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Truck Overheats with AC on while towing

On two occasions while towing our camper

the temp gauge shot up to red. When we turned the AC off temp went back to normal.

We had the condenser , radiator & water pump replaced. Thermostat is OK. You would think a diesel could handle 8,000lbs. Out of ideas!

Does the truck have a transmission cooler on it? If so, does the cooler have a separate radiator than the A/C or the same? You probably have 2 separate radiators, if the truck has a hauling package, one that cools the trans fluid and the other, the engine. When the A/C is turned on, there is a lot more heat to be evacuated, and thus a hot engine. Just a thought.

We have the HO Turbo diesel with tow package (including trans cooler). We also replaced the inter cooler which I thought would improve cooling capabilities. Whats left?

It honestly could be you are asking too much from this truck. While the 2010 Ram 2500 boasts a towing weight range between 5 and almost 6 tons, you don’t mention conditions. I guess one of them is very hot weather, another maybe steep hills? Even with great torque and a strong diesel engine, running the A/C while towing four tons up a long or steep grade is probably asking too much.
Even tractor trailer operators run fast downhill when the way is clear to gain momentum to get up the next rise. Granted they are usually hauling between 9 and 20 tons, but their diesel engines are much more powerful than yours. And running loose downhill with much more weight behind you than your truck’s brakes can stop is not an option for you. One miscalculation or unexpected event -such as a car veering from the left lane to make an exit at the last second - could easily result in a loss of control. Tractor trailers can engage trailer brakes, essentially transferring the braking duties to the much heavier trailer (while also losing a good deal of maneuvering control).

I don’t like the scenario of a five or six thousand pound pickup trying to tow and control an eight thousand pound trailer in the first place.

In any event, I would forgo the A/C in adverse conditions. You have a good truck but I think the 4 tons is a bit too much under less than ideal conditions.

I think this truck uses a fan clutch. Did they not consider that possibility before replacing all of this other stuff?

If the truck uses an additional electric condenser fan for A/C use and that fan is inoperative overheating can occur.
You mention replacing the condenser and if the A/C system is overcharged overheating can occur due to this also.

Yeah, something is unright. You should not even know 4 tons is being pulled. The funky thing is having the AC alter it.

You can’t be telling all the particulars.

I go with the fan clutch.

But you’ve also got to tell me that you watched the needle climb all the way to the red? Sorry, but what did you expect to change by the time it got there?