I posted a question on this topic several months ago, but I thought I'd revisit in the event anyone might have additional info.

In reading through parts of my owners manual, I have come across a section regarding 'fail safe cooling', and how the engine will begin an alternating cylinder firing sequence when it detects an overheating condition. This will help cool the motor and prevent meltdown, evidently, and will also cause the engine to 'power down' and cause the a/c to become non-functional until the engine temp is back in line.

The manual also says that some vehicles are equipped with this fail safe feature, and some are not........
Are our trucks equipped with that system?

I'm fairly sure I have experienced these symptoms while towing very steep or long grades in the summer, but my dash temp gauges or warning lights never moved........I guess I was just wondering if anyone knew this answer definitively.

Justification for an aftermarket water temp gauge if nothing else?

 

I believe that feature is a gasser-only one.

Pop

 

No, these motors do not have fail safe cooling. Oddly enough thought it has fail safe oil though.

 

I think you experienced defueling when the EGTs got to high.

 

You may have overboosted since you were going up a steep hill, and you got de-fueled. The fix is an regulator that lets the MAP sensor only see 22psi which is basically the most it can see before it defuels.

Bdrummonds - stock these truck will not defuel for egt's. The only way to de-fuel for egts is it he had an edge or banks box in it.

 

What is the name of this regulator, where is it (where would it) be located, and what kind of price / what vendor carries them?

 

ITP overboost annihilator is the name of the fooler. The map sensor is located by your heater core it has 3 wires going into it and has a line going to the 5 way spider. The fooler hooks up to the map line and just limits the boost at 22psi. Do not get a boost relive valve since it is basically a boost leak in the system, get the regulator from itp. I paid 50$ for it from itpdiesel.com

 

How much boost are you pushing when the truck seems to slow up? It only happens if you get over 22psi it will start to de-fuel and at 26psi it will throw a code and defuel alot, very noticeable.

 

The only times I've ever experienced this happening is pulling a hard grade during summer with the travel trailer in tow. I have Isspro gauges, and the boost gauge, which I have mounted into the MAP line, reads at 18-20. The reason I suspected a fail-safe situation was because I lalso lost A/C toward the top of the grade (after pulling hard for a while).

According to my boost gauge, the max I've ever seen it read was about 20-21.

Suggestions?

 

My AC will cut out on a long pull as well. I think it's tied into coolant temperature, if it gets too high because the engine is laboring up a hill it will shut the AC off to help prevent boil-over.
All three of my Ford trucks behaved in that manner.

 

You are not de-fueling then. It something else then, but i know the a/c has cut out on me before has well.

 

If I remember correctly, the AC system uses vacuum to run some of the doors and stuff. I have never had this problem on my PSD, but on my Taurus and the old F150 I had, when you would put a high load on the engine, it would loose vacuum, or make a lot of vacuum....I'm not sure. Anyway when there was a high load on the engine the AC would start to blow warm air till you back out of the throttle, topped the hill or stoped the hard pull. Not sure how it is tied together, but I know that it is all related to vacuum. Hopefully someone can take this ball and run..

 

Are you guys going pedal to the floor when this happens? I know on the gassers they have an A/C cut out switch so that when you are WOT it cuts the AC for more power.

 

Not so much pedal to the floor as the cruise control giving a LOT of fuel to climb that 6% grade for the next several miles. First the radiator fan locks up and howls and a couple of minutes later the humidity level in the cab spikes up because the AC has turned off for the time being. Once the road levels off and the rad fan quiets down you can feel the AC come back on.
All three of my trucks have been like that. Two of them were 460 gassers.

 

This is what i found for the A/c cut out switch.

The A/C pressure cut-off switch is used to interrupt the A/C compressor operation in the event of high system discharge pressures.

The A/C pressure cut-off switch is mounted on a Schrader valve-type fitting on the high pressure side of the A/C manifold and tube.
A valve depressor, located inside the threaded end of the A/C pressure cut-off switch, presses on the Schrader valve stem.
This allows the A/C pressure cut-off switch to monitor the compressor discharge pressure.
When the compressor discharge pressure rises to approximately 3103 kPa (450 psi), the switch contacts open, disengaging the A/C compressor.
When the pressure drops to approximately 1793 kPa (260 psi), the contacts close to allow operation of the A/C compressor.
It is not necessary to discharge the refrigerant system to remove the A/C pressure cut-off switch.

Perhaps when its under that much load for so long it starts to build too much pressure and cuts it off?