So on the mountain passes we see signs advising to turn off air in order to prevent overheating. Here, however, I see people saying that turning the air on will help cool the engine. What is everyones experience?

 

AC on can only add load and heat to an engine. Turning on the heater will help take heat out.

 

When you run the a/c you are adding heat under the hood by doing 3 things:

1) more electrical load from blower/compressor clutch = more load on alternator=more load on engine = more heat

2) running compressor = more load = more heat

3) Lots of heat coming off the condenser coil which is the 1st "radiator" in the air flow. You are preheating the air that is going to in turn cool your engine via the radiator

I sure don't see a benefit from running the a/c, but what do I know.

As mentioned before, running your heater will benefit you. Your getting the usage of another radiator, although it's very small. I'd have to say if your pulling a hill and the radiator can't keep it cool, you're pobably in trouble anyway. Probably time to take a look into the cooling system.

 

Turn on heater and roll down the windows.

 

I had an old chebby gasser a few years ago, and when I really started maxing it out with trailer weight, heat on and windows down was the only way to help keep it cool.

 

That is exactly what I did this late spring when my thermostat stuck. I killed the A/C and turned on the heater wide open... I decided to try limping in to the Cummins parts dept before they closed...
It SURE WORKED TOO! Was tough to stay in that cab though...
When I couldn't bear much more, I killed the fan and the temp really started climbing, so I turned it back on again.
I kept my foot out of the pedal and tried to stay at a speed close to but not really with the prevailing traffic speeds. I made it too! But had the sad news that they were out and they'd have to ORDER IT !!!
Tucked my tail and gently(!) drove to Dodge across town and paid MORE than 2x for a Cummins part...

FIrst time I've ever had to do the windows and heater trick. BTW, putting it on bi-level seemed to do a better job of cooling than recirculating all that hot air close to the floorboard.

 

the a/c on for the newer trucks forces the fan clutch to engage, to provide airflow through the condenser. that makes the fan run all of the time, not intermittently. that is why some folks recommend the a/c. with a ctd you should not have to worry about heat. maybe it is time to do some cooling system maint.

 

I don't know what you guys are driving but my truck runs cooler with the air on because it makes the fan engage and that fan just works awesome. I can watch my temps fall immediately after turning the A/C on. I know what we've all heard and read in the past about turning the heat on but it's just the opposite with these trucks.
Try getting your hands on a 180 degree thermostat and you will have temps that are actually almost too low.....

 

That's an interesting idea, basically using the AC control as an over-ride for the engine fan clutch control...

I suppose if you ran with the AC on and the heater on too, wouldn't it pull frosty air from the AC through the heater core?

 

if you notice, both of the dodgezilla's agree on something. not only great names for the trucks, but smart too.

 

Yeah, but I bet if someone named DodgeMothra showes up, Tokyo will get trashed in the brawl.

 

Great minds think alike!!!

 

i had to edit my sig for d-zillas benefit.

 

Is it the extra heat from the condensor that causes the clutch fan to kick in or is there some other mechanism involved?

If it is just the heat, isn't your clutch-fan the culpret? Shouldn't it be kicking in soon enough to prevent over-heating?

When my gen one's fan kicks in the AC gets colder, which is nice but the old style rad can't shed enough heat to make up for the extra heat and the motor does not cool down but runs near the top of the cute little inner segment Dodge has given us to figure out how hot things are.

I am going to put in a cross flow rad, will install the 3200 gov spring have got but not installed. Easing up on the pedal and gearing down help my old girl handle the heat.

Back in the pre-clutch fan days my 1965 Volvo P1800 had a monster heater core. I removed the fan altogether for winter driving. A few times I was caught in traffic jams with no fan on unseasonably hot days and just turned on the heater. It kept temps right down to normal and I enjoyed (not) my free Swedish Sauna

There are some awsome electric fans which can be found at pick a part wreckers. (I like Kar Basher's in Edmonton) for cheap. A pair of those in front of the rad can help. I run one for my AC. But a better fan clutch is probably the best idea. The heat output from a hard working AC unit is enormous.

I have seen many newish trucks blow their coolant because the owner was pulling hard up a mountain pass on a warm day. They neither geared down nor turned off the AC to give their truck a chance. I was suprised that I could overtake these trucks if I geared down early and kept the revs ahead of the fuel and heat. I know the standard tranny is a big help.

 

Hit the nail on the head. I'm not sure about the 3rd gens, but the 2nd and later have fan clutches that lock up with temperature. There is no electric clutch. The only reason you are locking up the clutch is because your heating the air before it gets to the radiator. If it's running hot and not locking up, you need a new clutch.

Even if you have a vehicle that has electric fans stock, running the a/c is not a way to get the temp down. Yes, the fan will run all the time with the a/c, but it should kick on when the water temp rises with the a/c off. Most even have variable/dual speed fans that speed way up when the temps get to a higher than noraml level.