Manual override switch for eng.fan

[AutoJim]

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Can you elaborate a little about this? Would an aftermarket chip/programmer alter the information for the fan, and if so, what benefit to them would it do? I'm not being sarcastic...I'm just interested.

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Joey, I seriously doubt an aftermarket programmer would consider going after the fan calibration unless they thought they could get more horse out of the engine by reducing parasitic losses and thus delayed the fan engagement accordingly.

The problem with that is that the CAC actually can pull the intake charge temp down enough with the fan engaged that the ECM will then add fuel and timing and the net result is a RWHP *gain*. This is something I've actually seen happen on an electric absorbtion chassis dyno in a climatic wind tunnel (which is designed to precisely simulate actual "driving down the road" conditions including road load and wind speed and volume), and you're not likely to see it on one of those Dynojet or Mustang inertial chassis dynos. You will, however, benefit from it when actually going down the road pulling your trailer up that mountain.

Real life is not an inertial chassis dyno. [img]/ubbthreads/images/graemlins/smile.gif[/img]

No, what is likely is that the programmer or chip will intercept some of the input signals -- such as ECT and/or IAT, and "alter" them before passing them on to the original ECM, which sees a lower temperature than is actually present and thus a) adds fuel and timing, thus making more power, and b) doesn't engage the fan because it doesn't think it's necessary.

Hope this makes some sense,

[OCOMOF05]

Has anyone thought about rinsing out the radiator fins etc.. or check the coolant for clean cooling system.I would do these simple actions just to ensure maximum air flow and cooling.

[himark]

Well since its been asked and I have searched for the answer I see nobody has elaborated and actually done this. I am going to put a switch on the fan today and will report how it works out. Question is weather or not it will set a code. We will see. As for the comments why you would want to do this? the 03 trucks DO have a issue with fans working. I have had mine into Ford and they said "all checks out" but yet I can BOIL it pulling heavy slow mtn. grades without a programmer and only running 45 mph, so I think I can run it better than the PCM by just watching a gauger or listen for the sound of boiling water. Yes there are times you need a switch.

[andrewbalser]

I did it on my 03. #1 Reason was I needed a project for the day. Benefit of the project was having more air blowing over my A/C condensor unit while I sit in the truck in high idle air conditioning. With the fan engaged, and on high idle, my truck sounds like one of the rigs sitting at the truck stop. On high idle, I can engage/disengage my fan. Sure the fan is activated 'some' when AC is on, but when it's hot, more is better and the PCM doesn't give you more the hotter it is outside. IIRC, there is a blue wire in the harness that connects at the fan shroud(driver side), but near the top. If you carefully splice into that blue wire, and just supply 12v to it when you want the fan to come on, you will get FULL FAN action, over the course of the next 30 seconds. It takes it several seconds to fully engage the clutch, as it also does to disengage. I NEVER use it for cooling the truck, but when I put it in, one thought was that it sure couldn't hurt, should the truck fail to cool itself off for whatever reason. I don't know that it threw a code or didn't throw a code, but I have never had a C/E/L.

[taztruck]

On my 03 250, I added a switch to the light blue wire in the fan connector at the top of the fan shroud. This connector is a five wire connector and the light blue wire receives a GROUND connection from the PCM when it decides that the fan needs to be turned on. After turning on the switch to send GROUND to the light blue wire, the viscous fan clutch heats up (it will take 20-50 seconds or so to fully heat up) and the fan will engage and run with a lot of sound!. After turning off the switch, the viscous fan clutch will still be hot, so it takes a minute or so for the fan to slow back down. Again, the light blue wire is for GROUND only, not 12 volts! Also, the heater in the clutch draws about 1.25 amps or so. I used a 16 gauge wire and a small toggle switch. No code has ever been set!
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[Pharkor]

FWIW:

For any truck that did NOT come with the "Factory Towing Package" on the unit, you can simply install a new factory cooling fan "clutch" assembly or even have the "stealership" put one in for you - that will fix your cooling problem for when climbing up hills, towing and plowing.

As well, for anyone that mounts a snowplow .... I STRONGLY suggest that you replace the fan clutch assembly before plowing and certainly before driving down the highway for any distance greater than 3 miles ....

... if you do NOT have the "Plowing Package" Fan Clutch assembly installed and you drive down the highway with your plow installed ... you are running a HUGE risk of overheating your truck and could cause some serious damage to your engine. In a "pinch", you can try to keep your plow blade as low to the ground as possible when traveling - but that can be dangerous as well ... but traveling with your plow in the "UP" position is just not an option if you want to avoid burning up your engine.

... seriously, just replace the fan clutch assembly with the unit that comes with these trucks that have the factory "plowing" package in/on them and you'll save yourself a WHOLE lot of problems and no matter how cautious you are ... eventually ... you will make the mistake of driving too far with your plow blade raised up too far and you will run a serious risk of burning up your engine.