Temperature goes up when A/C is on..

[ii_cantwait]

I have a 90 240sx with approx. 109k miles(5 spd manual). Today I was driving around with A/C on full blast and i realize that the temperature gauge was going up gradually. to the point that it went up 1 notch so i turned off the A/C and eventually returned to normal temp. What could be the problem?? Do i need to change my coolant?? Btw the coolant reservoir tank was at the minimum mark. Please help..Thanks!

[s13sr20chris]

i would try changing the coolant anyway. check to be sure that your fan or fan clutch is working properly.

[vancouverbc]

is there any connection between coolant temp and ac operation? i could see the condenser getting too hot and decreasing efficiency of rad. ie condenser fan not working. don't think bad compressor would affect water pump that much.

[NISTECH]

Its a combination of the extra load on the engine, which the compressor is a substantial load alone then combine that with the condensor fan and the blower motor fan putting an additional load on the altenator which also adds to the load on the engine.

As chris said make sure the condensor fan comes on when the A/C is on and that your mechanical fan clutch is in good shape.