Okay so when i'm driving to Long Beach which is about 20-25 mins with my windows down and air on. my water temp usually always gets to 84deg celsius, sometimes 85. now when i do the same drive with my air conditioning on, my water temp now peaks out at 80-82deg celcius. any comments on why this might be?

 

Temps are cooler because the rad fans automatically turn on with the ac

 

If your moving at a decent speed, I doubt the fans being on would have much effect on temperatures.

It's funny because I think a few people have noticed running cooler with the A/C on. On the other hand, I run hotter with the A/C on, both in traffic and at speed.

I can't explain it I always thought it was a given that most cars ran hotter with the A/C on due to the extra load on the engine and the additional heat dropped in front of the radiator by the A/C condensor. I guess in stop/go traffic the cooling effect of the fan (turned on by having the A/C on) might outweight the other factors that contribute but hey.....at least your not overheating!

 

As you said, the ac dumps hot air in front of the rad & loads the motor. The only way you can really expain a drop in temps is the rad fans.

I think even at ~ 40-60 mph, the fans do make a difference. Car runs cooler with fans on in this range. But as you said, ppl report different results.

 

kool thx for the input.