I've been having problems with the coolant temps getting excessively high (240 deg +) on my 6.0 2003 Exc. when towing my 6500lb toy hauler. It "appears" the fan kicks on at about 228-230deg, and signs off when the temp drops back down to 215 or so. Sometimes on long hills here in AZ (110+ ambient temps) The fan has an extremely hard time getting the temps down. I did the "blue wire mod", tying the blue wire on the fan harness to ground via a simple switch. I now can pull the temps down from 215 or so to 186 within a couple minutes of engaging the manual over ride. (haven't pulled any large hills towing with the mod...yet) I got to thinking, "Why can't I tie the blue wire to ground automatically when I engage the "tow" mode on the gearshift"? Can anyone on the forum provide/direct me to a drawing/schematic of the circuit that powers the indicator light on the end of the shift lever that indicates "tow mode" is engaged..? Generally, the only time I need the extra fan time is when towing on long hills fully loaded. I recently replaced the stock radiator, as it had a cracked plastic end tank, with a Mishimoto all aluminum radiator, hoping it would add a bit more cooling, didn't happen. Not sure why they didn't include another row of tubes, as there is plenty room for them. In any case, I would use the signal that turns the tow mode indicator on, through a FET or relay to provide the ground path so the cooling fan is full "on" when pulling in tow mode. I can pull things apart myself, but if some of the hard core Ford guys on here can tell me what I'm looking for specifically, I could pull that signal from the steering column without disassembling the shifter lever itself...

 

Did the replacement have the same number of cooling rows as the stock one?

Did you consider the pump?

Interested to hear the answer. Grounding the tow/haul switch.

 

This is how to engage T/H on startup, it tells you what wire triggers the PCM:
https://www.ford-trucks.com/forums/3...ml#post2210897

Problem is I think the light is controlled separate of the signal from the momentary switch, so not sure how to get the "on" signal from the cluster, only how to catch the initial signal turning it on.

Use the signal to power a really long delay relay (12V timer?) that only grounds the blue wire?

 

The mishimoto radiator is known to not increase cooling efficiencies due to smaller than stock connection orifices according to some. There must be some validity to this as mishimoto has responded with a revised design in the last few months.

 

The Mishimoto, even though it appears to have room for another row of cooling t
ubes, has the same as OEM..Not sure how to identify if the water pump is at fault,. typically a leaky seal would indicate problems with the water pump..

 

Great instructions. I think the most direct way for me to implement this is to take the signal that illuminates the end of the shifter indicating "tow mode" is on, and use that to drive a low voltage relay of some sort. Anyone ever had the shift lever handle apart where that bulb (or LED) is located..?

 

Does the Ex have a different shift ****? There's no light in the T/H shifter on my truck, hence the issue with the impulse signal from the switch to the cluster.

 

My '03 has what looks like a regular column shifter, with the exception of the "tow mode" mom switch and illumination indicator on the end of the stalk...

 

Weird, I didn't know the Ex was different. Yes the signal for that light would be constant, none of the mess with a timer and the momentary signal then.

 

The ex's are the same in the shift handle department as the same year of truck. He has an 03, and the 03 6.0 ex and trucks used the 7.3 shifter handle where it lights up on the end. 7.3 light up overdrive "off" on the end vs what the 6.0's light up with for tow haul.

Another option,
I used the factory fan harness ends on my fan override switch. I bought both of the ends(engine side and fan side) and made a plug and play jumper harness. I left the wire lead thats connected to the blue wire out of the connection and ran a 14/2 wire loom to the cab and connected it to a on-on switch. When the switch is in the down position the system is on automatic mode and the pcm is controlling the fan. When I flip the switch up its in manual mode.

 

The fan kicks on at 228??? I'd be starting with a fan clutch. I've been playing with the lifetime Oreillys fans. They are quicker to respond than oem. They kick on at 208 (which I'm really liking), and kick back off at 198. Oems are normally on at 218. They also run like a ****** when the ac is on. I think they are more reactive than oem ones. Sorry to hijack,, but a healthy cooling system doesn't need help. I've been up most all grades with most all configurations of loads. Just make sure you aren't masking an issue with a mod.

 

I never hear my fan run even with the ac on

 

I'm with run60run that the fan speed control is not functioning properly when the fan is not on high at 217-218 f. There should be no need to do the fan override unless you really are towing heavy and want to start cooling well before and all through a big hill. If the fan really does bring you down to those temps I doubt the water pump or anything else in the system is bad. That's where to look first. How new is the belt, idler pulleys, tensioner?

 

What is your Fan RPM when it's fully locked up (FSS on the Scanguage)? It should be showing higher RPMs than the engine and screaming loud when its fully locked up. If not, you've probably got a fan clutch issue.

It should be going to full speed right around 218-220.

Run6.0run is that a electronic clutch like the stock or a mechanical? Stock is controlled by the computer so I wouldn't see it coming on early like you mentioned?

 

It looks to me like the oem fan is not as responsive as the other. I understand that our conception up to now was the fan comes on at 218. However,, do we know it isn't programmed to come on earlier,, and the clutch is slow to respond? I didn't used to think that. However I've spent some time with the other clutch and it's very predictable. Changing the clutch alone should not change the programming at all. Maybe the aftermarket clutch needs less heat (heat isn't generated through ambient temp,, it's voltage that heats the clutch locking it up). If you command the fan on they always take a while to respond. I guess this wire mod would help test the quickness of the fan to respond.