is it because of the extra load of having to turn the compressor? or the heat radiating from the condenser? if both which is the greater cause?

 

I think its mostly from the load it puts on the engine

 

It's mostly the condenser heat. The A/C system doesn't "cool" the air although it seems like that's what it's doing. Rather, it takes heat out of the cabin air, puts it in the evaporator, moves it to the condenser, and radiates it back out into the wild. The air that gets to the radiator is therefore already 30º or 40º or more hotter than it would ordinarily be, so the "cold" water going back into the block is that much warmer too.

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"So many Mustangs, so little time..."

 

In case you aren't familiar with where the condensor and the radiator are... Open your hood and look in front of the engine. The big metal mesh thing in front of the fan is the back of the radiator (you could probably guess that). If you look from the front, you see something very similar that looks like it's the front of the radiator. Anyway along the top is a black piece of plastic. If you remove it, you'll see that there are actually two "radiators", one is the regular engine radiator and the other is the A/C condenser (you may be able to tell by looking from the side, but it's a lot easier with the plastic piece removed). So when you are looking from the front you are actually seeing the front of the A/C condenser. Now you'll see that air has to flow through the condenser first then through the radiator.

On a side note, it's a good idea to check in the gap between the two for leaves, plastic bags, etc. if you are having overheating problems. Often that area gets clogged up with debris which dramatically reduces air flow through the condenser and radiator.

 

that's my primary concern egg, the condenser is infront of the radiator so RB is right on the money, i think, i'm not sure about the load though coz v8's are supposed to be powerful engines right? but i'm no expert, anymore opinions anyone?

 

The compressor puts relatively little load on a v8 engine. As others have said, the heat comes from the condenser acting as a preheater for the radiator.

 

I think the compressor actually sucks more power than you think. Depending on what year you have (mine is an 85) the A/C systems worked pretty well to cool you off, but weren't all that efficient when it came to making use of the engine's power. It seems like it would take a few seconds at least for the load to hit the engine if the air & water had to go throught the whole system first, but if you notice, the power will begin to drain immediately when you turn on the switch. That's my un-ejubucated guess. If anyone knows for absolute sure, please post it, I'm curious, too.

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`85 Z28 5.0L TBI
Don't ever be:
Found On Road Dead!

 

Well I can feel the difference in power when the A/C is on... But load on the engine isn't why it runs hot. Preheating the radiator is. I mean, even if the A/C sucks 25 hp (I really really doubt it) so what? That's not much load to a v8 that puts out 170+ hp. It just means less power is available for accelerating.

 

I agree with Mr. Egg, Russ, RB83L69 (good post RB - you got it right! You must work in the AC field....).

Just touch the line going into the condenser. It's hot. And that's what the air passes through to cool the radiator.

 

Sounds good to me. A friend of mine who is a big "car guy" tried to get me to pull my A/C stuff out of the car since it robs power. He also said its only like 3HP, though, (he could be wrong, has been before), but that does sound about right. I don't think it would take all that much out of one of these hogs.

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`85 Z28
Bosch Platinum +4s & a nice stereo
Otherwise stock.

Don't ever be: Found On Road Dead!