think the blue wire on a switch would curb, but maybe not cure, the problem? I have summer coming up and am curious. (Fla) I have good #'s on the truck, but the AC has me a little worried. Already checked coolant and preasure and both are good. Driving the interstate will frost ya😂😂 . just curious !!