96 FLD 120 / 12.7 S60 Fan Always On

Hello all,

Hoping to get some assistance here. I’ve looked at about 10 previous posts and around Google for solutions. I recently did some work to my truck by myself (so no shops involved) and the engine fan is now always on. There isn’t even the pause after startup before the initial few seconds of fan runtime to cool down the starter. It just runs as soon as the motor cranks. When I turn the key I can hear the solenoid click. And after startup I can hear it click off, but fan still runs.

I haven’t driven the truck more than a few miles because it’s my slow season, but I’ve idled for many hours during troubleshooting and the fan always running is definitely abnormal.

Here is a list of what I did; obviously very relatable things that could be involved.

- Remove old radiator assembly, replace with new. CAC and Surge Tank were removed as part of the process but replaced with the same existing parts.
- Replace coolant and ran the truck to suck the coolant down, topped it off. Coolant is normal level.
- Remove AC condenser, replace with new.
- Remove AC drier receiver, replace with new.
- Vacuum AC to -30 for 30 min and hold for 10 min, no loss shown.
- Recharge AC system with proper daycab ounces (46) using scale and manifold/gauges. I have a sleeper but don’t use it, sleeper lines are deleted.
- With truck off and at rest the Hi/Lo pressures are equalized.
- With fan running and AC compressor running, the gauges pull down to 15 Lo and up to about 150 Hi at 75* ambient. Which I think is in the ballpark but I’m not sure since fan is running. When compressor shuts off it goes to 30 Lo and 100 Hi or so.
- I am uncertain about AC oil but waiting to get some from the local dealer. Sanden manual says add about 3-4 oz if replacing condenser and drier and I haven’t done this. Plus all the Freon was evacuated but my understanding is this does not remove oil?

Here is what I’ve tried/verified:
- The manual fan switch is not engaged.
- Coolant level sensor is plugged in.
- Freon was vacuumed per Sanden manual and recharged accordingly (at least I think).
- Two sensors on top of the receiver drier (AC high pressure and another two prong sensor) were replaced with new and didn’t fix.
- Another thread mentioned this to confirm clutch and solenoid air were good and I did this: With key on, remove air line going into fan clutch. No air leaked out which means fan clutch was not stuck. Then, remove air supply going into solenoid. Air did leak out which means air supply was good. Then, multimeter for 12v the solenoid plug, one side should be +12 and one -12 and this was the case.
- Checked plugs at ECM and everything seems plugged in.
- Full or Empty (0 on gauges) tanks and try moving fan with truck off - cannot move it. During radiator job I was definitely able to move the fan freely.

Let me know what you think. If your suggestion involves a multimeter please help with some details on how to test it specifically as I don’t know how to use one very well. Electrical is definitely a weak spot.

Thanks!

 

Air in the Freon lines or elsewhere? I was thinking vacuuming would clear that air out.

 

Thanks sir. So I may have misunderstood the post I was following. When I remove that air line from the outlet of the solenoid (going into the fan clutch) it should indeed be spewing air? When I remove mine there is no air. This is with the key on but motor not running.

This is the solenoid I have. Air outlet at the bottom.

And since it’s rookie hour. The clutch engaging makes the fan stop, or spin? You saying air disengages the fan clutch, and me not having air to it, makes me think clutch engaging means fan spins right? So my fan is stuck with clutch engaged? Just trying to make sure I get this because my brain struggles sometimes LoL.

 

Ok. And in my case currently, the fan spins even as I press the start button. So the clutch is seemingly stuck in the engaged (fan spinning) position. Air is going into the solenoid but not coming out of it to allow the clutch to disengage?

 

Thank you! This is a quote from Sparkz from a 2011 post here which is what I followed. So did I misunderstand this, or maybe I don’t have a Horton clutch? No air came out when I removed the line out of the solenoid going into the clutch. No argument, just want to make sure I’m fully understanding!

“Horton fan requires air pressure to release.
Build the air pressure up and undo the air line to the fan clutch with the key on.
If air rushes out the fan is mechanically locked and needs fixing.
If no air rushes out, undo the air supply line to the fan solenoid. Heaps of air should rush out, indicating supply air is correct.

Unplug the wires to the air solenoid. One wire should have 12volts ignition power. The otherwire grounds out through the engine ECM.”

 

Replaced the solenoid today and problem still persists. Any other ideas from anyone?