Air conditioning problem 2006 F-250 6.0 Diesel


Enjoy the show…Listen to it as much as I can. Never figured I have to write you…but here I am.

I bought this truck new in October 2006 while in Nebraska. First REAL test of air was while I was in southern California april-june 2007. I have two different problems.

1) takes LONG time for the air-conditioner to cool down vehicle. if outside temp is 90F or above the vehicle does not feel comfortable until I have driven roughly 25 miles. This with max-air selected. the red/blue temp selector is in the max blue position because the temp selector has no effect on air temp coming out, but restricts the flow if warmer temp is selected (FORD design). Anyway, I feel the vehicle should be able to cool the passenger compartment quicker than it does. And YES GUYS, I have the windows closed! Friends that have Chevys and Dodges cool MUCH faster.

2) 1st time I noticed THIS problem I was in southern California I was headed east on Interstate 10. There is a long steep upgrade. I have the max towing package that came with this vehicle I believe it is the 13,500 towing capacity. I have a 33 ft travel trailer and was pulling it at the time. Probably 10,000 pound weight loaded. before we started the assent we were perfectly comfortable. My wife was in the vehicle. I don’t think that is the root cause of the problem but … Anyway as I was going up this grade (mountain) it was as if the air-conditioning compressor stopped. The blower was kicking out warmer air. when we reached the top of the assent we were both sweating. Nothing going on guys…Just sitting there. Apparently there is a compressor cut-out relay that when the engine feels excessive load it activates. Is there anyway to bypass this function. It is as if this DIESEL engine is incapable of pulling the load AND the air-conditioning compressor.

Attempts to take it to a Ford dealer ( not the selling dealer) ended with the response that the air-conditioning is performing as it is suppose to.

any words of wisdom?

Steve Toussaint,

Alton Illinois


Do you have any pressure figures for us to evaluate? A trip to a AC only shop might be in order. Get a thermometer to put in the center outlet so we can evaluate outlet temp,get values at different fan speeds. Make note of the humidity on the days you give the values.Friends F250s (year model2003) do not display any concerns (live in Bakersfield area) Diesel engine dont know if its 6.0. And they have the 4 door body style


when you first get in your truck use the economy air setting that uses fresh air, that will allow the hot air in the truck to get out and get fresh air, then switch to max. only using max, you are recerculating the hot air, it takes longer to cool. works on my dodge. as for the auto shut off under hard acceleration or heavy load, it might make your truck run hot if disconected.


When they started trying to make trucks aero dynamic, they put huge slanting windshields. They act like a big greenhouse, and on extended cabs all that extra roof doesn’t help much either.

One thing that hurts diesels in the ac department is the fact that the engines turn lower rpm’s than gas thus the compressor runs a little slower. Makes a big difference especially on extended cabs than need more volume from the ac. My Dodge diesel is the same way for what it’s worth. Slow to get cool. The best thing I’ve found to do is run both front windows down and open the rear slider and let the hot greenhouse air flow out. The outside air isn’t much cooler, but 20 to 30 degrees cooler at least helps.

As far as the compressor shutting down, I have a problem believing that’s because the engine is overheating. A diesel has enough power and torque that it shouldn’t know if the compressor is running or not. It leads me to think the compressor is low on freon.



It sounds like you might have a restriction in your A/C system, an incorrect amount of refrigerant, or something blocking the evaporator core. If you had your foot on the floor while towing up hill, that would explain the A/C becoming warmer, but I think it’s more likely that warmer engine temps made it harder to cool down that condenser. Maybe your fan clutch isn’t operating properly. I agree that you should take it to an A/C shop and see what they think. They’ll look at pressure on the high and low sides of the system along with output temperature and will be able to tell you what’s up. Good luck!


With the caveat that I don’t know anything about heavy PU powertrain management, modern Ford (and other) passenger vehicles typically have a WOT cutout for the AC compressor. If you have your foot down hard on the ascent, the compressor might be supposed to be shut off. I don’t know if it is really 100% throttle opening or more like 99 or 95… You can probably have a custom tuner change the feature in the PCM programming so you cut off the AC at a higher throttle position or not at all. You can do it yourself with a switch to the AC WOT cutout relay and save at least a couple of hundred $. I have been told that this is a feature to preserve the belt as much as provide power, but I am skeptical about that.

I have a vague memory of a TSB for Ford Superduties that I saw a few years ago. It might not even apply to a 2006. It had to do with cooling capacity in hot weather. The solution involved installing an additional wiring harness and coolant diverter valve. The wiring controls the coolant diverter valve cutting off the coolant flow to the heater core unless full cold (blue) was set. It seems like the blend door is not totally effective in diverting air flow from the heater core. I have noticed that the air coming from the panel vents is commonly measurably higher in temp compared to the air flowing past my windows.) I suspect that air flow slows down in the warm position because there is more resistance through the heater core. Now that I read your post again, " …the temp selector has no effect on air temp coming out, but restricts the flow if warmer temp is selected (FORD design)." maybe you already have this feature and the MAX setting is what is directing hot coolant away from your heater core.

If no one here has anything to add, I would head to a Ford truck site. One that caters to larger and Diesel ones would be preferable.

Just one added note. You have probably already figured out that if the weather is humid you are best off starting out in MAX since the only thing that does is recirculate air rather than bring in fresh. If the air is dry, you are best off flushing out the hot air in the cab with slightly cooler outside air.


Why would a WOT AC cuttoff be neccessary on a 2006? Compressor horsepower requirements on todays compressor are not significant (going by the very small gain in gas mileage with AC off in comparison with AC on). Now there is a long steep grade on Interstate 10 heading east out ofL.A. (maybe around Palm Desert exact location not important) There are state highway signs warning “turn off AC to avoide overheating” I think these signs are dated. There is no reaso to suspect that Ford has underengineered the cooling system on its best selling vehicle. Long steep grade,high outside temp,towing a trailer in spec (in regards to weight) and AC blasting full it should handle it all


“There is no reaso to suspect that Ford has underengineered the cooling system on its best selling vehicle.”

I would expect it. They mis engineered every darn thing else on that engine.

Seriously, I can’t think of a reason to have an ac cut off on an engine with the kind of power that diesel ought to have. Were not talking about a 150 horsepower 4 cylinder straining for all it’s worth to haul a minivan across a mountain. We are talking about a V8 diesel with over 300 horsepower and supposedly from Ford, around 600 ftlbs of torque. It ought to be able to pull 20 ac compressors and not notice them.

There’s about a 50% possibility the 2003 truck has a 7.3 diesel in it, in which case, it’s got an infinitely better motor than the 6.0.

I’ll stick by the statement that a longer than average time to cool the truck down is somewhat normal in these newer trucks. My old 95 could hang meat when the ac unit was running but it had standard cab and a pretty much flat front windshield. The newer ones with the longer front windshields are big greenhouses. The longer extended and super cabs need more ac capacity, but they put the same size unit on them as they do the single cabs. There’s also a significant difference in the capacity for cooling on the newer R134 systems than there were on the older type freon.

The fact that the compressor is shutting off doesn’t sound to me like it’s acting normal. I believe it’s low on freon, leaking or in some manner not running right.



The difference is 7percent between R12 and R134


I’d say when you couple that along with slower compressor speeds on a diesel because of the lower rpms on the engine and the modern style trucks it all adds up.