Cooling Fan Switch

[JBB1970]

I was thinking about the cooling fan while driving my freightliner truck the other day.

On the Semi, you have a switch to manually trun the engine cooling fan on should you want to. You can also leave the switch off and just let the truck decide when to kick the fan on.

Is there a way that I can do the same thing on my 6.4? I would like to have that option.

[JBB1970]

I guess this is not possible judging by the response

[jesilvas]

If it's electric I'm sure you could

[gary2070]

I think that fan is computer controlled and you might be asking for problems if you put a switch on it. Now you might be able to install a pusher fan in the front and wire it on a switch.

[Big Angry Hillbilly]

You could probably wire it to duty cycle the fan on when you wanted to, but I bet it would fling the check engine lamp on if you did it, or fry the PCM if you had to feed it voltage/ground. Let me check it out and I will get back to you.

[JER-1]

SUBBED
Great for towin in the mountains
JER-1

[dieseldan2005]

Its too bad these fans aren't an on/off style like the horton fans in semi's. It would save big time on extra fuel and wear and tear on the belt and accessories. There are a lot of things i wish my psd had that my peterbilt has.

[JBB1970]

Thanks Hillbilly, I would appreciate it. I was thinking of hooking one of them up through the upfitter switch.

[Big Angry Hillbilly]

That MIGHT not work, as the upfitter supplies power. You would likely have to wire in an additional relay to switch ground, as it's likely ground controlled. I'm looking at the wiring diagrams, workshop manuals, and powertrain/emissions control manuals, and not getting a clear cut answer of what controls the fan, be it power, or ground.

All it tells me is that it's a "pulse width modulated" control circuit. Gee, thanks guys.

I would ASSUME it's a ground modulation, seeing as how it's controlled from the PCM directly, not through any relays or junk. And of course, there's no label on the PCM connector diagram to see whether it's power or grounded that turns it on/off. There's TWO pins for it at the pcm connector.

Let me do some measuring this week and see what I can come up with. I am not entirely sure if there's going to be a good answer, or at least what you're looking for, unfortunately. I think at the very least we're going to turn a check engine lamp on doing this, as it will see that as a short to ground or power, I think. Depending on what we have to add to make the clutch come on.